The invisible hand in sexual evolution

Section one: The invisible hand in evolution of human society
Evolutionists freely admit that the origin of the sexual process remains one of the most difficult problems in biology. Earth have existed for billions of years before the appearance of human, and our first human ancestor just showed up in 59:58.2, if we see the earth's history of 4.6 billion years as one hour, not to mention that the first modern human appeared about one second ago. Before men appeared, what happened to the earth and how human appeared? I do believe that our human evolutionary pathway had only one way, but now we are unable to relive it again, and the only way we can approach the truth is deduction depending on the existing evidence (maybe like the Science of Deduction by Sherlock Holmes). This is like the uncertainty in measurements that we never can get the true value of weight, but the only thing we can do is to use the scientific method to characterize it, through our rational cognition to approximate its true value, whatever in natural science or social science.

1. Unity of natural sciences and the social sciences

There is even no distinction between sciences and social sciences in 16th century, and they are not separated from each other yet. Thomas Hobbes did a lot of work on optics at the beginning and then really did some absolutely path-breaking work, and he can’t be classified in any of the disciplines. He tried to develop a theory of society which begins actually with biology, with biological processes, and build it up gradually from biology to understanding of the social, of the individual, and from the individual to understand society, and he advocated the way how to understand human existence is start with bodily functions, and move from bodily functions to politics and philosophy. It is really by the late 18th century, that people are beginning to identify as studying society or human behavior, but still multidisciplinary.

That is where my inspiration comes from. I think the purpose of division in sciences is for an in-depth study in some specialized field, but at the macro perspective, I do believe the unity of natural sciences and the social sciences. The law of nature works in the former, controlled by ruthless evolutionary rules, and the development of human society is far behind it. So far we humans are still exploring the natural law step by step, but we can not understand everything well in big nature (I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me – by Isaac Newton). Human-specific social order and civilization comes later, also controlled by ruthless evolutionary rules, but after human have a little certain self-consciousness. We can start from our self consciousness to study social science much easier, because the scope of the study is just limited to humans. I do think we can get something mature from our human-specific social order to apply to understand the natural law. Maybe it can help us closer to the true value in ruthless nature. In short, we also can start with rules of politics and philosophy, and move back to bodily functions, biology or biological processes.

2. The division of labor
The division of labor is a subject which has fascinated social scientists for millennia. In the history of human evolution, if we identify there is an invisible hand to dominate the human evolution, I think that is the division of labor. Division of labor and cooperation, in the evolutionary road, runs through the whole path both in the macro and micro. There are some our founding fathers of sociology who ever researched it, like Plato, Durkheim, Adam Smith and Marx, and here we are going to review some main ideas about origin of division of labor.

2.1 Adam Smith’s view
In the first chapter of “The Wealth of Nations”, Adam Smith talked about the division of labor. He thought there are three main advantages of division of labor: “first, to the increase of dexterity in every particular workman; secondly, to the saving of the time which is commonly lost in passing from one species of work to another; and lastly, to the invention of a great number of machines which facilitate and abridge labour, and enable one man to do the work of many.” In the chapter Ⅱ“Of the Principle which gives occasion to the Division of Labour”, Adam Smith gave his explanation about the origin of the division of labor: It is not originally the effect of any human wisdom, “It is the necessary, though very slow and gradual consequence of a certain propensity in human nature which has in view no such extensive utility; the propensity to truck, barter, and exchange one thing for another.”“Give me that which I want, and you shall have this which you want, is the meaning of every such offer; and it is in this manner that we obtain from one another the far greater part of those good offices which we stand in need of. It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages.” In short, Adam Smith thought the motivation of this propensity is self-interest and self-love, and obviously this is utilitarian thought. Speaking of utilitarianism, we must talk about John Stuart Mill, and central idea in his book “Utilitarianism” is our human are seeking pleasure and try to avoid pain, and correct action is to maximize pleasure and minimize pain. Compared with his game theory, I like these words more “Genuine private affections and a sincere interest in the public good.” Frankly speaking, before Adam Smith, Thomas Hobbes' view was very clear: “mankind is not inherently benevolent, but rather self-centred and competitive.”

2.2 Marx and Engels view
Unlike Adam Smith’s view, they argued that there was a sexual division of labour before systems of agriculture developed. In the period of barbarism, men lived in the woman's household, and the sexual division of labour already existed. Women were responsible for subsistence in terms of reproduction and production and preparation of food and other goods – in general the household responsibilities; men were responsible for obtaining food and doing "productive work". Whether this is correct, or why this developed is not clear. Engels may have viewed this as a natural division of labour, because he considers the origin of this division to have originated with the different functions of male and female in the sex act. In short, according to Karl Marx, the original division of labour occurred in the family, because of the different functions between two sexes by natural, and then with the development of productive forces, division of labour moved from family to social, and then finally mental and manual labor separation.

2.3 Marx's theory of alienation
Marx argued that increasing the specialization may also lead to workers with poorer overall skills and a lack of enthusiasm for their work. He described the process as alienation: workers become more and more specialized and work becomes repetitive, eventually leading to complete alienation from the process of production. The worker then becomes "depressed spiritually and physically to the condition of a machine". About the abolition of the division of labor, Marx theorized that the existence of classes originated in the division of labor, and the division of labor, as it has been known up to the present, will completely disappear, especially between mental and manual labor with the development of the productive forces.

3. My views
3.1 First, I don't agree with Marx that division of labor is a product of development of productive forces, and the emergence of the division of labor is much earlier than the emergence of human beings. Hunting within a group is very common in animals, for example, wolf-pack catch prey as collective behavior in hunting strategy, some tracking, some pursuing and some encircling prey. Why is that? Don't you tell me because they like to get along with each other? I do think the real reason for this division of labor in hunting strategy is just because the poor individual ability.  Richard Dawkins said that the important idea of reciprocal altruism is the principle of 'You scratch my back, I'll scratch yours' in “The selfish gene”. Apparently, division of labor not only belongs to human beings. Essentially, we can consider it as a symbiotic mutualistic relationship. Now Wikipedia gives us that mutualism is the way two organisms of different species exist in a relationship in which each individual benefits. Similar interactions within a species are known as co-operation. Key word: two organisms of different species. I think this definition is too rough, we should zoom mutualism into gene and cell level. Please remember mutualism is very important point in my sexual evolution deduction.

3.2 Second, I admit the division of labor appears in the two sexes because of natural different body functions, but just in macroscopic sense. In fact, the original division of labor occurred both in genes and cells. You can consider it like this: in genes level, since gene can control protein synthesis, and different genes synthesized different protein, so they have to work together for living and reproduction. I agree with Dawkins'more radical idea that each one of our genes is a symbiotic unit, the reason genes cooperate with one another, not because they are our own but because they share the same outlet— sperm or egg—into the future. If any genes of an organism, such as a human, could discover a way of spreading themselves that did not depend on the conventional sperm or egg route, they would take it and be less cooperative; in cells level, every human started from a single-cell zygote, and then developed from single-celled to multicellular through mitosis, and then cell differentiation happened after there are enough cells. Essentially, cell differentiation is a kind of division of labor on a cellular level. After a series of division of labor, various independent organs formed. What happened then? Cooperation, a kind of symbiotic mutualism, they began to perform their own duties under this game rule, because they are on the same boat. So the system is formed. Human body is made of ten different systems and all the systems require support and coordination of other systems to form a living and healthy human body.

3.3 Last, basically I agree with Adam Smith's view on origin of division of labor: it is not originally the effect of any human wisdom; it is a kind of exchange, but there are two serious consequences of division of labor Smith missed.
3.3.1 One is the disadvantage of interdependent.
In Economics, global economic integration is an irresistible trend, and each country plays a unique role in big family, and it works fine until one part breakdown. For example, if all textiles are manufactured in China, years later no other country would know how to make textiles. What if one day something mutates in China and no longer supply textiles any more? What happened? Don't all people around the world have to wear leaves again? What can we deal with it? Let us look at the genes strategy: Diploid. Some people said that the emergence of diploid just prepared for sexual reproduction in the future. I don't agree with point at all. I do not think any of evolutionary had a foresight, it is like the reform of human society, and the only purpose of reform is just for solving the current problem. This also applies to evolution, and any reform in evolution is just for solving the current thorny issue, if this reform really becomes cornerstone some day, I think it is indeliberate. I admit the emergence of diploid is the premise of Meiosis, but diploid organisms still with asexual reproduced are very common in nature, and in the early period of diploid, there is no meiosis at all. I do think the diploid strategy the genes used is for preventing the disaster of Haploid mutation. What can we learn from genes? Don't put all your eggs in one basket, at least you should find second basket, and backup is very important strategy. In Medicine, I mentioned that human body is made of ten different systems, as human evolutionary process of cell differentiation has been solidified, and if any one of these systems is damaged, human body will become unstable and this lack of stability will ultimately lead to death. The instability caused by damage of one system cannot be stabilized by other systems because functions of one system cannot be performed by other systems. For example, once I lost my arm, I lost it forever; once my heart break, I would die immediately, because human don't have organ regeneration ability. There is also an exception: the worms have the unusual ability to regenerate body parts, including a head and brain, following amputation. I do think research on worm's regeneration ability is very helpful for human organ regeneration, and the stem cells research is on the way. I think that is why Marx said the division of labor must produce occupational dementias, and we can consider the worms with the organ regeneration ability as a sort of non-complete organ differentiation. Every coin has two sides.

