Cavemen once lived with modern humans for over 5,000 years and exchanged genes

Explaining this further, the first author and Ph.D. candidate at Leiden University, Igor Djakovic told IE, “During this period when Neanderthals and Homo sapiens likely co-existed in Europe, there were substantial transformations in material culture. It was likely a time when new ideas and knowledge were rapidly spreading through and between different human groups – possibly due to the increasing interaction between these two long-separated human lineages. It was, in all likelihood, a very interesting time to be alive.”

Archaeological evidence of the co-existence

According to Natural History Museum, Neanderthals first appeared approximately 400,000 years ago. Interestingly, they went extinct around the same time when Homo sapiens started to become the dominant human species i.e. about 40,000 years ago. So it is highly likely that at one point in time, the two species occupied the same regions.

During their study, the researchers examined two collections of artifacts (this term is used for referring to ancient man-made objects in archaeology) recovered from 17 archaeological sites in northern Spain and France. Radiocarbon dating of these artifacts revealed that the first collection comprised 28 Neanderthal artifacts and the second collection contained an equal number of objects created by Homo sapiens.

In order to further confirm their age and the human species to which the artifacts belonged, the researchers employed two advanced and widely accepted techniques known as Bayesian modeling (BM) and Optical Linear Estimation (OLE). The former is used to overcome the imprecision inherent to radiocarbon dating. It does not produce a single date but rather a probability range, for instance, the model estimated that modern humans inhabited northern Spain between 42,653 and 42,269 years ago.

OLE on the other hand predicts the extinction date of animals based on their last known appearances in the fossil record. It operates under the assumption that one can never in fact find or date the ‘first’ or ‘last’ member of a species. It uses the dates for the last known occurrences to estimate how much longer the species may have existed before its eventual extinction.

The data from the two methods suggested that Neanderthals went extinct between 39,894 and 39,798 years ago and their artifacts were in France and Spain for a time period ranging between 5,449 and 4,470 years. Since humans also inhabited the same region about 42,000 years ago (the exact range is mentioned in the paragraphs above), the authors calculated that both species thrived together in Europe between 1,400 and 2,900 years before the cavemen went extinct.

How did the two species react to each other?

Before we jump into the relationship that Neanderthals and modern humans might have shared with each other, it is important to understand that the findings of the authors do not point out the exact time and place where the two species may have co-existed. Moreover, the results predicted by the models are only as accurate as the data entered into them.

According to the researchers, the current results are based on the most robust, up-to-date, and high-quality data. However, when new evidence will come in from further radiocarbon dating of more samples, these models will have to be adjusted.

For now “we need to keep in mind here is the time depth – in all likelihood, there is no single scenario for the nature of their relationship when they co-existed in any given region. In some cases, they (Neanderthals and modern humans) probably lived together and raised children, in others they tried to avoid each other, and in some they probably had conflicts, Djakovic told IE.

“I suspect that they were likely more cooperative than we tend to imagine. We now know that they at least occasionally exchanged genes, as most people living today carry some Neandertal DNA,” he added further.

As part of their Neandertal Legacy project, Igor Djakovic and his team are currently conducting new excavations at a site in central France that preserves occupations of the last Neandertals in the region. They want to begin filling in the gaps concerning the nature and frequency of the interactions between Neanderthals and Homo sapiens prior to their disappearance.

The study is published in the journal Scientific Reports.