Study links ancient virus to human-chimp brain divergence

Research published in the journal "Science Advances" indicates that chimpanzees might have possessed brains similar to those of humans were it not for the intervention of an ancient virus during their evolutionary path. The findings highlight unexpected factors that may have contributed to the biological differences between the two species.

The genetic similarity paradox

Humans and chimpanzees share a high degree of genetic convergence, with DNA differences accounting for only approximately 1.2%. Despite this small percentage, the specific locations and nature of these variations play a crucial role in defining the distinct biological traits of each species.

Scientists focused on a specific gene named "LINC00662," which is active in humans during the early stages of brain development. This gene assists nerve cells in maturing and forming extensions, including dendrites and axons, which enable neurons to exchange information.

Viral impact on gene activity

Although the "LINC00662" gene exists in chimpanzees, it remains inactive in them. Researchers discovered traces of an internal retrovirus known as "PTERV1" near this gene, leading to the hypothesis that the virus affected the gene's activity in chimpanzee ancestors millions of years ago, thereby influencing brain evolution.

To test this theory, researchers used miniature models of brain tissue. Experiments demonstrated that disabling the "LINC00662" gene hindered the natural maturation of nerve cells and prevented the formation of extensions required for signal transmission.

Limitations of current findings

The hypothesis remains inconclusive. It cannot be determined whether a similar virus present in the genome of human ancestors millions of years ago would have disabled the same gene or altered the trajectory of brain development. Additionally, the resulting brain structure and intellectual or behavioral capabilities are unknown, as these traits depend on complex interactions between DNA regions and numerous other genes.

The study underscores the potential role of viruses in the evolution of living organisms, suggesting that remnants of ancient viral infections in DNA can contribute to biological differences between species. Traces of the "PTERV1" virus are found not only in chimpanzees but also in other African great apes, while humans do not carry known traces of this virus in their genomes.