3.3.2 The other consequence of division of labor is injustice.
In fact, I think Adam Smith realized this problem, but he just called it as “Fate”. Adam Smith uses the term “invisible hand” only three times in his writings. Each time he is using it in a different sense. Here I give you my understandings about the three. Three senses of “Invisible hand” by Adam Smith
“Invisible hand” in first sense:
One it means simply the invisible hand is the free unregulated market that is how we normally understand it today. In economics, the invisible hand of the market is a metaphor conceived by Adam Smith to describe the self-regulating behavior of the marketplace. Smith assumed that individuals try to maximize their own good (and become wealthier), and by doing so, through trade and entrepreneurship, society as a whole is better off. In "Wealth of Nations" he states: "Every individual necessarily labours to render the annual revenue of the society as great as he can. He generally neither intends to promote the public interest, nor knows how much he is promoting it ... He intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for society that it was no part of his intention. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good."

“Invisible hand” in second sense:
Second he is using it as the hand of God. I think it means the division of labor and cooperation based on Egoism. Due to individual's capacity limited, genes, cells or individuals have to establish various cooperative relationship as alliance with someone useful to achieve maximum own benefit, whatever in living or reproduction, so we can say that the division of labor and cooperation is spontaneous. Dawkins said that “We are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes, but 'we' does not mean just people. It embraces all animals, plants, bacteria, and viruses. The total number of survival machines on earth is very difficult to count and even the total number of species is unknown. The replicators that survived were the ones that built survival machines for themselves to live in. A survival machine is a vehicle containing not just one gene but many thousands, and it got bigger and more elaborate, and the process was cumulative and progressive.” I think the hand of God is the evolutionary path that genes have to form an alliance with each other to built survival machines better and better for themselves to live in. Dawkins'theory of “the selfish gene” and Adam Smith's “self-love” are unified, one is just from a microscopic view, and the other is from macroscopic view. I think that is why Adam Smith lived in the 18th century, but Nucleic acids were discovered by Friedrich Miescher in 1869, and American biologist James Watson and English physicist Francis Crick discovered DNA in the 1950s. The reason why “self-love” theory didn't apply into genes level is Smith didn't realize the existence of genes at his time. It also works in country level, “there is no permanent Friends or Enemies, only permanent interests.” I think the meaning behind this famous not only apply to politics.

“Invisible hand” in third sense:
Third Smith is actually using it as the hand of Jupiter as the bad hand, as the fate. If we say the hand of God means the relentless evolution rule "survival of the fittest", we can consider the third hand as the injustice under the hand of God, due to the division of labor and cooperation based on the selfish genes. On this point, I agree with Marx's argument that division of labor must generate conflicts of interest between persons and groups. Besides, here I add something more that division of labor also generates the conflicts of interest between genes and individuals. It is not hard to understand, because their have different purposes. The purpose of gene is its immortality, so some genes with different functions come together to build various survival machines for living in under the rule of mutualism. We can consider gender differentiation as an important result of the division of labor, and basically, I agree the Lottery Principle, and compared with asexual reproduction, the main advantage of sexual reproduction is biodiversity, but with the further division of sexual and gametes differentiation, this reproductive strategy must inevitably lead to unfairness. Of course, the genes don't have any foresight as same as lottery, they don't even know which combination will win in the game of "survival of the fittest", but it doesn't matter, because genes have their wave tactics, as long as one combination survives, they will spread their genes to every where as soon as possible.

For example, genes generate one hundred kinds of combinations, only one would survive, do you ever think what if you are the one of the 99? What are we? Gambling? Or mice in lab? Maybe the genes would say “I don't care about individuals called survival machines at all what I build, you are all experimental, I only care myself.” Who cares? I care. It is not justice for individuals. This reminds me a quote by Soren Kierkegaard“Truth always rests with the minority, and the minority is always stronger than the majority, because the minority is generally formed by those who really have an opinion, while the strength of a majority is illusory, formed by the gangs who have no opinion -- and who, therefore, in the next instant (when it is evident that the minority is the stronger) assume its opinion... while truth again reverts to a new minority.” The majority can't change the history, just follow, and only minority who have independent mind propose a new idea and then spread it. Years later, after people realize its correctness, they become majority, and then there is another minority jumping out. This is not only the evolutionary history, but also the history of mankind, like Jean-Jacques Rousseau's main point education is negative education, is to get rid of education what people got. Simple genes repetition does not make any sense. Injustice after division of labor
I agree with Dawkins that “An average gene will spend approximately half its time sitting in male bodies, and the other half sitting in female bodies”, but this 50-50 just works fine for genes, not for individuals? In some species, such as many species of coral reef fishes, sex change is a normal anatomical process. Clownfish, wrasses, moray eels and other fish species are known to change sex, including reproductive functions. The more genders differentiation, the harder the sex change. Do you ever think why many fishes can have sex change in one life? I will explain that later.

Injustice between two genders:
Here I don't want to talk about violence against women, because that is a crime at all. Let's have a look at two points.

One is orgasm. Apparently, men's orgasm is directly related to reproduction, but so far women's orgasm is still in bullshit. If you were born as a girl, it means you are destined to be a receptacle for penis in the rule of reproduction, and you have to lose your right to experience the last shiver spreading to your body's peripheral. What's more, you have been brainwashed to believe that you are a mature woman only if you can get so-called bullshit multiple orgasms from penis penetration. It is not just injustice, but a deception under the purpose of Evil.

The other is rearing strategies. Among birds and mammals these cases of paternal devotion are exceptionally rare, but they are common among fish. Why? I do also agree with Trivers's 'cruel bind' as same as Dawkins: “Land animals like birds, mammals and reptiles, cannot afford this kind of external fertilization, because their sex cells are too vulnerable to drying-up. The gametes of one sex—the male, since sperms are mobile—are introduced into the wet interior of a member of the other sex—the female. So much is just fact. Now comes the idea. After copulation, the land-dwelling female is left in physical possession of the embryo. It is inside her body. Even if she lays the fertilized egg almost immediately, the male still has time to vanish, thereby forcing the female into Trivers's 'cruel bind'. The male is inevitably provided with an opportunity to take the prior decision to desert, closing the female's options, and forcing her to decide whether to leave the young to certain death, or whether to stay with it and rear it. Therefore, maternal care is more common among land animals than paternal care. But for fish and other water-dwelling animals things are very different. Many fish do not copulate, but instead simply spew out their sex cells into the water. Fertilization takes place in the open water, not inside the body of one of the partners. If the male does not physically introduce his sperms into the female's body there is no necessary sense in which the female is left 'holding the baby'. Either partner might make a quick getaway and leave the other one in possession of the newly fertilized eggs. Because of the diffusion problem, the male must wait until the female spawns, and then he must shed his sperms over the eggs. But she has had a precious few seconds in which to disappear, leaving the male in possession, and forcing him on to the horns of Trivers's dilemma.” How vicious they are! How cruel the battle of the sexes is!

In fact, many philosophers have argued women's tragic situation, like in the epigraph to the second volume of “The second sex”:‘What a misfortune to be a woman! And yet the misfortune, when one is a woman, is at bottom not to comprehend that it is one.’says Kierkegaard, “Blessed art Thou, O Lord our God, king of the universe, who did not make me a woman.” Jewish men have recited this blessing for centuries, and even the first among the blessings for which Plato thanked the gods was that he had been created free, not enslaved; the second, a man, not a woman, and John Stuart Mill thought since women can not own property, and in fact their husband can use them for their sexual desires they are even worse than slaves.

Injustice during same sex:
In the animal kingdom, male-male competition for mates is very fierce. To take an extreme example, in one study of elephant seals, 4 per cent of the males accounted for 88 per cent of all the copulations observed. In this case, and in many others, there is a large surplus of bachelor males who probably never get a chance to copulate in their whole lives. But these extra males live otherwise normal lives, and they eat up the population's food resources no less hungrily than other adults. From a 'good of the species' point of view this is horribly wasteful; the extra males might be regarded as social parasites. If you are a male, but small and thin, you are destined to lose your right of mating.

All these injustice are the results of division of labor. In fact, Darwin mentioned the words “physiological division of labour”in“Origin of Species”Chapter IV Natural selection, but he didn’t go to further at this point. I do believe that is what Adam Smith means as“Fate”, in Smith life, he, as an individual machine, must meet something helpless and he can't change it at all in his period. It sounds like fatalism, right? I am a female and born in“New China”, and it is not my choice, but my fate, right? If everyone says yes to current rules, we our human can't move forward any more. So I prefer to understand Marx's theory of elimination of division of labor as pursuit of fairness and justice.

Section two: The invisible hand in biological evolution

Next, I am going to apply all these rules we have got from human civilization, like Division of labor, Symbiosis, Self-love and Utilitarianism and Unity of micro and macro principles, to gene level and biological processes, and try to find the life evolutionary path. All things are interlinked.

