Ever since the initial discovery of Neanderthal bones in 1856, there has been a fascination with these ancient hominins. Questions arose about their similarities and differences with us as well as the nature of interactions with our ancestors. The emergence of another group known as Denisovans in Asia and South Asia introduced further inquiries.
A group of geneticists and AI experts are reshaping our understanding of early human history. Led by Joshua Akey from Princeton’s Lewis-Sigler Institute for Integrative Genomics, the researchers have uncovered a complex history of genetic exchange among ancient human groups.
Liming Li, a professor at Southeast University in Nanjing and a researcher in Akey’s lab, remarked, “This study marks the first instance of geneticists identifying multiple instances of modern human-Neanderthal interbreeding.”
Through their research published in the journal Science, the team revealed that modern humans have had prolonged interactions with Neanderthals for the majority of human history.
Contrary to the earlier perception of Neanderthals as slow and unintelligent, they are now recognized as adept hunters and toolmakers who exhibited advanced techniques in treating injuries and thriving in cold environments.
The researchers have utilized a genetic tool called IBDmix to examine the genetic exchanges between different hominin groups over the past 250,000 years. This tool enabled them to identify waves of contact occurring at different time intervals.
These findings challenge the existing genetic data that suggested modern humans originated in Africa 250,000 years ago and migrated out of Africa only 50,000 years ago. Akey’s team revealed a pattern of continuous movement and interaction between modern humans and Neanderthals, contrary to the previous belief of a static period followed by a single migration event.
The researchers also found evidence of cultural and technological exchanges between these human groups, aligning with archaeological and paleoanthropological studies.
By examining modern-human DNA within Neanderthal genomes, the researchers made a notable observation that offspring from early Neanderthal-modern human encounters likely remained with the Neanderthals, leaving behind no genetic traces in present-day humans.
The study also revised the estimated population size of Neanderthals based on genetic modeling, suggesting that Neanderthal populations diminished over time until they were assimilated into modern human communities rather than going extinct.
This assimilation model aligns with the hypothesis put forth by Fred Smith in 1989 and is supported by the genetic data presented in the research.
In conclusion, the researchers propose that Neanderthals were slowly absorbed into modern human populations due to demographic pressures, highlighting a continuous process of genetic interchange and assimilation over the past 200,000 years.
“Recurrent gene flow between Neanderthals and modern humans over the past 200,000 years,” by Liming Li, Troy J. Comi, Rob F. Bierma, and Joshua M. Akey, appears in the July 13 issue of the journal Science (DOI: 10.1126/science.adi1768). This research was supported by the National Institutes of Health (grant R01GM110068 to JMA).
