For all the species humans have destroyed, perhaps the biggest question in our blood-soaked history is whether we were responsible for the speciescide of our nearest relatives, the Neanderthals. The debate has raged for decades, and is unlikely to stop soon, but the latest piece of evidence speaks in our favor.

Publishing in Nature, Professor Tom Higham of Oxford University re-examined the carbon 14 concentrations from 40 sites using improved mass spectrometry techniques and concluded that the tools associated with Neanderthal culture stopped being produced 41,030–39,260 ago.

This date, if correct, is highly significant. On the one hand it is earlier than some previous estimates, but on the other it suggests that there was an overlap pf 2,600-5,400 years with the arrival of humans in Europe. Such a long period of overlap contradicts the theory that humans simply moved in and exterminated the Neanderthals in a manner similar to the way we have wiped out many megafauna species.

“A mosaic of populations in Europe during the Middle to Upper Palaeolithic transition suggests that there was ample time for the transmission of cultural and symbolic behaviours, as well as possible genetic exchanges, between the two groups,” Highham and his colleagues write, consistent with increasing evidence some of our genes are of Neanderthal origin.

“Humans and Neanderthals were living contemporaneously for quite some period of time in different parts of Europe,” Higham says, supporting the idea that changes to Neanderthal artefacts shortly before they disappeared were a result of exchange with humans.

The new methodology was required because the Neanderthal disappearance occurs around the earliest point at which carbon dating can be used reliably. Higham has pushed back this point using a chemical pretreatment to remove contamination and particle accelerators to make the most of the tiny amounts of surviving radioactive carbon.

The increased accuracy this provides allowed Higham to track the arrival of our ancestors in different parts of Europe through a series of papers, with southwestern England, for example, colonized more than 40,000 years ago. Applying the same techniques to Neanderthal sites indicates Neanderthals disappeared from most of Europe around the same time, rather than being swept away by modern humans as we encroached on the continent.

Nevertheless, Clive Finlayson of the Gibraltar Museum, whose dating promoted the idea of a Neanderthal “last stand” in southern Iberia, argues that Higham’s technique is poorly suited to warmer sites. “I’m hugely worried that we’re building a castle in the air here,” he told Nature.

Higham admits that his work leaves open the question of why Neanderthals survived contact with humans for several thousand years, and then suddenly died out over a larger area, as well as why some genetic studies find interbreeding occurred during earlier contact, but not more recently. He hopes to explain these, saying, “I do like the idea that they aren’t really extinct and they do live on in us.”

Nature