First of all, I have to make announcement that I prefer Dawkins' 'survival of the stable' rather than Darwin's 'survival of the fittest', otherwise there are no a wide variety of species in the world, but only human beings. Secondly, I want to illustrate my views from the following views:
1, Life evolved from unicellular organisms to multicellular organisms.
2, Life evolved from binary fission to mitosis then to meiosis, and from haploid to polyploid.
3, Life evolved from asexual to sexual reproduction, and from isogamy to anisogamy.
4, Life evolved from cold-blooded to warm-blooded, from aquatic to terrestrial, from  in vitro fertilization to in vivo fertilization.
5, Life evolved from oviparity to viviparity.

1 Unicellular organisms Multicellular organisms
1.1 In cells and organs level
I think it is not hard to understand, look at ourselves, as the most advanced life on the earth, but so far we still retained the evolutionary shadow and started from a single cell – Zygote which every one came from. One zygote started to replicate itself through mitosis, and then became two and four and eight and so on, after enough cells gathered, they started the cells differentiation. This cell aggregation is definitely not simple cell accumulation like stones, but rather shares the same logic as division of labor in our human society. Some cells develop into heart, and some become brain, some become kidneys, some develop into skin. I can't believe my eyes, every cell in my body from the same template, and they have exactly the same DNA, but they become very different organs with very different functions. Apparently cells in a different location synthesize proteins using different DNA fragment, and we can regard the cells differentiation as a kind of Division of labor in cells level. Why is that? I think this division of labor was spontaneous to build up, because all the cells share the same one survival machine, and they must find a way to built survival machine better for themselves to live in, division of labor and cooperation is the good idea, every cell does his job, and then shares all results together, so "cells tissues → organs → systems individual", a perfect division of labor established in basic level.

1.2 Inside the cell
Don’t think that division of labor occurs only at the cellular level, but also much more in micro. Let look at the unicellular organism. A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, unlike a multicellular organism that consists of multiple cells. Historically the simple single celled organisms have sometimes been referred to as monads. The main groups of unicellular organisms are bacteria, archaea, protozoa, unicellular algae and unicellular fungi. Unicellular organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Unicellular organisms are believed to be the oldest form of life, possibly existing 3.8 billion years ago.

A prokaryotic cell has five essential structural components: a nucleoid (DNA), ribosomes, cell membrane, cell wall, and some sort of surface layer, which may or may not be an inherent part of the wall. Bacteria are typical single-celled organisms with a circular DNA molecule and no organelles, and accurately speaking, only one organelle – ribosome, but no other organelles. Here is bacterial cell structure: 

Bacteria, we can regard them as the most primitive life forms, despite their simplicity, contain a well-developed cell structure which is responsible for many of their unique biological properties: cell wall provides the cell with structural support and protection, flagellum's main function is locomotion, pilus sometimes is for the exchange of genes via the formation of 'mating pairs', ribosomes are called as protein factories. What is this? This is definitely a kind of division of labor inside a cell. In eukaryotes, organelles are more detailed in division of labor: some organelle is responsible for manufacturing proteins, some for producing energy, some for transport. For example, mitochondria are the powerhouse of the cell, and it turns out that mitochondria have their own DNA. Scientist named Lynn Margulis in University of Massachusetts, thirty years ago, noted that this business of mitochondria having their own DNA, and came up with this hypothesis that mitochondria used to be independent organisms, that is some symbiotic whatever billions of years ago got into cells that have no mitochondria at that time, and that there have been a symbiosis ever since. Apparently, I support the endosymbiosis hypothesis, because it is consistent with spirit of Division of labor and cooperation in human society. In fact, I think ribosome is the most important organelle and the biggest difference between the bacteria and viruses is that the bacteria have ribosomes, and they can manufacture survival machines to live in by themselves, and we all know survival machines are made by proteins, but viruses don’t have ribosome, so they can't manufacture any survival machines to live in, and the only choice is parasitism not symbiosis. We can regard that emergence of the ribosome is very important division of labor in evolution of life. Compared to a person, if we can call hand, skin, heart and kidney etc as organs, following the same logic, compared to a cell, we also can call pilus, flagellum, cell wall ect as organ(elle)s. These organ(elle)s with very different functions are spontaneous to build up for sharing the common interests. Here I have a question: how did first amino acids come from? Dawkins believes the initial amino acid also generated spontaneously in 'primeval soup', I really don't know.

When a single cell can't be unable to satisfy own needs for its survival (maybe there are too many genes needed to be translated into protein), it and its daughter cells gather together and discuss how to deal it (of course it happened after emergence of mitosis, and I will talk about it later in reproduction methods), based on self-interest, finally they decided to have cells differentiation, a kind of the division of labor in cell level. Eventually they reach an agreement that every cell is only responsible for a part of the DNA translation work into proteins, and all cells share all payoffs together. At this time, organs showed up.

1.3 In genes level
Have you ever thought why lives on earth are so varied and different, but the DNA in all life bodies shares the same monomers-deoxyribonucleotides (nucleotides)? Each deoxyribonucleotide comprises three parts: a nitrogenous base, a deoxyribose sugar, and one phosphate group, and there are four nitrogenous bases in DNA: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). We can regard the sequences of bases in the coding strand of DNA or in messenger RNA as coded instructions for building protein chains out of amino acids. The production of the protein chains is essentially a translation from one code (nucleotide sequence) to another code (amino acid sequence). There are 20 amino acids used in making proteins, but only four different bases to be used to code for them.

All survival machines are with same 4 monomers and same 20 amino acids, but why they are so different? I do believe the key problem depends on the sequence of bases in DNA. DNA nucleotide sequence determines the sequence of amino acid in protein, but because of the difference of permutations and combinations, the traits shows in very different ways with very different functions. I think DNA sequence of eye'synthesis is very different from DNA sequence of kidney on human body, and even though the same organ with similar function, there must be a little difference between two species, for example, DNA sequence of eye'synthesis on cat is not exactly as same as its on human, because cats have excellent night vision, but human don't. Following the same logic, I do believe the DNA sequences of testis are not exactly same between different species (Please remember this point, because I will do some testis gene exchange experiments later). Fundamentally, the division of labor during different organs is derived from the division of labor during different DNA sequences. This is division of labor and cooperation in gene level based on symbiosis. What amazing! It's a bit like music, although there are only seven notes: do er mi fa so la si, but they can be composed into so many different songs due to different permutations and combinations, even if slightly changed a few notes, you could feel the differences. Evolution of life is more wonderful, because there are only four notes, God can write variety of creatures, we human should hold the power of nature in awe and veneration.

2 Binary fission → Mitosis → Meiosis
2.1 Binary fission
Binary fission is a form of asexual reproduction and cell division used by all prokaryotes, (bacteria and archaebacteria), and some organelles within eukaryotic organisms (eg, mitochondria). Most bacteria rely on binary fission for propagation, and in binary fission, two daughter cells are produced by a single parent cell which effectively clones itself and the cell starts by duplicating its DNA to create two complete sets, and then growing to a size much larger than it usually is. As the cell grows, the sets of DNA move to opposite ends of the cell. Once the cell has achieved the right size, it splits in two, creating two daughter cells with identical DNA. 

Notice here: most prokaryotes have a genome that consists of a single DNA molecule, whereas most eukaryotes have much more than one DNA molecule. Why is that? I think that is the reason why prokaryotes only can retain binary fission, but eukaryotes can be evolved into mitosis phase. I try to give you my interpretation.

When a cell only has one DNA molecule, after replication a cell splits in two parts, and the each daughter DNA molecule must occupy one cell singly as possible. I think it is not hard to understand, according to Hund's Rule, if two or more orbitals of equal energy are available, electrons will occupy them singly before filling them in pairs. These two are in same logic, so the binary fission works fine in a cell which only has one DNA molecule inside.

What about a cell which has two DNA molecules before split? It means there are 4 DNA molecules in one cell after DNA replication and before cell splits. How to allocate these 4 DNA molecules into two cells is a very important step in reproduction process, because it involves precise replication problem and the stability of offspring. For example, there are A and B DNA molecules in a cell, and A replicate A1, B replicate B1, which match which if under random distribution, maybe A and A1 go the a same one daughter cell, and B and B1 are together, and the result is one daughter cell has two sets of eyes genes without any set of kidney genes, and the other has two sets of kidney genes without any set of eyes genes. Binary fission must provoke confusion. How to solve this problem – Mitosis? 

2.2 Mitosis:
Mitosis occurs only in eukaryotic cells, of course after the evolution from prokaryotes to eukaryotes. Compared with binary fission in prokaryotes, I do believe that the biggest advantage of mitosis is not only accurate replication, but also accurate distribution. Frankly speaking, I don't think the DNA replication in binary fission is not precise, because according to Dawkins 'survival of the stable', if binary fission can't accurately replicate DNA, the species can not be stable. So I think the emergence of mitosis is to solve distribution problems, and is the premise of cell differentiation.

