As sex originate

Ben Esra telefonda seni boşaltmamı ister misin?
Telefon Numaram: 00237 8000 92 32

As sex originateAs sex originate? The answer is no – the puzzle to solve science of the XXI century. But there is a hypothesis: According to one of them, this is a side effect of the biochemical mechanism of repair of damaged genes that arose more than a billion years ago. Evolution has proven – Sex useful. Actually, we talked about this and so have guessed. Science has given to rational arguments.Sex has emerged from unicellular distant human ancestors more than a billion years ago. Almost all the a****ls (with very few exceptions) can reproduce sexually. Even jellyfish there male and female. Those a****ls that are deprived of the happiness (such as certain types of lizards), undoubtedly had ancestors that reproduce sexually.Why do we need sex?Sexual reproduction is so common in nature, that until the XIX century, people did not even wonder why a****ls and plants reproduce by mating or otherwise combination of gametes. This issue arose in the middle of the XIX century in connection with the theory of Charles Darwin on evolution and natural selection. After all, according to this theory to sexual reproduction was maintained, it should help the survival of the species, the “profit” should be more than sexual reproduction costs. Otherwise, for the continuation of the species – including human – nature would have found something better.Price sexual reproductionEvery action has its price. Propagation through sex – is also very expensive. Flowering plants are forced to work, produce nectar to attract bees to carry pollen from flower to flower, helping plants to carry out sexual reproduction. A male species Homo Sapiens, for example, have to buy the bright sports cars to attract the girls, the girls – well, we know that “The Devil Wears Prada” …In addition, only half of the sexually reproducing species – a female – to bear c***dren. If in a population of creatures that reproduce sexually, would have appeared mutant breeding budding, then ceteris paribus (eg birth on average 2 to 3 c***dren) the descendants of the mutant easily be pushed descendants couples sexual beings – all through 11 generations of difference offspring in an amount would be more than 1000 times (211/2 = 1024). Why do we still have to multiply sexually? The answer became clear only after the development of genetics.From the viewpoint of GeneticsCharles Darwin believed that the existence of sex advantageous for heterosis – the effect of the increased vitality of hybrids of different a****l species, are often observed in a****l husbandry: gaziosmanpaşa escort it is known, for example, that the mestizos of different breeds of horses run faster than their “clean” counterparts. But nature, it is clear to the races do not care – she is interested in the survival of the species. Thus Charles Darwin could not explain the nature of this effect, since in its time it was believed that the two parents heredity like mixed blue and red dye, resulting in cross – violet color.After the work of Gregor Mendel, August Weismann genetics and other pioneers of the XIX century explanation of the usefulness of sex was found. According to genetics, each person carries two sets of genes, one derived from the mother, the other – from the father. Moreover, due to the shuffling of genes in a process called crossing-over, a person gets a fairly complex collection of genes from all of their grandparents. However, genes are sometimes gets broken – defective. So, genetics has shown that a healthy gene derived from the father, can cover the negative effect of the defective gene, obtained from the mother, and – on the contrary. So it became clear observation of Charles Darwin on the increased vitality of hybrids of different a****l species.However, the persistence of the Métis is not the main advantage of sexual reproduction. Much more important is the possibility of a combination of several positive mutations. This phenomenon is most evident in bacteria. While the bacteria multiply by simple division, there are some kinds of sex as exchange of genetic material through a dedicated hose (pilus), bacteria which are connected to each other as during refueling aircraft in the air. In this way the bacteria communicate with each other resistance genes for each newly discovered medical antibiotic. Without sex bacteria it would take thousands of years to consistently acquire all the mutations that protect them from several antibiotics. Because of the sex they can acquire these mutations independently and then share “achievements.”SexEvolyutsiya puts on selfishExplanations of the usefulness of sex for survival of the species considered to be sufficient until 1962, when the British zoologist VaynEdvards began debate on the essence of Darwinism with the American biologist George Williams. Edwards believed that evolution selects types, and Williams was convinced (and could prove) that evolution selects individuals, selfish. According to Williams, the zeytinburnu escort hare in the forest does not compete with the wolf and the hare to another. If one rabbit will run slightly faster than the