What Killed the Neanderthals? A Lack of Social Connection May Have Played A Big Role In Their Extinction

Scientists at the University of Montreal fed heaps of archaeological and ethnographic data into computer models that are typically used to study the distribution of flora and fauna. Instead, the algorithms were slightly tweaked to build a picture of different prehistoric human populations and their spatial distribution across Europe.

"Obviously, we don't have precise demographic data for populations living 35,000 years ago, so we used ethnographic data from better-documented ancient hunter-gatherer groups to set parameters for the geomatics tools and generate these models," Ariane Burke, a professor of anthropology at Université de Montréal and head of the Hominin Dispersals Research Group in Quebec, explained in a statement. 

"For example, these data show that the typical annual territory of a local group of 25 to 50 individuals, moving seasonally and maintaining regional connections with other groups, would be about 2,500 km² [965 square miles]."

The study focused on the period between 60,000 and 35,000 years ago, a tumultuous time that saw dramatic climate shifts, the spread of Homo sapiens across Eurasia, and ultimately the extinction of the Neanderthals. However, the team found that climate stress and direct competition with Homo sapiens couldn't fully account for the Neanderthals' disappearance.

What could help to explain their vanishing act, they argue, was connectivity. Homo sapiens tended to be associated with regions that are far more interconnected than those inhabited by Neanderthals. These well-connected regions were often strung along southern, coastal routes, keeping populations spread enough to remain in contact with neighbouring communities. In times of hardship, whether it be a climate upset or competition with other species, this proved decisive.

"These networks act as a safety net," explained Burke. "They allow for the exchange of information on resources and animal migrations, the forming of partnerships, and temporary access to other territories in the event of a crisis."

The paper also highlights how the Neanderthal population of Europe split into two groups under stress: one in the West, another in the East. In Eastern Europe, the groups were less well-connected and, by no surprise, they also disappeared first. In contrast, populations in the Iberian Peninsula, at the western edge of Europe, were better connected and held on to become some of the very last Neanderthals on Earth. 

"In western areas, the arrival of Homo sapiens may have added further stress, especially for Neanderthal populations that were already demographically vulnerable," added Burke. "Because the two species were capable of producing offspring together, their interactions were likely complex, involving competition, occasional interbreeding and other subtle population dynamics."

Homo sapiens are insatiably social creatures. It is our ability to connect, exchange, and engage with one another that has allowed us to build great cities, long-lasting civilizations, and inhabit every continent on Earth. If this research is on the money, our togetherness might also be what helped our species survive the challenges of the prehistoric age while all others fumbled. 

It's these same tricks, Burke says, that still play a role in human societies of the 21st century and our species' resilience. 

"Human migration has always existed, facilitated by mobility and social networks," Burke noted. "Even today, despite the complexities of borders, population densities and social inequalities, humans continue to migrate for the same fundamental reasons: to find more favourable areas, reunite with loved ones and join mutual aid networks."

The study is published in the journal Quaternary Science Reviews.