You may ask me“why and how one DNA molecule became two DNA molecules in a cell, if you say the emergence of multiple DNA molecules is before emergence of mitosis.” Very good question, do you remember I mentioned pilus in bacterial introduction sometimes is for the exchange of genes via the formation of "mating pairs"? In addition to reproducing via binary fission, many prokaryotes can also reproduce sexually – a specific sexual reproduction. Sexual reproduction is important, because it contributes to genetic diversity by blending the genes of various individuals. Repeated sessions of binary fission would reduce genetic diversity, making the species as a whole very susceptible to being wiped out. Sexual reproduction mixes things up, keeping the species diverse and promoting the development of beneficial mutations. Conjugative pili play a very important role in this kind of sexual reproduction. I do believe this is the most important and most direct channel for a cell to complete the primitive accumulation in number of DNA molecules. 

When there are more than two DNA molecules in a cell before replication, they have to solve the problem how to make sure two exactly same daughter DNA molecules not go to the same one daughter cell, and then the centromere and spindle fibers showed up in evolutionary history. We can say that the emergence of spindle fibers point out the direction for the separated sister chromatids by the attraction to the centromere, and I think the mitosis is the best way to solve this problem. My theory of evolution is unicellular organism with one DNA molecule first, and then multiple DNA molecules with mitosis in one cell, and then cells accumulation and differentiation. Apparently, mitosis is the premise of multi-cellular organism, because multi-cellular organisms must cause the division of labor and cooperation in cell level and needs very accurate replication and accurate distribution as premise, in order to ensure that each every cell has all genes required for protein in different organs.

Emergence of Diploid
After solve distribution problem by mitosis, so far the organisms are still in haploid era, until one day a serious mistake happened during the process of mitosis: Chromosome replication and centromere separation are both successful, but the mother cell do not split into two. Now another important node in evolution first showed up in history: Diploid. The significance of diploid is very substantial: first of all, provide a whole set of backup genes in case of lethal mutations, and organisms would be more stable; secondly the alleles on homologous chromosomes began to mutate independently, and that is the key of biodiversity in the same species; finally diploid provided the possibility of meiosis and sexual reproduction, so emergence of diploid is the most important node in evolution. I think that is why most eukaryotic species have evolved into diploid era. Key words: possibility, emergence of diploid is a necessary condition for meiosis and sexual reproduction, but not a sufficient condition. The facts prove that so far there are still some diploid organisms in asexual reproduction era.

2.3 Meiosis
After Mitosis, it is time for Meiosis to show up. Obviously, the Meiosis must inevitably happen after appearance of diploid. Sexual reproduction occurs only in eukaryotes, during the formation of gametes, the number of chromosomes is reduced by half, and returned to the full amount when the two gametes fuse during fertilization, but so far, many eukaryotes species are still stuck in the asexual reproduction stage, especially lots of plants. In other words, some plants have evolved to the phase of mitosis, multicellular and diploid, but they still have not evolved an organ which can produce meiosis; some plants are sexual reproduction but dioecious; some plants are sexual reproduction but monoecious, and dioecious plants can be divided into unisexual and bisexual flowers. If we can believe our human are at the end of sexes differentiation, we can also consider that the plants distribute at the beginning, middle and end of sex evolution. Why? We can do some deep research here now, and then compare with some phenomena in animals.

3 Asexual reproduction → sexual reproduction.
Here I want to illustrate my views by chronological order. There is no doubt that mitosis definitely is a kind of asexual reproduction, and at the beginning, we can regard mitosis as a sole reproductive strategy, until a dedicated organ, only for reproduction, was differentiated, because of further division of labor in organs level.
3.1 Sporogony
Sporogony is a type of sexual and asexual reproduction. I think the emergence of sporangium means the plants started to evolve a specialized organ which specifically for reproduction, whatever asexual or sexual spores. Organs of plants can be divided into vegetative and reproductive, and before sporogony, plants use vegetative organs to create the new generation of plants, like roots, stems, and leaves;After specialized organ shows up, the vegetative organs don't take the responsibility for reproduction, and we can consider the specialized sex organ as the result of detailed division of labor. I do believe that asexual spore is a presage of meiosis, and initially it must be mitosis plus asexual reproduction.

3.2 Meiosis
There is no meiosis in sporangium at the beginning; it is just the result of organ differentiation and they are still in the phase of asexual reproduction. As time goes by, the accident happened, specifically speaking, for some reasons, disorder of mitosis in sporangium happened. I think it is not hard to understand, we can regard the meiosis as two consecutive mitoses: meiosis I is an abnormal mitosis, and meiosis II is a complete mitosis. If we can say emergence of sporangium is the result of detailed division of labor in organs, then we can identify meiosis as evolution inside this organ.

About meiosis I, we can regard it as the separation of homologous chromosomes, and about meiosis II, we can identify it as the separation of sister chromatids. This is the core idea of Meiosis. Next, please follow me to try reverse thinking in the process of Meiosis, and maybe we can get something new we ignored before. I think the reverse process of meiosis is the evolutionary history of organisms, and I can roughly draw out the path.

First of all, unicellular organisms showed up in the evolutionary history of organisms, but with the number rise of DNA molecules, evolution need to find a way to solve the problem of distribution, so evolution find a way called mitosis, and centromere and sister chromatids showed up in history. Either live or die, the most brutal rule of the evolution game, yeah? Secondly, due to some unknown reason in the process of mitosis, accident happened again that centromere separation succeeded, but cell division failed, therefore the prototype of homologous chromosomes and diploid organisms showed up in the evolutionary history for the first time. Perhaps you will say this assumption is too far-fetched, but I do believe the evolutionary history of organisms is also composed by a series of accidents as same as human history, and in fact, our every each person is the result of accident, if my mother and my father didn't mate that night, I am not who I am now right? Since then the alleles from two homologous chromosomes started mutation independently on diploid organisms, there are not only 2 kinds of alleles in a diploid species, for example the alleles which control the color of human hair have more than 2 kinds, black, yellow, red, brown, and human eye color also followed the same logic, amber, blue, brown, bray, green, hazel. These organs between different races don't share the exactly the same genes, but with the same functions, so I presume genitals genes are not identical between different races, but also with same function. And then in translation into protein game, any one pair of alleles has the rules in the same environment (external environment mainly refers temperature, plus the gene-environment mainly refers positive or negative effect), and this is called dominant, recessive and co-dominant genes proposed by Gregor Johann Mendel. In fact, the dominant gene and recessive genes are not absolute, but relative, for classic example, apparently the testis genes is dominant in mammals, but ovarian genes is dominant in birds, so this leads to relative dominant one start to dump needless genes. With the gender differentiation, mammals become XX/XY, and birds become ZZ/ZW, but the only common they share is the chromosome with the dominant genes become shorter. I do believe all things are interlinked.

3.3 Parthenogenesis
I guess parthenogenesis was the first stage after meiosis emergence. In biology, now we usually define it as a form of reproduction in which the ovum develops into a new individual without fertilization. This is called apomictic parthenogenesis. We use“ovum”as the start of the apomictic parthenogenesis, but I believe, at the beginning of the parthenogenesis, there is no“ovum”or concept of male and female differentiation at all, because at that time there is no division of labor in gametes yet, so we’d better define parthenogenesis as gamete develops into new individual without fertilization.

After meiosis appeared, there is no sexual differentiation immediately, so at this time haploid individuals appeared again, because diploid is not necessary condition for mitosis, as long as a haploid carry a complete set of genes, it can develop into a new individual, and homologous chromosomes in diploid only plays the role as backup. I think the reason why diploid is much more common in the world than haploid, triploid, tetraploid or hexaploid, is the result of balancing the interests between costs and benefits. So far, there are still many organisms which keep the characteristics of apomictic parthenogenesis, a typical example is bees: The queen and worker bees are both the product of a fertilized egg, but drones are the product of an unfertilized egg. 

Studies have shown that haploid individuals, however, are usually non-viable, and parthenogenetic offspring usually have the diploid chromosome number. In my opinion, the reason why lots of haploid individuals are non-viable is there is only one set of genes in haploid no backup, so once a useful gene has a mutation, it will be a fatal disaster in the development of haploid. Here is same logic example: Hemophilia. Every one knows hemophilia is more common in males than females, because Hemophilia is caused by a recessive allele on the X chromosome. (The subtext is that the hemophilia genes have already been abandoned on Y chromosome.) This disease has fully exposed the fatal flaw of haploid, and that is why evolution prefers diploid better. The more advanced organisms evolved, the harder parthenogenesis happened, so phenomenon of parthenogenesis occurs much more common in lower organisms than higher organisms. The facts prove that so far parthenogenesis occurs naturally in many plants, some invertebrate animal species (including nematodes, water fleas, some scorpions, aphids, some bees, some Phasmida and parasitic wasps) and a few vertebrates (such as some fish, amphibians, reptiles and very rarely birds).

I think there are two reasons why higher organisms, especially higher vertebrates, chose to give up on Parthenogenesis: first of all, with increase in the number of genes and further detailed division in organs, whether survival or not depends on mutual cooperation of all organs, once an organ has a fatal flaw because of bad mutated genes, it will bring disastrous result to the haploid individual, so the more higher organisms, the more they need second whole set of genes as backup; secondly, the mating between female and male become much easier after evolution from TSD to GSD, and initially because of sex determination by temperature, there would be a group all male or female. For example, in TSD model, due to the extreme weather, maybe all eggs hatch into females or males, maybe a female can't meet a male in her whole life, but after organisms evolution into sex determination by genes, organisms have already got rid of the control from the outside on sex ratio, and sex ratio approximately remains at 1:1, and the probability that a female meets a male increased. So female don't have to choose parthenogenesis as her reproduction strategy, now she can give it up on parthenogenesis step by step. Frankly speaking, the sex ratio of 1:1 is determined by two sex chromosomes, but it is not a perfect ratio, because of the different division in reproduction between female and male, it must require much more female than male, so mostly of male don't have the chance to mate for the whole lives, but they don't hesitate to eat all food as they can.

