Ancient DNA reveals previously unknown aspects of human evolution

Ancient DNA from human remains dating back around 45,000 years has given scientists new insights into human evolution. From this they were able to conclude that human populations have adopted favorable genetic variants fairly quickly. So far, this aspect of natural selection in human evolution has not been widely recognized.

Understanding the pace of positive selection in human evolution

The multinational study was published in the journal Natural Ecology & Evolution . The study looked at ancient human genomes to examine the role of natural selection in shaping biodiversity. To date, positive selection has been studied primarily using modern human genomic data, which can be prone to biases associated with unknown aspects of population history, particularly from the mixing of different populations.

In a report on the University of Adelaide’s website, Dr. Souilmi was quoted as saying, “It was widely believed that the genetics of our human ancestors were not altered by environmental stresses as much as those of other animals due to our improved communication skills and our ability to make and use tools.” However, by comparing modern genomes with ancient DNA, we uncovered more than 50 cases of an initially rare beneficial genetic variant that became common among all members of ancient human groups.

“Unlike many other species, the evidence for this type of adaptive genetic modification in humans is conflicting. This discovery consequently challenges the dominant view of human adaptation and gives us a new and exciting insight into how humans have adapted to the novel environmental stresses they faced as they spread across the planet.”

Ancient genomes shed new light on the history of human evolution

According to the University of Adelaide’s website, Dr. Tobler that studying ancient human DNA was critical to these new insights into human evolutionary history. “We believed that historical intermingling events between human groups may have hidden signs of genetic changes in modern human genomes. We examined the DNA of more than 1,000 ancient genomes, the oldest of which was around 45,000 years old, to determine whether certain types of genetic adaptations were more common in our history than studies of modern genomes suggested.”

Professor Christian Huber, Adjunct Fellow at the University of Adelaide and Assistant Professor at Penn State University, who is a senior author on the study, added that using ancient DNA is very important for the study because it predates major historical population mixing events took place had radically altered European genetic ancestry. This enabled them to capture historical signs of adaptation that cannot be gleaned 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 color from pre-migration hunter-gatherers. ( endrews21/ Adobe Stock)

The study team included researchers from the Mayo Clinic, the Garvan Institute of 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 evolutionary, environmental and conservation applications.

Genomic datasets have been rapidly becoming available to researchers studying human evolutionary history, accompanied by advances in statistical methods for detecting genetic signals of positive selection. However, such studies usually do not account for past phases of population mixing, which can alter genomic signatures and mask positive selection signals, leading to erroneous interpretations.

The University of Adelaide study circumvented this problem by examining ancient DNA that predated such human population mixing events. It also examined three modern European population datasets to determine the effects of Holocene admixture on modern European populations. This has led them to conclude that ancient human populations used positive selection and rapidly adapted to favorable genetic variants. As published in the paper Natural Ecology & Evolution says: “Through analyzes of ancient and modern human genomes, we show that previously reported Holocene admixtures have masked more than 50 historical hard sweeps in modern European genomes.”

Image above: Ancient DNA from human remains such as this depiction was used in the study. Source: Erin Cadigan / Adobe Stock

By Sahir Pandey