Why did Neanderthals vanish thousands of years ago? Professor Chris Stringer, of the Natural History Museum, on the latest revealing research

© The Trustees of the Natural History Museum, London

Britain: One Million Years of the Human Story is at the Natural History Museum, London until September 28 2014.

“Neanderthals are our closest-known relatives, and research has recently shown that nearly all humans alive today have a small percentage of Neanderthal DNA in their genomes.This interbreeding probably occurred soon after small groups of early modern humans began to leave their African homeland about 60,000 years ago.Determining what happened after that and when Neanderthals disappeared as a population has been hard, because the favoured method of radiocarbon dating can be increasingly unreliable beyond 30,000 years ago.Radiocarbon dating on material older than 30,000 years old is more significantly affected by contamination, which can make samples appear younger by many thousands of years.An international team, led by scientists in Oxford, has applied the latest methods to remove contamination, and radiocarbon dated 196 new samples of bone, charcoal and shell from key Neanderthal sites ranging from Russia to Spain.The results are striking: Neanderthals seem to have disappeared over that entire area before 39,000 years ago.The team also dated so-called ‘transitional’ stone tool industries that are believed to be either the product of some of the last Neanderthals in Europe or some of the earliest modern humans.These were all between 40,000–45,000 years old, which may indicate a period of co-existence between these two human groups in Europe, before the Neanderthals became extinct.Significant interbreeding between Neanderthals and early modern humans had probably already occurred in Asia more than 50,000 years ago, so the dating evidence now indicates that the two populations could have been in some kind of contact with each other for up to 20,000 years, first in Asia then later in Europe.This may support the idea that some of the changes in Neanderthal and early modern human technology after 60,000 years ago can be attributed to a process of acculturation between these two human groups.Of course, samples from some sites did not produce dates at all, and the coverage did not extend to eastern regions such as Uzbekistan and Siberia, where Neanderthals are also known to have lived, so it is still possible Neanderthals lingered later in some areas.But the overall pattern seems clear – the Neanderthals had largely, and perhaps entirely, vanished from their known range by 39,000 years ago.A severe Heinrich event, characterised by cold and dry conditions, hit Europe between 39-40,000 years ago, and it remains to be seen whether that event delivered the coup de grâce to a Neanderthal population that was already low in numbers and genetic diversity, and trying to cope with economic competition from incoming groups of Homo sapiens.”