3.4 Self-fertilization
Self-fertilization requires only one organism, and I guess this was the second stage after meiosis emergence. Self-fertilization (also known as autogamy) occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual. Key words:“hermaphrodite”, I do believe that at the beginning of self-fertilization, there is no hermaphrodite or concept of male and female differentiation at all, because at that time there is no division of labor in gametes yet, or we can say that there is only one gender, neither male nor female, because primitive gonad didn't have mutation yet.

I believe that evolution history is as same as human social progress with some twists and turns. When meiosis occurs unexpectedly for the first time, organisms indeed go back to haploid era, but life always finds a way because it has tasted the benefit of diploid – more stable, according to the principle of“survival of the stable”, so life need to find a way to get back to diploid ear - gametes fusion is good idea I think. Two gametes from the same individual fusion together appeared first, because at this time, evolution did not even think the issue of biodiversity, the only problem it wanted to solve was stability, so clones or semi-clones occurred for the first time. I do think self-fertilization is another important node, it indicates the direction in the process of evolution. After the satisfaction of stability, life stumbled across another advantage of gametes fusion: diversity, even though offspring of self-fertilization are the slight variation replicator, but under the“huge-crowd strategy”strategy, it indeed increases the adaptability of the species to the environment. So now evolution chose this strategy as a mainstream reproduction that meiosis first, then fusion, and we can regard the self-fertilization as embryonic form of Lottery Principle.

Here I want to explain the term“huge-crowd strategy”for a little bit. The term “huge-crowd strategy”I used is consistent with the term“Lottery principle”like the term“Human wave tactics”or the term“Elitism”I think, but I am not sure the meaning I understand is the real meaning or not in English. I will write about my opinion about these terms later after I finish reading the“In Defense of Elitism”.

So far, still many organisms retain the shadow of self-fertilization, including most flowering plants, numerous protozoans, and many invertebrates. Autogamy, sometimes referred to as self-pollination, the production of gametes by the division of a single parent cell, is frequently found in unicellular organisms such as the protozoan Paramecium. These organisms, however, may also reproduce by means of conjugation, in which cross-fertilization is achieved by the exchange of genetic material across a cytoplasmic bridge between two individuals. Likewise, among higher plants, most of which are monoecious (i.e., bisexual—male and female gametes being produced by the same individual), most self-pollinating species are also capable of cross-fertilization, and even those that are obligate self-fertilizers are occasionally cross-pollinated by accident. Hermaphroditic animals (those in which both male and female gonads are borne on one individual) are rarely capable of self-fertilization, since many such species have adaptations encouraging cross-fertilization. There are two types of self-pollination: In Type I self-pollination, pollen is transferred from the anther to the stigma of the same flower. Such flowers are hermaphrodites, which have both sexes. In Type II pollen is transferred from the anther of one flower to the stigma of another flower from the same plant. Every coin has two sides. There are several advantages for self-pollinating flowers. If a given genotype is well-suited for an environment, self-pollination helps to keep this trait stable in the species. Not being dependent on pollinating agents allows self-pollination to occur when bees and wind are nowhere to be found. The disadvantages of self-pollination come from a lack of variation that allows no adaptation to the changing environment or potential pathogen attack. Self-pollination can lead to inbreeding depression, or the reduced health of the species, due to the breeding of related specimens. This is why many flowers that could potentially self-pollinate have a built-in mechanism to avoid it, or make it second choice at best. Genetic defects in self-pollinating plants cannot be eliminated by genetic recombination and offspring can only avoid inheriting the deleterious attributes through a chance mutation arising in a gamete.

Both the advantages and disadvantages remind me of one concept: incest. Incest is sexual activity between family members and close relatives. Different cultures have different views about incest, However, sexual relations with a first-degree relative (such as a parent or sibling) who share 50% DNA, is almost universally forbidden. In some societies, such as those of Ancient Egypt and others, brother–sister, father–daughter, and mother–son, cousin-cousin, aunt-nephew, uncle-niece, and other combinations of relations were practiced among royalty as a means of perpetuating the royal lineage. In my opinion, incest is not so horrible, it is just a typical self-fertilization, and it has all characteristics of self-fertilization, both advantages and disadvantages. I understand why inbreeding always happened in Royalty and Nobility, because they wanted to keep the bloodlines pure, and self-fertilization is good idea to keep that. Apparently, there is no concept of incest in non-human animals, why? Because incest is named only by our human. People tend to avoid close inbreeding, and this starting point is not wrong, but only under the consideration of genes defects, not feelings. The reason why incest is forbidden in many cultures is that our human haven't separated sex from reproduction yet. This is all evolutional faults that our human reproduction was kidnapped by male orgasm. What if a pair of brother–sister separated from each other in their childhood, and they don't know the blood relationship at all, but they are in love with each other, should they get into marriage? From a much more macro perspective, the two people from the same race can't get into a marriage, because this is a kind of Self-fertilization, and Anglo-saxon cant marry another Anglo-saxon, he or she only should marry a black one or yellow one. Do you agree with that? Today our slogan is Liberty, Equality, Democracy and Fraternity, and I believe one day our offspring will face this issue better. By the way, I think there is no age disparity problem in a relationship, because we are all survival machines as a kind of loose-leaf binders of human genes, only someone synthesized early, and someone synthesized later. Essentially I am my mother's daughter is equal to my mother is my daughter in genes, we just share the same half genes. This point is very clear in“The selfish gene” by Richard Dawkins. I do believe marriage only should observe two basic principles: one is adult, the other is voluntary.

After back to the diploid with method of self-fertilization in order to be more stable, evolution unexpectedly discovered the benefits of biodiversity, even if only a little bit different, because alleles from two homologous chromosomes have already started mutation independently on diploid organisms. Now evolution intended to start the Lottery Principle, because of cruel huge-crowd strategy, as long as one combination can survive. Frankly speaking, our human history is also a continuation of cruel huge-crowd strategy not in genes, but in thinking. Evolution of genes is as same as Memes spreading, either a gene mutation or truth emergence must started from one individual, and then spread out. Human history is always changed by the few, because the truth is always in the hands of them. People in 15th century never understood that the Earth is not the center of the universe, but it doesn't matter, because they have to face the death, and follow same logic, people today maybe never know the truth of female orgasm, but it also doesn't matter, I write all these for offspring to read.

3.5 Isogamy
There is still no sexual differentiation in Isogamy era. Isogamy is a form of sexual reproduction that involves gametes of similar morphology (similar shape and size), differing only in allele expression in one or more mating-type regions. Because both gametes look alike, they cannot be classified as "male" or "female." Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "-" strains, although in some species there are more than two mating types (designated by numbers or letters). Fertilization occurs when gametes of two different mating types fuse to form a zygote.

Frankly speaking, I don't think evolution has the foresight, and we can regard isogamy as an extension of self-fertilization. If we identify the purpose of self-fertilization is for going back to more stable diploid, and apparently the purpose of Isogamy during two gametes is for Lottery Principle. Of course, at the beginning it must happen accidentally, and evolution found diversity is indeed helpful for adapting to different environment. In order to increase diversity, the first thing evolution has to do is to prevent self-fertilization, so evolved two mechanisms: one is Self-incompatibility, the other is Dichogamy. So far, our human beings, as the most evolved creatures on the planet, still keeps these two characteristics. I think self-incompatibility is the reason why my polar body and my egg can't fuse together, and dichogamy is the reason why on the average, girls reach puberty about 2 years earlier than boys in human beings. I think it is not hard to understand, and you can imagine that a female mouse can give birth to about 6 babies at one time, the sex ratio basically 1:1, if the 6 baby mice reach puberty at the same time, and the maximum possibility is mating between brother and sister, a kind of self-fertilization. Our human just evolved from multiple births to single birth, but we still have the characteristic of dichogamy. Even in bisexual flowers of plants, there are also two cases: adichogamous flower and dichogamous flower. These facts all illustrate that evolution indeed prefer the gene mixed to adapt the external complex environment. By the way, Isogamy is a real kind of homosexuality, because there is only neuter at that time.

3.6 Anisogamy
Anisogamy is viewed as the primary sexual differentiation. It (also called heterogamy) refers to a form of sexual reproduction involving the union or fusion of two dissimilar gametes (differing either in size alone or in size and form). The smaller gamete is considered to be male (sperm cell), whereas the larger gamete is regarded as female (egg cell). Frankly speaking I don't know whether the theory of sperm competition by Geoff Parker is right or not, but I believe that the origin of anisogamy must be related to alleles'mutation of sex organs; I don't know sperm is selfish or not, but I believe that we can view the anisogamy just as a result of division of labor in reproductive strategy.

