(ORDO NEWS) — Regulatory fragments were found in the genome that evolved rapidly after the separation of our ancestors from great apes.
It was they who identified the most important features for humans, including a very large brain and a simplified, short intestine.
Compared to their closest relatives, chimpanzees and other members of the hominin family, humans are distinguished by their particularly large brains and short intestines.
These traits are considered not only essential to our species, but also mutually opposed: both the brain and the gut consume huge amounts of resources, and the body cannot afford to develop both.
The choice for the brain seems to have been made shortly after seven million years ago, after the split of our direct ancestral line from other great apes, but before the divergence from the Neanderthal line.
These conclusions were reached by geneticists from the American Duke University.
As a rule, the search for genetic features that are specific to our species are focused on genes – sections of DNA that code for proteins.
However, the DNA of humans and their closest relatives, chimpanzees, differ too little, and are almost identical in genes.
The main difference is in the non-coding regions of DNA, which can perform other important functions, primarily regulatory, controlling the functioning of chromatin and the genes themselves.
It is in these areas that geneticists from the team of Craig Lowe have concentrated. They found a number of fragments that changed rapidly after our ancient ancestors diverged from chimpanzees about 7.4 million years ago.
The scientists called them HAQERS (Human Ancestor Quickly Evolved Regions) and showed that they are involved in the development of the body, primarily the brain and intestines.
Being close to the corresponding genes, they regulate their work in the right place and at the right time.
“We see that not one mutation gave us a big brain and not one changed the intestines: it was a lot of changes that took place over time,” explains Professor Lowe.
“We see a lot of regulatory elements that operate in these tissues, determining which genes will be expressed and with what activity.”
The role of HAQERS was also confirmed experimentally. For this, scientists used laboratory mice, which, at the prenatal stage of development, had one of these fragments, HAQER0059, introduced into the cerebral cortex.
One group of animals received modern human HAQER0059, the other received a reconstructed version that was present in DNA more than six million years ago.
Indeed, modern HAQER0059 sharply increased the work of the genes responsible for the development of a powerful cortex.
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