Gorillas share genetic legacy with extinct lineage

Researchers from the University of Vienna in Austria and the Institute of Evolutionary Biology in Barcelona, Spain, recently published a groundbreaking study in the journal Nature Ecology and Evolution, shedding light on the evolutionary past of gorillas.

Leading the study were Martin Kuhlwilm, a scientist from the Department of Evolutionary Anthropology at the University of Vienna, and Harvinder Pawar, a Ph.D. student, along with Tomas Marques-Bonet, an ICREA Research Professor at the Institute of Evolutionary Biology. Collaborating with colleagues from the Sanger Institute, they employed advanced statistical methods, including neural networks, to analyze the genomes of gorillas.

Their research revealed a fascinating gene flow event in gorillas, who are genetically closely related to humans, wherein genes from an extinct lineage were passed down to present-day gorillas. This phenomenon is reminiscent of how modern humans and bonobos also retain genes from extinct groups in their genomes, evidence of ancient interbreeding.

Both humans and gorillas share an intriguing parallel in their evolutionary history. Over time, their DNA has been intermixed through mating with individuals from other groups that have since vanished, resulting in the introgression of genes from one group to another.

In the course of human evolution, there have been instances of gene exchange with Neanderthals and Denisovans, and traces of their genetic legacy can still be found in the genomes of many present-day humans.

Such studies on great apes, especially gorillas, are rare due to the scarcity of fossils for analysis of our close living relatives, unlike Homo sapiens. Consequently, the genomes of living individuals are crucial in reconstructing their evolutionary history, particularly given the threat of extinction faced by gorillas in the wild.

Gene flow from ghost population provides new insights into evolutionary history

In a groundbreaking study, a collaborative effort led by Tomas Marques-Bonet at the IBE and Martin Kuhlwilm at the University of Vienna, alongside Chris Tyler-Smith and Yali Xue from the Sanger Institute, delved into the genetic history of gorillas, revealing remarkable findings.

Gorillas consist of two species, each with two subspecies: Western gorillas, including the western lowland gorillas and cross river gorillas, and Eastern gorillas, comprising the eastern lowland gorillas and the closely related mountain gorillas.

The research involved analyzing the complete genomes of individuals from all four gorilla subspecies. Notably, they sequenced genomes from mountain gorillas in Uganda’s Bwindi National Park, one of the last refuges for these magnificent creatures.

Through innovative statistical methods, including the integration of neural networks, the researchers made a surprising discovery. Around 40,000 years ago, there was a gene exchange event between an extinct gorilla population (referred to as the “ghost population”) and the common ancestor of the eastern lowland gorillas and the mountain gorillas.

According to scientist Martin Kuhlwilm, approximately 3% of the modern eastern gorilla genome comprises remnants of genes from this ancient ghost population, which had separated from the common ancestors of all gorillas over 3 million years ago. Interestingly, no traces of this ghost population’s DNA were found in western gorillas.

This study provides valuable insights into the complex evolutionary history of gorillas, shedding light on how gene flow from extinct lineages has shaped the genetic diversity of present-day gorilla populations.

Gene flow from ghost population may affect gene functions

The international research team made a fascinating discovery highlighting the significance of genetic input from extinct ancestors in the evolutionary history of species. They demonstrated this through a compelling example: the presence of a gene responsible for bitter taste receptors that was introduced from the ghost population into today’s eastern lowland gorillas and mountain gorillas. This gene might have undergone positive selection, benefiting the current gorillas by helping them avoid consuming bitter and potentially poisonous foods.

Moreover, the analysis revealed an intriguing observation regarding the eastern gorillas. They possess a small amount of DNA from the ghost population on their X chromosome, which appears to be under negative selection. This phenomenon is also observed in humans and other species. The possible reason for this could be that the X chromosome exists in only one copy in male individuals, making harmful mutations more impactful.

Tomas Marques-Bonet, who is also a professor of Genetics at the Department of Medicine and Life Sciences (MELIS) at UPF, emphasized the study’s contribution to a better understanding of the evolutionary history of gorillas and the effects of gene flow from extinct populations on current ones.

Harvinder Pawar, the first author of the study, highlighted the importance of evolutionary genetics in differentiating humans from other apes, further emphasizing the significance of the team’s findings.

Source: University of Vienna

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