As I said before, alleles started mutation independently on homologous chromosomes after entering the diploid era, and when evolved into the Isogamy era, the alleles which control the sex organs did not mutate yet, and the two gametes have the same size, same nutrients, and same swimming capability, there is no doubt that, as same as the advantages of the division in human society, Isogamy strategy must lead to inefficiency, until one day sex genes mutated, according to Adam Smith, the division of labor is spontaneous, and then sexual differentiation first formal on stage of history. Due to the different roles of the division and coevolution, two different sex genes lead neutral gametes go to opposite directions.

Here I want to make an explanation of coevolution. The term coevolution is used to describe cases where two (or more) species reciprocally affect each other's evolution. For example, an evolutionary change in the morphology of a plant, might affect the morphology of an herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore...and so on. Key words: two (or more) species, we generally regard coevolution between two different species, and coevolution of different species includes the evolution of a host species and its parasites (host–parasite coevolution), and examples of mutualism evolving through time, but I think coevolution also happens in gamete differentiation. This process can be called as a process of “as one falls, another rises.”, and I really don't know why ovarian genes chose to become big with rich nutrients, and testis genes chose to become small with good mobility, but I think the reason must be related to their own talent. It is not hard to find that women find it easier to gain weight than men and men have more talent in sports than women generally speaking. Apparently, estrogen synthesized by the ovaries determines female are more inclined to carry nutrients, and androgens synthesized by the testis determines male are more inclined to move. Shaun White with 170cm height can do double McTwist 1260, but no women can do that, even also with 170cm height. As a woman, I have to admit male physical quality is indeed better than female, but this difference is just because every organ is affected by different hormonal environment, don't make it cover the human nature please.

Coevolution not only happened in biological evolution, but also in human social evolution, and even the relationship between the sexes is also the result of coevolution. We can hypothesize that people from different countries are different species in the evolution. The way how men treat women is the result how women treat themselves, I do believe one day when women really wake up from Utopia of female orgasm, men will accept the reality and have a conversation on equal terms with women, because they don't have another option, and this is definitely a kind of co-evolutionary process. This theory of coevolution still works in democratic process, the reason why Kim fat can swagger is North Koreans are stupid. Never forget ignorance is the only soil to produce authoritarian, whatever in sexual autocracy or political autocracy. The dictators always build various doctrine or theory to brainwash the victims, and let them give up the most basic human rights. We must wake up as soon as possible.

Do you remember the testis genes exchange experiment what I said before? Here I am going to do exchange experiments, and finally give the results to Freud and someone who believe in penis envy like him. 1, We can pick out two sperm: one is from male dog with Y chromosome, the other is from male bird with Z chromosome, and then adopt gene technology to exchange the testis genes between them, and then make them fertilize the eggs respectively. Do you think the baby male dog will lose the penis, because male birds don't have penis? Do you think the baby female bird or male bird will have the penis, because dog have penis? 2, We can also pick out two sperm: one is from male dog with X chromosome, the other is from male bird with Z chromosome, and then adopt gene technology to exchange the ovarian genes and testis genes between them, and then make them fertilize the eggs respectively. Do you think the baby female dog will have a penis, or still clitoris shaft, or cloaca? Do you think the baby female bird or male bird will have clitoris shaft or cloaca? 3, what if we inject the testosterone to a mammalian zygote with XX chromosomes from the beginning of fertilization, do you think she will have penis? Here I give you my speculation: in experiment 1, the baby dog still have penis, and baby bird whatever female or male don't have penis at all; in experiment 2, the baby female dog will have penis, even though she still have XX chromosomes, and baby bird still have cloaca; in experiment 3, this is the process of female potted hyena. Next, the key question is what revelation we can get from these experiments: the vulva morphology not only depends on the hormonal environment, but also on other accessory sex gland gene carried by which species. Honestly, the hormonal environment controlled by primary sex gland like ovary or testis doesn't play a decisive role, but what kinds of genes on X chromosome is the key of the reproduction strategies, and we can conclude that the genes which control the synthesis of male secondary sex organs, like ducts, glands and the penis, are all on X chromosome, but why women can't have the real orgasm as male? Women are not “the other” in“The Second Sex”by Simone de Beauvoir, but also the subject and the absolute as same as men.

Do you find a very interesting phenomenon? As we all know, male always take the initiative in courtship in almost all animal species, not only in human beings, but why? Maybe you will say male enjoys the sex more than female, because men always orgasm in sex, but women can't. I will answer“No”. Because this interesting phenomenon not only happens in mammals, but also in reptiles, amphibians, fish, insects and arachnids, and they adopt“cloacal kiss”or“in vitro fertilisation”to reproduce, and they don't even have penis at all. I believe this phenomenon occurred after the sexual differentiation. Before sexual differentiation, organisms chose self-fertilization or isogamy as the main reproductive strategy, but after division of labor appeared spontaneously, the original pattern was broken. So what exactly does the term “sexual differentiation” mean? In my opinion, it means a kind of division of labor in two kinds of gametes, and one gamete goes to one direction of becoming big with rich nutrients but illiquidity, and the other gamete goes to the opposite direction of becoming small without any nutrients but good mobility. Apparently, the purpose is in order to increase productivity, division means male gametes have to make a compromise and lose a very important condition - Nutrients necessary for growth, but please don't forget organisms are evolved from parthenogenesis and self-fertilization era, it must lead to an inevitable consequence - Asymmetric Dependence. Sperm, as a party in a weak position, can't spread the genes by themselves, and they don't have an option except fertilize a nutrient-rich egg, so whatever in which species, male always takes the initiative in courtship. On the contrary, female gametes with rich nutrients are in strong position, and even though they can' mate a male all the time, they can use parthenogenesis or self-fertilization to reproduce, I admit this is just second best thing for female, but anything is better than nothing, right? I believe that Asymmetric Dependence between male and female gametes is the reason why male always take the initiative in courtship in almost all animal species. On this point, I believe Richard Dawkins and I share the same view, but he didn't clarify from an evolutionary perspective. He wrote “She has a strong card in her hand. She can refuse to copulate. She is in demand, in a seller's market. This is because she brings the dowry of a large, nutritious egg. A male who successfully copulates gains a valuable food reserve for his offspring. The female is potentially in a position to drive a hard bargain before she copulates. Once she has copulated she has played her ace—her egg has been committed to the male. It is all very well to talk about driving hard bargains, but we know very well it is not really like that. Is there any realistic way in which something equivalent to driving a hard bargain could evolve by natural selection? I shall consider two main possibilities, called the domestic-bliss strategy, and the he-man strategy.” The term - Asymmetric Dependence also appeared in human society, if you know some Chinese history, it is not hard for you to understand the term “Asymmetric Dependence”. The reason why Mao chose the strategy of “Encircling the Cities from the Rural Areas” is that, at that time in China, city can't live without rural areas, but rural areas can live without city.

In Chapter“Battle of the sexes”, Dawkins also has a doubt about another strange phenomenon. “One feature of our own society that seems decidedly anomalous is the matter of sexual advertisement. As we have seen, it is strongly to be expected on evolutionary grounds that, where the sexes differ, it should be the males that advertise and the females that are drab. Modern western man is undoubtedly exceptional in this respect. It is of course true that some men dress flamboyantly and some women dress drably but, on average, there can be no doubt that in our society the equivalent of the peacock's tail is exhibited by the female, not by the male. Women paint their faces and glue on false eyelashes. Apart from special cases, like actors, men do not. Faced with these facts, a biologist would be forced to suspect that he was looking at a society in which females compete for males, rather than vice versa. In the case of birds of paradise, we decided that females are drab because they do not need to compete for males. Males are bright and ostentatious because females are in demand and can afford to be choosy. The reason female birds of paradise are in demand is that eggs are a more scarce resource than sperms. What has happened in modern western man? Has the male really become the sought-after sex, the one that is in demand, the sex that can afford to be choosy? If so, why?” I will try to give my detailed answer to Dawkins in future. In short, men have already evolved out of the reproductive cycle, but women haven't.

4 Sex-determination system and Evolution from Cold-blooded to Warm-blooded
4.1 Sex-determination system
Most sexual organisms have two sexes. In many species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology, and we call it as genotypic sex-determination (GSD); in other cases, sex is determined by environmental variables (such as temperature) or social variables (eg the size of an organism relative to other members of its population), and we call it as temperature-dependent sex determination (TSD). Mammals and birds only have GSD, whereas crocodilians and sphenodontians exclusively have TSD. In contrast, squamates (lizards and snakes) and turtles exhibit both GSD and TSD, although the latter is much more common in turtles than in squamates. The key words: different alleles. In my theory, as long as we talk about alleles, we must involve dominant gene, recessive gene and co-dominant, and I believe these three types of relationships are the keys to sexual differentiation. In my view, sexual differentiation is just a kind of division of labor as a reproductive strategy in cruel evolutionary process, and by the same token, it must share the both advantages and disadvantages of division of labor like in human society.

4.2 Cold-blooded and warm-blooded animals
The term warm-blooded is a colloquial term to describe animal species that have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes. A large proportion of the creatures traditionally called "warm-blooded", with a few exceptions, all mammals and birds are warm-blooded, which means that they can make their own body heat even when it is cold outside. Whether it is sunny and hot outside or there is a snowstorm and it is very cold, warm-blooded animals have body temperatures that usually stay the same.

