Ancient DNA reveals previously unknown aspects of human evolution

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

Understand the pace of positive selection in human evolution

The multinational study was published in the journal Nature ecology and 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 which may be susceptible to biases associated with unknown aspects of population history, particularly the mixing of diverse population groups.

A report on the University of Adelaide website quotes Dr Souilmi as saying: “It was widely accepted that the genetics of our human ancestors did not change due to environmental pressures as much as those of other animals, due to our enhanced communication skills and ability to make and use tools.However, by comparing modern genomes with ancient DNA, we have discovered over 50 cases of an initially rare beneficial genetic variant becoming prevalent among all members of ancient human groups.

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

Ancient genomes shed new light on human evolutionary history

According to the University of Adelaide website, Dr Tobler explained that examining ancient human DNA has been key to this new understanding of human evolutionary history. “We thought that historical events of admixture between human groups might have hidden signs of genetic changes in modern human genomes. We looked at the DNA of more than 1,000 ancient genomes, with the oldest dating back around 45,000 years, to see if certain types of genetic adaptation had been more common in our history than genome studies suggested. modern.

Professor Christian Huber, adjunct researcher at the University of Adelaide and assistant professor at Penn State University, who is one of the study’s lead authors, added that using ancient DNA for study was very important because it predated the major historical events of population mixing that had radically altered European genetic ancestry. This allowed them to capture historical signs of adaptation that cannot be obtained from modern DNA analysis.

Previous studies reported that Europeans inherited blue eyes, lower cholesterol, higher body mass index (BMI), and darker hair colors from hunter-gatherers before migration. ( drews21/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 for the research and development of advanced ancient DNA for application in the fields of evolution, environment and conservation.

Genomic datasets have rapidly become available to researchers studying the history of human evolution, along with advances in statistical methods to detect genetic signals of positive selection. However, these studies generally do not account for past phases of interpopulation mixing that can alter genomic signatures and mask positive selection signals, leading to misinterpretations.

The University of Adelaide study circumvented this problem by looking at ancient DNA that predates these human population mixing events. He also studied three sets of modern European demographics to determine 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 article published in Nature ecology and evolution states: “Through analyzes of ancient and modern human genomes, we show that previously reported Holocene-era mixing masked more than 50 historic hard sweeps in modern European genomes.”

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

By Sahir Pandey