Recent studies have found that Neanderthal genes comprise between one and four percent of the genome of present-day humans. However, how many of those genes are still actively influencing human traits has largely remained a mystery.
Now, a multi-institutional team of researchers led by Cornell University has developed a set of computational genetic tools to clarify the genetic traces of interbreeding between humans of non-African ancestry and Neanderthals that occurred about 50,000 years ago.
The analysis revealed that, although some Neanderthal genes are responsible for certain traits in modern humans – including several with a substantial influence on the immune system – modern human genes seem to be winning out over successive generations.
The experts used a large dataset from the UK Biobank consisting of genetic and trait information for nearly 300,000 Brits of non-African ancestry. By analyzing over 235,000 genetic variants likely to have originated from the Neanderthals, they discovered that 4,303 of them are still playing a significant role in modern humans, influencing 47 distinct genetic traits, including how fast someone can burn calories, or the degree of natural immunity against some diseases.
In contrast to previous research that could not completely exclude genes from modern human variants, this study employed more precise statistical methods to zoom in on the variants attributable to Neanderthal genes.
“Interestingly, we found that several of the identified genes involved in modern human immune, metabolic, and developmental systems might have influenced human evolution after the ancestors’ migration out of Africa,” said study co-lead author April (Xinzhu) Wei, an assistant professor of Computational Biology at Cornell. “We have made our custom software available for free download and use by anyone interested in further research.”
Although the scientists used a dataset of almost exclusively white individuals living in the United Kingdom, the groundbreaking computational models they have developed could be used to gain evolutionary insights from other large and more diverse databases to better understand archaic humans’ genetic influences on present-day humans.
“For scientists studying human evolution interested in understanding how interbreeding with archaic humans tens of thousands of years ago still shapes the biology of many present-day humans, this study can fill in some of those blanks,” said senior author Sriram Sankararaman, an associate professor of Computational Biology at the University of California, Los Angeles.
“More broadly, our findings can also provide new insights for evolutionary biologists looking at how the echoes of these types of events may have both beneficial and detrimental consequences.”
The study is published in the journal eLife.
Neanderthals, or Homo neanderthalensis, were a species of hominins, closely related to modern humans. They are named after the Neander Valley in Germany where the first specimen was found. Here’s some key information about Neanderthals:
Neanderthals lived in Europe and Western Asia from about 400,000 to around 40,000 years ago, during the Pleistocene Epoch.
Neanderthals were shorter and stockier than modern humans, with a strong muscular build, a pronounced brow ridge, and a larger nose. These adaptations were possibly evolutionary responses to living in cold environments.
Neanderthals had a complex culture and were skilled tool makers. They used a technique called the Levallois technique to make tools, which involved striking flakes off a prepared stone core to produce uniformly shaped pieces. Neanderthals also used fire, lived in shelters, and there’s evidence that they buried their dead, suggesting some form of cultural or ritual practice.
Isotope analysis of Neanderthal bones suggests they had a high-protein diet that included a significant proportion of meat, although they also consumed plant material. Some studies have also indicated that Neanderthals may have used medicinal plants to treat illnesses.
The reasons for the Neanderthal’s extinction are not entirely clear, but possible factors include competition with modern humans, climate change, disease, or a combination of these factors.
Genetic studies have shown that Neanderthals interbred with the ancestors of modern humans and that non-African humans today have about 1-2% Neanderthal DNA. This interbreeding may have occurred in the Middle East, after modern humans left Africa but before they spread into Asia and Europe.
Certain genetic traits in modern humans, including some relating to immune response, skin color, and hair texture, are believed to be inherited from Neanderthals. In some cases, Neanderthal genes have been associated with increased risk for certain diseases, such as lupus, type 2 diabetes, and Crohn’s disease.
Our understanding of Neanderthals has significantly evolved and continues to do so, particularly with advancements in genetic analysis. They are now recognized to have been quite sophisticated, with a level of cultural complexity, genetic contribution, and possible symbolic thought or language capacity.