A cold blooded animal, or ectotherm, is one that does not have an internal mechanism for regulating its body temperature. Instead, a cold blooded animal relies on solar energy captured by the environment. Cold-blooded animals, like reptiles, insects, arachnids, amphibians, and fish, become hotter and colder, depending on the temperature outside. For example, when the sun sets at night, their bodies are cooler because it is less warm outside. When the sun is out, however, their bodies soak up the heat and become warmer.

4.3 Coincidence?
Have you noticed an interesting and coincident thing? Basically, just only birds and mammals are not only warm-blooded animals, but also GSD. Moreover, ovarian genes are dominant genes in birds, and testis genes are dominant genes in mammals. It is just 50-50. Why is that? Is this really a coincidence? Frankly speaking, I don't think so; there must be some relationship between them. I think if we want to figure out the mystery of sexual differentiation, we must start with the evolution from cold-blooded to warm-blooded. Look at the birds and mammals, they are both warm-blooded animals, but they share different body temperature. Most mammals have a typical body temperature of about 37 degrees C, and birds have a typical body temperature of about 41 degrees C. I believe that the two different body temperatures are the reason why ovarian genes are dominant in birds and testis genes are dominant in mammals.

Let’s go back to an earlier question why animals would evolve into warm-blooded from cold-blooded. Personally, I think the fundamental driving force is more stable and getting rid of the influence of the external vagaries environment. Actually Dawkins has given the answer: Survival of the stable. Apparently, a constant and proper temperature is very beneficial for survival machines, whatever in protein synthesis, enzyme property, brain development or nerve conduction. Common examples: when food is cooked, some of its proteins become denatured, and this is why boiled eggs become hard and cooked meat becomes firm. There is no doubt that specific heat capacity of water has a very high specific heat capacity: 4.184kJ/(kg•K) - the second highest among all the heteroatomic species (after ammonia ), as well as a high heat of vaporization, so we can roughly consider water temperature is basically unchanged, and especially in deep sea, the ambient temperature is almost constant. I think that is the reason why mostly cold-blooded animals can’t leave water, because they have to use water to keep the relative balance of body temperature, and that is why some studies have already shown that the time spot when some animals evolved from aquatic to terrestrial coincided with the time when they can maintain a constant body temperature. Just due to the thermostat system, as diploid organisms, animals can get the decision-making power of sex-determination back to their own genes from the clutches of ambient temperature. In my opinion, the reason why birds and mammals chose different body temperature is the result of mutual compromise during all organs and systems, and I am convinced that dominant genes and recessive genes are relative, and in birds body of 41 degrees C, ovarian genes are dominant; on the contrary, in mammals body of 37 degrees C, testis genes are dominant. In fact, we can regard the GSD as an extension of TSD, just under constant temperature.

There is no doubt that earth life originated at sea, and they used IVF as reproduction strategy, because water is a good medium. After the pulmonary respiration evolution, they began to come ashore, but they were still in the cold-blooded era, so they had to use water to keep the balance of body's temperature, until they evolved into warm-blooded era, and then they thoroughly can get rid of the sea. Every coin has two sides. They lost a best medium for sexual reproduction, so they had to choose in vivo fertilization as reproduction strategy.

Maybe you will say it is just my subjective assumption. Here I give you another interesting and intriguing example. So far the accurate mechanism of TSD is currently not well understood, but two distinct patterns have been discovered and named Pattern I and Pattern II by Michaela Ewert, with Pattern I further divided into IA and IB. Pattern IA has a single transition zone, where eggs predominantly hatch males if incubated below this temperature zone, and predominantly hatch females if incubated above it. Pattern IB also has a single transition zone, but females are produced below it and males above it. Pattern II has two transition zones, with males dominating at intermediate temperatures and females dominating at both extremes. Very near or at the pivotal temperature of sex determination, mixed sex ratios and, more rarely, intersex individuals are produced. Key words:“predominantly”, it means even in males temperature zone there are still some eggs hatch females, and in female temperature zone there are still some eggs hatch males. Do you feel weird about why always some naughty eggs do not observe the rules?

Here I give you my theory about mechanism of TSD. First I agree to this statement very much that sex chromosomes are derived from a pair of autosomal chromosomes. In my opinion, if we want to figure out the whole story of the sex determination, we must restore them back to the original condition and regard the ovarian genes and testis genes as two common alleles in a common pair of homologous chromosomes. Since they are alleles, they must follow the laws of inheritance about dominant and recessive genes by Mendel. We can imagine that after evolution into diploid era, isogamy dominated the world, until the gene of reproductive organs had a mutation, and then sexual differentiation started to board the stage of history. Under the principle of mutual benefit, ovarian genes chose to become big with rich nutrients, and testis genes chose to become small with good mobility, and as I said before, we can consider this sexual differentiation just as a kind of spontaneous division of labor. Here I mark uppercase letter“A”as testis genes, and lower case letter“a”as ovarian genes, and I need to clarify uppercase letter“A”doesn't mean dominant genes, and lower case letter“a”doesn't mean recessive genes, which one is dominant is relative.

Through Mendel's experiments, we all know genotype and phenotype are not a concept, because we are diploid organisms. When a pair of alleles located on a pair of homologous chromosomes are same, we call it as homozygote, precisely speaking, just homozygote in this alleles, and I believe there is no 100% real homozygote in this world, because we are built by many alleles, unless doubling chromosomes in gametes by colchicine we can get real homozygote; when a pair of alleles are not same, we call it as heterozygote. Now the key of problem is heterozygote or homozygote. Based on only two alleles in genitals genes: one is A, the other is a, there are totally three combinations in genotypes: heterozygote (Aa), homozygote (AA or aa). I do believe the heterozygote (Aa) is the key of TSD, because the sexual morphology of heterozygote (Aa) exhibit either testis or ovary, but the phenotype of AA only exhibit testis and aa only exhibit ovary. Actually this is the heterozygote unique advantage: one more option.

In cold-blooded animals, when incubation temperature in male temperature zone, it means this temperature is more suitable for protein synthesis of testis genes, and testis genes are dominant genes under this environment if the egg is heterozygote, but now homozygote (aa) still exhibit ovary, because it doesn't have testis genes at all. So now the phenotypes exhibit testis, but there are two genotypes: homozygote (AA) and heterozygote (Aa).

Similarly, in cold-blooded animals, when incubation temperature in female temperature zone, it means this temperature is more suitable for protein synthesis of ovary genes, and ovary genes are dominant genes under this environment if the egg is heterozygote, but now homozygote (AA) still exhibit testis, because it doesn't have ovary genes at all. So now the phenotypes exhibit ovary, but there are two genotypes: heterozygote (Aa) and homozygote (aa).

when incubation temperature in transition zone, it means this temperature has no preference, and ovary genes and testis genes have equal opportunity to synthesize, so now homozygote (AA) still exhibit testis, and homozygote (aa) still exhibit ovary, and heterozygote (Aa) enter a game of coin flipping, which is a form of sortition which inherently has only two possible and equally likely outcomes. So if phenotypes exhibit ovary, there are two genotypes: homozygote (aa) and heterozygote (Aa), and if the phenotypes exhibit testis, there are also two genotypes: homozygote (AA) and heterozygote (Aa).

There are four cases when a male and a female mating, and all obey Mendel‘s First Law: Alleles segregate equally. In the F2 generation, 3/16 offspring exhibit male permanently, and 3/16 offspring exhibit female permanently, 10/16 offspring exhibit hermaphrodite. So how should we define the term of “Hermaphrodite”, based on the sexual genotypes, or the phenotypes of the primary sex organs: testis and ovary, or secondary sex organs: layout of vulva? I am really confused by the definition, maybe our human like to classify too much.

Now I can use this theory to explain why there are always some naughty eggs do not obey the rules during opposite temperature zone, I think it is not hard to understand in society, it is like election in Game Theory, the Yale open course. The key of election is to convince the centrist, rather than 100% left-wing or 100% right wing parties, because they only have just two options. I don’t want to just stop, and I am planning to go further from here. What about the sex determination after the evolution into warm-blooded era? There are two cases after entering the warm-blooded era: one is body temperatures prefer testis genes as dominant genes, and the other is body temperatures prefer ovarian genes as dominant genes.

When body temperatures prefer testis genes as dominant genes in warm-blooded animals, at the beginning of the temperature determination, if the phenotypes exhibit male, there are two genotypes: homozygote (AA) and heterozygote (Aa), and then mate with a female one which genotype must be homozygote (aa). Notice here: there is no male with AA genotypes in offspring. What does it mean? I think it means when body constant temperatures were determined and prefer testis genes as dominant genes, the males with AA genotype were eliminated immediately, and there is only one male genotype: Aa, and from now on, heterozygote (Aa) takes the responsibility of being male. Day after day, the sex chromosome which always has the dominant genes started to shake off the Junk genes on itself, until only necessities left. I think this is the formation process of mammalian sex chromosome XX/XY. Don’t worry, because one side is heterozygous diploid, and the other side is homozygous, so the sex ratio quickly returned to 1:1.