other rabbit, it is the other rabbit is eaten by the wolf, thus ensuring evolutionary victory first hare.In other words, any feature of an organism (including sex) is secured only in evolution if this feature makes it now is a specific individual, and does not mean all his future in the abstract. A large number of observations and mathematical models have confirmed the correctness of “individualist” Williams. Even further, this theory has been developed by Richard Dawkins, which is generally said that the true evolution of the players are not species or even individuals and genes. The body – this is only way to ensure a future for the gene.Politically incorrect sex After the book Dawkins’ The Selfish Gene “, many researchers have attempted to explain human sexual behavior as imposed by its genes optimal strategy transfer these genes into the future.Matthew Ridley, for example, showed how man evolved in small groups living in the African savannah. In this environment, genes tells him the man to have one wife, and the maximum number of mistresses. Wife – for c***dren birth, which he handed over his status in the group, and the mistress – the widest possible dissemination of its genetic material. A genetically viable strategy women, Ridley, was another – to become the wife of “a reliable earner” for the sustenance of c***dren, but in the time of ovulation to try to get the genes from accidentally running through a number of “pirate” with a “high-quality” genes than her husband.When people began to build cities and large states, this genetically viable strategy led to the formation of companies, where the majority of women were usurped great chiefs (kings) and specialized Don Juan. In China’s rulers of the Inca Empire, Babylon were thousands of concubines – and “beloved wife” for transfer status. In ancient Rome, the slave owners did not hesitate to use her for sexual purposes slaves, leaving the majority of men without women-slaves.According to Ridley, these trends have led to a lot of v******e and the low level of cooperation between women in the ancient world. In his book, Ridley suggested that the fall of the Roman Empire in the face of the Germanic barbarians it was partly due to the fact that the Germanic tribes existed firmly implanted sultangazi escort monogamy that helps men to unite against a common enemy – Rome.Why sex does not disappear?Biologist George Williams explained it this way. Suppose a tree grows in the forest. It produces thousands of seeds that may fall into a variety of places – sunny or shady, wet or dry. Therefore, it is important for the wood to produce various offspring – with more or less long roots, a different trunk height. Posterity will compete with each other, and the most successful will survive. In other words, Williams believed that sex produces a variety in which the brothers are competing with each other.The opposite hypothesis expressed by American biologist Michael Giselin. He believed that, on the contrary, sex and the associated diversity allows the brothers to avoid competition with each other, as they are taking a slightly different ecological niches. For an analogy, suppose that in a small village blacksmith’s family lives. If all five c***dren of a blacksmith inherited his craft, the four of them will die of starvation, since only one village blacksmith. But if they have different professions (weavers, roofers), their total income would be more, as they will not be competing for a place under the sun.The third hypothesis suggested American biologist Leigh Van Valen. It was called “Red Queen Hypothesis” by the name of a character from the works of Lewis Carroll. For the Red Queen from Carroll fastest run was the only way to stay in place. According to Van Valen, sex emerged as a way of individual pest. In the course of this struggle does not take place no victory – and the individual parasites are evolving at the same time, remaining in the same place relative to each other due to the simultaneous “arms race.”Finally, in the last two decades, a great contribution to the clarification of the question “Why do I need sex” made Russian-American biologist Alexey Kondrashov, who emigrated from Russia to the USA in 1991. According Kondrasheva theory, sex primarily need not useful combinations of genes and for the combination of the population and removing harmful genes. Each of us, a representative species Homo Sapiens, brings dozens of new mutations that were not present in our parents. Most of these mutations have no effect, some (about 1%) are harmful, a tiny part of the useful.Sex, by Kondrashov, allows you to collect a combination of bad genes in a small subgroup of individuals in size, after which the “special damage” killed, “cleaning”, like a vacuum cleaner, a population of deleterious mutations.The beginning of timeTheories Williams Giselina, Van Valen and Kondrashov explain why sex retains its usefulness and is not replaced, say, by budding. Unfortunately, they do not explain how the sex occurred. Hypotheses are many. Unknown – even more. Find the answer – the task of future science.

Ben Esra telefonda seni boşaltmamı ister misin?
Telefon Numaram: 00237 8000 92 32