New Study Charts Neanderthal DNA through Human History

Among non-Africans, Neanderthal DNA makes up around 1-2% of the modern human genome. Ever since the Neanderthal genome was first sequenced from samples in a cave in Croatia, scientists have tried to understand how the other hominid’s DNA evolved with our own after mixing together 40-50 thousand years ago. That information can be used to gain insights into how different parts of the genome were important for our evolution. Previous studies looking at Neanderthal DNA in humans only compared ancient Neanderthal samples and modern human samples, making it difficult to look at change over time. A new study from the University of California, Berkeley charts this evolution by using data from ancient human samples.

The group of researchers compared Neanderthal samples to two sets of Homo sapiens samples, 59 ancient humans from the last 40,000 years and 275 modern humans from all parts of the globe, and found regions of Neanderthal DNA in the Homo sapiens DNA. To test if any of those parts of the genome impacted human evolution, they looked for any stretch with suspiciously high or low fractions of Neanderthal DNA. If the Neanderthal version was beneficial, they expected that it would be seen more than average, and vice versa for detrimental DNA. The group did not find a large difference in beneficial or detrimental Neanderthal DNA between modern and ancient Homo sapiens samples, signaling that natural selection happened quickly, within 10,000 years. The regions of the genome that were consistently more Neanderthal were related to skin pigmentation, metabolism, and the immune system.

The major limitation of any study looking at Neanderthal DNA is the number of Neanderthal samples available. This study used the only three high-quality Neanderthal genomes; enough to get a broad, but still limited, view. Some fraction of the human genome also comes from Denisovans, another archaic human species from Asia. However, there’s only one high-quality Denisovan genome, so scientists weren’t able to look at how their DNA evolved with us. More ancient samples, Homo sapiens and otherwise, will help uncover how we were changed by interspecies mixing.

This study was led by Leonardo Iasi, a PhD student at the Max Planck Institute, and Manjusha Chintalapati, a former postdoctoral researcher at the University of California, Berkeley.

Managing Correspondent: Alex Yenkin

Press Article: Human Population History, Pulse of Neanderthal Admixture Described in New Studies, GenomeWeb

Original Journal Article: Neanderthal ancestry through time: Insights from genomes of ancient and present-day humans, Science

Image Credit: “Neanderthal Mother (detail of diorama)” by Kojotisko.