May 29, 2023
Ancient DNA from human remains like this representation were used in the study. Source: Erin Cadigan / Adobe Stock

Ancient DNA reveals hitherto unknown aspects of human evolution

Ancient DNA from human remains some 45,000 years old has given scientists new insights into human evolution. It enabled them to conclude that human populations adopted favorable genetic variants fairly quickly. Until now, this aspect of natural selection in human evolution has not been widely recognized.

Understanding the rate of positive selection in human evolution

The multinational study was published in the journal Nature Ecology & Evolution . The study examined ancient human genomes to examine the role of natural selection in shaping biological diversity. So far, positive selection has mainly been studied using modern human genomic data that may be prone to distortions related to unknown aspects of population history, in particular the admixture of different population groups.

A report on the University of Adelaide website quotes Dr Swilmy as saying: “It was widely believed that the genetics of our human ancestors did not change due to environmental pressures as much as other animals, because of our improved communication skills and our ability to make and use tools. However, by comparing modern genomes with ancient DNA, we discovered more than 50 instances of an originally rare beneficial genetic variant that was prevalent in all members of ancient human groups.

“Unlike many other species, the evidence for this type of adaptive genetic change has been inconsistent in humans. This discovery therefore challenges the prevailing view of human adaptation and gives us a new and exciting insight into how humans have adapted to the new environmental pressures they faced as we spread across the planet.”

Ancient genomes shed new light on the history of human evolution

According to the University of Adelaide website, Dr Tobler explained that examining ancient human DNA was critical to this new picture of human evolutionary history. “We thought that historical mixing events between human groups might have hidden signs of genetic changes in the modern human genome. We looked at DNA from more than 1,000 ancient genomes, the oldest being about 45,000 years old, to see if certain types of genetic adaptation were more common in our history than studies of modern genomes had suggested.”

Professor Christian Huber, Adjunct Fellow at the University of Adelaide and Assistant Professor at Penn State University, who is senior author of the study, added that using ancient DNA for the study was very important because it predates major historical population mixing events. had fundamentally changed European genetic ancestry. This allowed them to capture historical signs of adaptation that cannot be obtained from an analysis of modern DNA.

Previous studies showed that Europeans inherited blue eyes, lower cholesterol levels, higher Body Mass Index (BMI) and darker hair colors from pre-migration hunter-gatherers. ( andrews21/ Adobe Stock)

The study team included researchers from the Mayo Clinic, the Garvan Institute for Medical Research, the Max Planck Institute for the Science of Human History in Germany, the University of New South Wales and Massey University.

The Australian Center for Ancient DNA was established in 2005 to research and develop advanced ancient DNA for application in the fields of evolution, environment and conservation.

Genome datasets have rapidly become available to researchers studying human evolutionary history, accompanied by advances in statistical methods for detecting genetic signals of positive selection. However, such studies typically fail to account for earlier phases of interpopulation admixture that can alter genomic signatures and mask signals of positive selection, leading to erroneous interpretations.

The University of Adelaide study has sidestepped this problem by looking at ancient DNA that predates such human population mixing. He also studied three modern European population datasets to ascertain the impact of Holocene admixture on modern European populations. This allowed them to conclude that ancient human populations used positive selection and rapidly adapted favorable genetic variants. As the newspaper published in Nature Ecology & Evolution states, “Through analyzes of ancient and modern human genomes, we show that previously reported Holocene admixture has masked more than 50 historical hard sweeps in modern European genomes.”

Top image: Ancient DNA from human remains like this representation was used in the study. Source: Erin Cadigan / Adobe Stock

By Sahir Pandey

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