Similarly, when body temperatures prefer ovary genes as dominant genes in warm-blooded animals, at the beginning of the temperature determination, if the phenotypes exhibit female, there are two genotypes: heterozygote (Aa) and homozygote (aa), and then mate with a male one which genotype must be homozygote (AA). Notice here: there is no female with aa genotypes in offspring. What does it mean? I think it means when body constant temperatures were determined and prefer ovary genes as dominant genes, the females with aa genotype were eliminated immediately, and there is only one female genotype: Aa, and from now on, heterozygote (Aa) takes the responsibility of being female. Day after day, the sex chromosome which always has the dominant genes started to shake off the Junk genes on itself, until only necessities left. I think this is the formation process of birds’ sex chromosome ZZ/ZW. Don’t worry, because one side is heterozygous diploid, and the other side is homozygous, so the sex ratio quickly returned to 1:1. 
 There is another question: some studies have shown that the differences between X and Y is much greater than between W and Z. I think that is because the genes of accessory gland on X chromosome are much more than on Z chromosome, for example mammals have secondary sex organs like uterine glands, uterus and the vagina on female, and ducts, glands and the penis on male, but birds almost don’t have any secondary sex organs, just have the primary sex organs. This is also the reason why WW and YY genotypes are lethal genes, because W and Y chromosomes have shaken off some genes which are essential in embryogenesis. On the contrary, in TSD animals there is no absolute dominant or recessive side, so either side has no chance to get rid of other genes.

5 Evolved from oviparity to viviparity
Five modes of reproduction can be differentiated in animals based on relations between zygote and parents:
Ovuliparity: fecundation is external (in arthropods and fishes, most of frogs)
Oviparity: fecundation is internal, the female lays zygotes as eggs with important vitellus (typically birds)
Ovo-viviparity: or oviparity with retention of zygotes in the female’s body or in the male’s body, but there are no trophic interactions between zygote and parents. (Anguis fragilis is an example of ovo-viviparity.) In the sea horse, zygotes are retained in the male’s ventral "marsupium". In the frog Rhinoderma darwinii, the zygotes developed in the vocal sac. In the frog Rheobatrachus, zygotes developed in the stomach.
Histotrophic viviparity: the zygotes develop in the female’s oviducts, but find their nutriments by oophagy or adelphophagy (intra-uterine cannibalism in some sharks or in the black salamander Salamandra atra).
Hemotrophic viviparity: nutrients are provided by the female, often through some form of placenta. In the frog Gastrotheca ovifera, embryos are fed by the mother through specialized gills. The skink Pseudemoia entrecasteauxii and most mammals exhibit a hemotrophic viviparity.
There are many types of viviparity, which can be divided into two broad categories: aplacental and placental viviparity. Apparently, placental viviparity is the most advanced mode of reproduction, during which the embryos are initially dependent on stored yolk but are later nourished directly by the mother through a placental connection. Do you ever think that mammals and birds are both warm-blooded animals, but why birds can’t evolve to viviparous stage? We have to figure out the difference between oviparous in birds and viviparous in mammals first?

Oviparous animals are those that lay eggs. Eggs can be deposited on land or in the water, and can have shells, or be unshelled. The key lies in once the eggs are laid; there is no more physiological investment from the mother. In other words, egg-laying, or oviparous, animals obtain all nourishment as they develop from the yolk and the protein-rich albumen, or "white," in the egg itself, not from direct contact with the mother, and the mother can’t give the baby anything before hatching, but only build and defend nests.

Viviparity, retention and growth of the fertilized egg within the maternal body until the young animal , as a larva or newborn, is capable of independent existence. The growing embryo derives continuous nourishment from the mother, usually through a placenta or similar structure, which is a special membranous organ with a rich blood supply that lines the uterus in pregnant mammals. In other words, baby can obtain nutrients from the mother continuously until childbirth, and mother have to pay additional nutrients as investment to supply the baby.

Apparently, whether obtaining additional nutrients continuously from mother or not is the key difference between birds and mammals. Now the question is why birds can’t choose the model of viviparity. I think the key problem is what kind of hormonal environment the mother located in, in comparison with baby's. The model of viviparity applies to only one case that, as long as mother is controlled by the recessive genes, the babies definitely can’t be affected by mother, whatever they had dominant genes or recessive genes. For example, in mammals XX/XY sex determination system, it is clear that the mother is controlled by female hormones, consequently she will pass the estrogen to offspring through umbilical cord. Since estrogen is the weak party, no matter what gender of the fetus, they will not be affected by female hormones from mother. Not vice versa, in birds ZZ/ZW sex determination system, we assume the birds also adopt vivipation as reproductive strategy, it is clear that the mother is controlled by female hormones, consequently she will pass the estrogen to offspring through umbilical cord, since estrogen is the strong party, if the fetus is ZZ genotype, he must be affected by estrogen from mother. Spotted hyena is a good example: because the mother's body contains a high level of androgen for some reasons, consequently genital development of the baby girl was inevitably affected by androgen from mother. Freemartin is another good example: because the twins shared the same placenta, and consequently the female one was affected by the testosterone from the male one. The above two examples illustrate that weak party will inevitably be affected by the strong sex hormones. In other words, strong sex hormones side is not suitable as the mother in viviparous strategy, and viviparous mode requires the mother to be controlled by a weak sex hormones, so she can’t interfere the offspring in sexual differentiation, while oviparous model doesn’t have this concern, because after fertilization, eggs separated from the mother without any intervention, including the ovo-viviparity, though zygote is still in the female’s body, there are no trophic interactions between zygote and mother. Therefore oviparous animals can be both XX / XY and WZ / ZZ genotypes, but viviparous animal can only be XX/XY genotype, I think there must have the contingency why mammals can evolve to viviparous era, and there must have the necessity why birds can’t evolved to the viviparous era.

Please don't forget the placental mode is bidirectional. In other words, babies not only get nutrients, oxygen and hormones from the mother through umbilical cord, but also pass the metabolic waste from themselves to the mother also through umbilical cord. I do believe that the metabolic waste includes the fetal hormone. In this area, I didn’t do any research, but in my some colleagues, the mother who carries boy always has more serious pregnancy reaction, like nausea, vomiting and much dark spots on face; and the mother who carries girl always has fewer symptoms like these. I think the reason is the testosterone produced by baby boy as supremacy affects mother's normal estrogen environment. This situation neither happens on the mother who carries baby girl, or the bird mother.

Of course, my conjecture has a premise first: in a stable constant temperature biological environment, the primary sex organ which was synthesized by dominant sex genes also produced dominant sex hormone. I think this assumption is reliable. Here are two examples: one is Freemartin that we always heard the baby girl had masculine appearance, but you never heard the baby boy had a feminine appearance due to the estrogen from mother or sister (AIS is another case); the other example is Sex-Change Chicken that sometimes we heard a hen can actually transform herself into a rooster under the right circumstances due to something wrong with hen's ovary, but a rooster can't transform himself into a hen unless the artificial injection of female hormones. Actually shemale in Thailand also share the same reason, and just the artificial injection of female hormones can't change the primary sexual characteristics, but secondary sexual characteristics. So I believe that only in single sex body with different sex alleles, such as XY or ZW, when the dominant party as supremacy has something wrong in expression, the recessive party can have the chance to play a role; in single sex body with same sex alleles, such as XX or ZZ, you must give her or him external intervention of strong sex hormone, if you want to change the sex. So we can conclude that in XX/XY mammals, female is the default sex, and in ZW/ZZ birds, male is the default sex.

6 The relationship between male and female
How do we define the relationship between sexes? Neither enemy nor friend, because friend or enemy depending on interests. I prefer the term“Cooperator”in reproductive strategy to define the relationship between two sexes. A woman is not born enemy to another woman, and a man is not born friend to a woman. No permanent friends or enemies, only permanent interests. So far we still can not distinguish between orgasm and reproduction, especially for women.

In fact, look at other animals except our mammals, their reproductions have nothing to do with any orgasms. We need to grasp the essence of a thing, not to be deceived by its superficies. With the development of IVF, we already know reproduction also can have nothing to do with sexual contact; with the development of surrogacy, we also can detach the mother from the sexual reproduction; I do believe in near future with the development of biotechnology, we also can detach the yolk from gamete or zygote. At that time, homosexual reproduction will come true, but now our human beings are still trapped in the cycle of chaos.

What is science? I think science is a process of truth-seeking. What is a process of truth-seeking? I think it is a process of error correction, because we are from barbarism and follow Law of the jungle or Might makes right, we distorted a lot of things in our history. Maybe we never know the true value of something, but we can be close to the truth step by step. Marx says we should doubt everything, I think he got half right. We could see further with much more effectively by standing on the shoulders of giants. Believe what deserve to believe, and suspect what deserve to suspect. Any truth should stand the test of time.

In some sense, Marx's theory of alienation is right, division of labor must lead the occupational dementia, but I don’t believe it can be eliminated in any time. I agree with Professor Zhou that  the only way to deal with the abuse of freedom is more freedom, so I think the only way to deal with the injustice during the division of labor is further detailed division. We need "Sexual liberation" instead of "sexual indulgence", and the sexual liberation means women should be liberated from the male sexual tools and birth machines. God bless us!