only humans?
The orangutan in the zoo, when people look at it, they can't help but imitate it or do some funny actions.
The orangutan might feel very happy after seeing it, because in its view, the human is the "monkey".
Darwin 's theory of evolution has influenced modern biological evolution research, but at the same time, more and more scientific research has proven that human ancestors indeed belong to the category of orangutans, to be precise among primates. The great ape later evolved into hominid and became a unique species.
It is not unreasonable that humans and orangutans are so similar , especially chimpanzees family .
According to a 2005 US research report, the human genome is very similar to that of chimpanzees at the DNA level.
Scientists found that the genetic codes of the two are very similar. In a direct comparison between the two genomes, the similarity of the DNA sequence reached 98.2% .
The genetic similarity is extremely high
In addition, scientists have discovered that a small part of the DNA in our bodies is only shared with bonobos, not chimpanzees.
-related differences suggest that the ape ancestors that gave rise to humans, chimpanzees, and bonobos were both large and genetically diverse .
Human ancestors separated from the ancestors of bonobos and chimpanzees more than 34 million years ago, but the two later retained this diversity until their populations completely split into two groups 1 million years ago.
But the question is, why are humans and chimpanzees so genetically similar, yet so different in their behavioral patterns and evolution? The difference between the two is mainly concentrated in the 1100 different genes contained in the X chromosome . Each gene affects specific characteristics of the body.
Humans have too many similarities with orangutans.
For example, EM8, it will affect blood coagulation and is related to leukemia. , CPX is related to facial development, cleft palate, OPN1LW is related to red vision, etc. The 1.2% difference in
brings about 35 million differences. Although a large part of them has little impact on individuals, the differences bring about qualitative changes.
So when and where did humans separate from apes and become an independent branch of bipedal animals?
Evolutionary relationships of Hominidae.
As early as 3 more than 3 centuries ago, Dutch anatomist Nicholas Tulp and 18th century naturalist Carl Linnaeus both studied this problem. The most famous one is Darwin, who was also two man's successor.
The discovery of modern anatomy shows that , Gorillas and chimpanzees are the closest to humans, and no species is so close to humans.
Revelation of reproductive isolation
In the mid-1960s, David Pilbeam of Harvard University suggested that Ramapithecus might be the earliest member of the human lineage.
Of course, some people believe that in the 30 million years of human evolution , the evolutionary process has been so long that it is not so simple to determine the ancestors.
In addition to Ramapithecus, African apes are also potential targets.
Humans are actually orangutans
Judging from the above situation , humans have great similarities with primates It seems that does not bring changes to other primates as much as .
Or, in other words, why humans, who are also primates , did not hybridize with other primates during the evolution process, and develop other different groups.
Reproductive isolation between primates and humans is not a secret today. Modern science tells us that reproductive isolation is mainly determined by chromosomes. The pairing of chromosomes and the combination of genes are the key to forming species. The
chromosome expresses the
polyploid , i.e. the doubling of the chromosome complement may give rise to a new species within one generation, separated from its ancestral species.
For example, tetraploid plants crossed by diploid ancestors will produce sterile hybrid offspring, a situation that is more common in angiosperms.
chromosomal rearrangement concepts , Robertson fusion, fission, translocation, and inversion may play a role in species.
Many related models indicate that chromosomal rearrangements accelerate gene diversification between populations, so promotes speciation .
A complete set of genetic information consists of 46 chromosomes
Scientists considered two types of models, which became the " mixed dysfunction " and " suppressed recombination " models of speciation. The
hybrid dysfunction model suggests that recombination with between rearranged chromosomes produces gametes in which some chromosomal segments are deleted.
and others will be copied, resulting in further partial reproductive disorders .
This is because heterokaryotic hybrids will show low levels of reproductive fitness, which is called " disadvantage ". The process of
chromosomal rearrangement
chromosomal rearrangement may first be established in a small local population through random drift, regardless of whether the area where the ancestral species was distributed was peripheral or internal. If
individuals show high fitness in this region and promote the evolution of the prezygotic segregation mechanism , this will inhibit hybrid formation.
The model further states that if the fitness of the hybrid decreases , the chromosome mutation will be selected, and then will eliminate from the population. Overview of Possible Prezygotic Segregation Mechanisms for
is unlikely to have established chromosomal rearrangements in its ancestral population that reduced the fitness of heterozygotes despite the small probability of random drift.
Especially when the hybrid disadvantage of and is only very slight, the natural selection of reproductive isolation will also become very weak.
Human chimpanzee chromosome map
Scientists have confirmed in genetic studies of human speciation that a large number of chromosomal rearrangements have occurred between humans and chimpanzees.
Especially the nine chromosomes show the phenomenon of centralization among human nuclear chimpanzees. The nine chromosomes of
include 1, 4, 5, 9, 12, 15, 16, and 17. Among them, human chromosome 2 represents the fusion of two acrocentric chromosomes present in chimpanzees. The other chromosomes of
are numbers 12 and 13. If these chromosomal rearrangements occurred early in the divergence of chimpanzee and human ancestral populations, then their preference for the allele in the differentiated populations would be trapped on the chromosome barrier.
Human and Chimpanzee Chromosome 7 Infographic
This can therefore lead to genetic divergence between the two groups as they adapt to their different prevailing environments, and the accumulation of incompatibilities can gradually lead to reproductive isolation and speciation.
Human and orangutan
DNA sequencing , scientists can now use more advanced techniques to conduct genetics research, allowing them to identify reproductively isolated loci on a genome-wide scale and compare them across different lineages.
Related research shows that , sex chromosomes may be an important driver of reproductive isolation in most animal taxa, including humans.
Modern science has shown that hybridization existed in ancient humans , The Y chromosome sequence of Neanderthals has not been found in the modern human genome, and many of the genes come from the reduced areas of ancient human ancestors, namely desert areas.
Many discoveries have shown that the X and Y chromosome regions may have been involved in reproductive isolation during hybridization, so selection of unsuitable hybrids would limit the introgression of sex chromosomes and quickly eliminate ancient ancestors.
Scientists are trying to solve this problem by identifying regions of the genome that are consistent with the reproductive isolation signature between the two modern primate populations in areas of natural interbreeding.
Hybridization in human evolution
Scientists have identified a broad and continuous X chromosome sequence . Its region shows high conservation with human and howler monkey X chromosome , which is consistent with the conservation of the X chromosome in mammals.
has reduced gene penetration of the X chromosome compared with the autosomal , a genomic signature resulting from postzygotic reproductive isolation.
Scientists' experimental results suggest that selection may shape introgression of X chromosomes and autosomes differently.
Human X chromosome mapped from primate hybrid zone
Final results reveal , significantly reduced levels of introgression structure.
In other words, The reproductive isolation of humans and chimpanzees has been reflected in the gene itself , which is like the wrong key failing to open the right door.
The human species has experienced quite rapid changes in the process of evolution. We have no opportunity or time to merge with primate genes during the changes in genetic development.
This determined the path of human evolution from the beginning. The world is destined to follow its own path, and we have no way to solve the problem of reproductive isolation.
Studying human origins and searching for human ancestors can provide more and deeper insights into the evolutionary history of humans, such as ape species diversity, studying population explosion from a genetic perspective, etc.
This is the opportunity given to mankind by nature, which ultimately allows us to stand on this planet and overlook everything.
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