New insights into the late history of Neanderthals

Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have sequenced the genomes of five Neanderthals that lived between 39,000 and 47,000 years ago. These late Neanderthals are all more closely related to the Neanderthals that contributed DNA to modern human ancestors than an older Neanderthal from the Altai Mountains that was previously sequenced. Their genomes also provide evidence for a turnover in the Neanderthal population towards the end of Neanderthal history.

Upper molar of a male Neanderthal, Spy 94a, from Spy, Belgium [Credit: I. Crevecoeur]

Due to the limited number of specimens and difficulties in obtaining endogenous DNA from such old material, the number of Neanderthals for which nuclear genomes have been sequenced is still limited. Since 2010 whole genome sequences have been generated for four Neanderthals from Croatia, Siberia and the Russian Caucasus. This Nature study adds five new genomes representing Neanderthals from a wider geographic range and from a later time period than what was previously obtained.

New methods for the removal of contaminating DNA from microbes and present-day humans that were developed by the Leipzig group have now enabled the researchers to sequence the genomes of five Neanderthals from Belgium, France, Croatia, and Russia that are between 39,000 and 47,000 years old. These therefore represent some the latest surviving Neanderthals in Europe.

Having genomes from multiple Neanderthals allows the researchers to begin to reconstruct Neanderthal population history. "We see that the genetic similarity between these Neanderthals is well-correlated with their geographical location. By comparing these genomes to the genome of an older Neanderthal from the Caucasus we show that Neanderthal populations seem to have moved and replaced each other towards the end of their history", says first author, Mateja Hajdinjak.

The team also compared these Neanderthal genomes to the genomes of people living today, and showed that all of the late Neanderthals were more similar to the Neanderthals that contributed DNA to present-day people living outside Africa than an older Neanderthal from Siberia. Intriguingly, even though four of the Neanderthals lived at a time when modern humans had already arrived in Europe they do not carry detectable amounts of modern human DNA. "It may be that gene flow was mostly unidirectional, from Neanderthals into modern humans", says Svante Pääbo, Director at the Max Planck Institute for Evolutionary Anthropology.

"Our work demonstrates that the generation of genome sequences from a large number of archaic human individuals is now technically feasible, and opens the possibility to study Neanderthal populations across their temporal and geographical range", says Janet Kelso, the senior author of the new study.

Source: Max Planck Society [March 21, 2018]