New genomic research has revealed that Neanderthals and modern humans interbred over a longer period than previously believed, coexisting for approximately 7,000 years. This interaction, which began around 50,000 years ago as Homo sapiens migrated from Africa into Europe and Asia, has left a genetic legacy that persists in modern humans.
Tracing the Neanderthal Legacy in Human DNA
Approximately 1-2% of the DNA in individuals of Eurasian descent is of Neanderthal origin, with East Asians typically exhibiting higher proportions than those in other regions. The study sheds light on why some populations have more Neanderthal DNA than others, linking it to historical migration patterns and interbreeding events.
Led by researchers from the University of Rochester and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, the study analyzed both present-day human genomes and 58 ancient genomes extracted from bones and teeth of early Homo sapiens across Eurasia.
The researchers pinpointed the average time of Neanderthal-Homo sapiens interbreeding to about 47,000 years ago, refining previous estimates that ranged from 54,000 to 41,000 years ago.
Where Did the Interbreeding Occur?
Benjamin Peter, an assistant professor at the University of Rochester and the study’s lead author, suggests that the Levant region was a likely hotspot for early interactions between the species. Archaeological evidence supports this theory, as numerous Neanderthal settlements have been found in present-day Israel, Iran, Iraq, and neighboring countries.
However, Neanderthal DNA appears to be less prevalent in populations from the Gulf region, likely due to relatively recent migrations from sub-Saharan Africa, where Neanderthals were absent. This highlights how historical migration patterns shaped the genetic landscape of the Arab world.
How Researchers Made the Discovery
The breakthrough came from cutting-edge techniques in ancient DNA analysis. By examining fossilized bones and teeth of Neanderthals and comparing these samples to the genomes of contemporary humans, researchers identified a distinct pattern in the DNA sequence. High-resolution genomic tools allowed them to estimate the timeline for when this specific gene entered the human genome.
Why Do Some Regions Have Higher Neanderthal DNA?
The study also explored why East Asians have about 20% more Neanderthal DNA than Europeans or West Asians. One explanation is the longer period of interaction and interbreeding during early migrations into East Asia around 47,000 years ago.
“We show that the period of mixing was complex and extended over thousands of years,” Dr. Peter explained. “While some groups may have ceased interbreeding, others continued to mix for longer, leading to varying levels of Neanderthal ancestry across populations.”
Neanderthal Deserts and Beneficial Genes
Interestingly, certain regions in the human genome, known as “Neanderthal deserts,” lack Neanderthal DNA entirely. These areas may indicate that some Neanderthal gene variants were harmful to humans and were rapidly eliminated.
Conversely, other Neanderthal genes proved beneficial. Many of the surviving Neanderthal genetic traits relate to immune system function, skin pigmentation, and metabolism. These genes likely helped early humans adapt to the challenging Ice Age climates and new pathogens they encountered outside Africa.
“Neanderthals were well-adapted to their environments, and their genes may have provided an evolutionary advantage to modern humans,” noted Leonardo Iasi, a graduate student at MPI-EVA.
A New Timeline of Migration and Interaction
The study’s findings suggest that the initial migration of modern humans from Africa into Eurasia occurred more than 43,500 years ago, earlier than previously estimated. These early humans likely began interbreeding with Neanderthals soon after arrival, continuing for thousands of years.
This prolonged gene flow underscores the complexity of human evolution and highlights how interbreeding contributed to the survival and adaptation of early Homo sapiens in unfamiliar environments.
The Enduring Impact of Neanderthal DNA
As researchers continue to unlock the secrets of ancient genomes, it becomes clear that the story of human evolution is far more intertwined than once imagined. The genetic legacy of Neanderthals remains a critical piece of that puzzle, offering clues to how humans survived, thrived, and adapted to a changing world.
While some Neanderthal genes have faded from our genomes, others persist, a silent testament to the shared history of two species whose paths crossed thousands of years ago.
What does your DNA say about you? That question might hold more fascinating answers than we ever imagined.
