The mule is a thing that many people know, like a horse not a horse, like a donkey, but it combines the common characteristics of horses and donkeys. Horses are slightly more powerful, slightly larger, and good at running, while donkeys are less powerful and smaller, but have strong endurance. The offspring mules of a combination of horses and donkeys are characterized by both, with great physical strength and good endurance, and their body size is generally in between. The small size has the advantage of being small, and the advantage of mules on the winding and narrow roads in the mountains is obvious.
Mules are the product of the combination of horses and donkeys, originally these two organisms are independent species, separated and evolved in nature for a long time, although they are both ungulates, but the long separation has also led to a growing genetic difference between the two. The genetic differences are better, but the number of chromosomes in the evolution of horses and donkeys has changed greatly. Eukaryotes are particularly important in the process of hermaphroditic reproduction, requiring all the chromosomes to be combined into a sister chromosome group with all the genes for embryonic development.
The difference in the number of chromosomes between horses and donkeys means that the genes of the two are quite different, and the chromosomes of the germ cells formed cannot be perfectly paired, and the number of chromosomes necessary for eukaryotes to reproduce is not possible. The combination of horse and donkey is a relatively accidental event, and the reason is the genetic similarity between horses and donkeys, after all, the two are species of the same genus. However, the mules they produced were basically incapable of reproduction, that is, they also conformed to the concept of reproductive isolation, dividing horses and donkeys into different species, and unable to produce a new species population between the two.
However, among mammals, there are many species that originate from the same ancestor and have small differences in the number of chromosomes, and horses and donkeys can also produce mules by a bunch of chromosomes, which actually means that other species with similar differences may give birth to distantly crossed animals. Humans and chimpanzees are also very coincidental, only a pair of chromosomes, according to modern genetics and phylogenetics, humans and chimpanzees also have a common ancestor, the history of separation is not very long, in principle, humans and chimpanzees do have the possibility of hybrid offspring.
In biology, however, there is reproductive isolation between individuals of different species with significant differences in the number of chromosomes. Reproductive isolation can be complicated to say, but in fact, various factors cause organisms to communicate effectively. For humans, the definition of organisms is a species that can reproduce and evolve stably, and in the case of differences in the number of chromosomes, distant hybridization is difficult to achieve, and the offspring cannot be evenly divided when meiosis forms germ cells because the number of somatic chromosomes is odd. And most distal hybridized individuals do not develop their reproductive systems.
These are biologically part of reproductive isolation. In the vast majority of cases, genetic differences lead to differences in cell surface antigens, resulting in different biological germ cells are difficult to bind, chromosomal differences have a similar effect, so most distant hybridization is infertile, or can produce offspring by chance, but the offspring are difficult to produce because the reproductive system is not developed or can not produce germ cells. We often hear about mules, but rarely do we hear of mules combining with horses or donkeys to produce offspring.
Humans and chimpanzees have a similar relationship, and soviet scientists in history have hoped to create hybrid animals of humans and apes, and then perform heavy manual labor instead of humans, but the experiment was ultimately unsuccessful, and later due to ethical developments, most civilized countries banned such experiments. However, in the case of mules, if hybridization experiments with humans and apes are continued and carried out in large quantities, I personally believe that it is still very likely to breed hybrid animals of human apes, and modern technology is more advanced, and drugs can be used to suppress cellular reactions such as immune rejection.
Such experiments may not be available in the future, and with the development of national laws, such experiments that directly manipulate human genes and evolution can no longer be carried out. Humans and chimpanzees have a high degree of genetic similarity, chimpanzees have an extra chromosome, but in fact, human chromosome 2 and chimpanzee 2a, 2b chromosomes are highly homologous, with many homologous genes. Similar to the relationship between horses and donkeys, humans and chimpanzees do have a chance of producing hybrid offspring. However, human beings are more rigorous about their own gene pool, mainly human-centered, with humans as the most precious species.
Human beings are not completely separated from the influence of nature at present, human evolution is dependent on human continuous reproduction, genes continue to mutate, mutated genes undergo natural selection with the process of reproduction in the human population continues to spread, which is the reason why different human populations imagine this, is to ensure a large number of similar genes, skin color and other differences are due to natural selection in different environments. However, human cross-species hybridization may introduce genes that originally belonged to chimpanzees into humans, which can lead to instability that may lead to human genetic traits.
The technological development of modern humans does not require the creation of hybrid species like apes, and the development of ethics limits similar experiments, so we should never see the birth of a species like apes. However, the future may also be somewhat uncertain, because modern humans can already directly modify human genes, can introduce genes into the human body or eliminate a gene.