Around 37,000 years ago, small groups of Neanderthals inhabited southern Spain. Their lives might have been profoundly impacted by the massive eruption of Italy’s Phlegraean Fields a few thousand years earlier, an event that disrupted ecosystems across the Mediterranean.

Yet, they likely continued their daily routines—making stone tools, eating birds and mushrooms, engraving symbols, and crafting jewelry from feathers and shells—unaware they were among the last of their kind.

But their extinction story started tens of thousands of years before this. Neanderthals gradually became isolated and dispersed, ending a remarkable half-million-year existence in some of the most challenging environments of Eurasia.

By 34,000 years ago, Neanderthals had effectively vanished. Because modern humans and Neanderthals coexisted in the same regions for millennia, scientists have long debated whether our species contributed to their extinction, either through violence, disease, or competition for resources.

Recent research is helping to unravel this mystery, shedding light on the complex factors that led to Neanderthals’ demise.

According to Shara Bailey, a biological anthropologist at New York University, "We do know what happened to Neanderthals, and it is complex." Years of investigation suggest that competition between Neanderthal groups, inbreeding, and the arrival of modern humans all contributed to their extinction.

The Rise and Fall of Neanderthals

The story of Neanderthals took a modern turn in 1856 when workers in Germany’s Neander Valley discovered a skull that didn’t quite belong to any known species. Researchers dubbed it Homo neanderthalensis, and early theories characterized Neanderthals as primitive brutes. This view was based on a flawed reconstruction of a skeleton found in France.

However, more than 150 years of research have revealed a far more advanced species. Neanderthals created sophisticated tools, adorned their bodies, buried their dead, and possibly even had forms of communication. They thrived for hundreds of thousands of years in harsh conditions from Northern Europe to Siberia.

Archaeological evidence shows Neanderthals and modern humans coexisted in Europe for at least 2,600 years, and possibly as long as 7,000. This overlap occurred during a difficult time for Neanderthals, suggesting that the arrival of modern humans may have accelerated their decline.

Competition and Interbreeding

The relationship between Neanderthals and modern humans is complex. Tom Higham, an archaeological scientist at the University of Vienna, explains that in some regions, modern humans arrived after Neanderthals had already disappeared. In other areas, there was clear overlap, and the two species even interbred.

The first genetic proof of this came in 2010, when researchers sequenced the Neanderthal genome. Since then, DNA analysis has shown that Neanderthals contributed to the genetic makeup of all modern human populations.

However, by the time modern humans encountered Neanderthals, the latter were already facing significant challenges.

Genetic studies suggest Neanderthals had low genetic diversity and lived in small, isolated groups, which led to inbreeding and a "mutational burden." This meant many Neanderthal children were likely sickly, contributing to their population decline.

Even a slight reduction in infant survival rates could have led to extinction within a few thousand years, explains April Nowell, a Paleolithic archaeologist.

Neanderthals on the Brink

Neanderthals had already survived several near-extinction events, including two population bottlenecks around 135,000 and 100,000 years ago. Despite these hardships, they endured—until the added pressure of competition with modern humans tipped the scales.

While it was once believed that direct conflict, such as warfare or disease, wiped out Neanderthals, evidence of this is limited. Though some Neanderthal skeletons show signs of violence, there is no definitive proof that modern humans were responsible.

Instead, it’s likely that competition for resources played a larger role. Modern humans had certain advantages, such as more advanced tools, projectile weapons, and perhaps a greater ability to share and spread ideas due to larger, more connected populations. This gave them an edge in the struggle for survival.

A Complex End

The extinction of Neanderthals is not a simple story of one species wiping out another. Some Neanderthal populations may have perished from competition or disease, while others likely interbred with modern humans. As more humans moved into Neanderthal territories, the larger Homo sapiens population may have absorbed the smaller Neanderthal groups. Genetic evidence supports this idea, suggesting that modern humans didn’t so much eradicate Neanderthals as assimilate them.

The exact nature of Neanderthal extinction remains open to interpretation. Sang-Hee Lee, a biological anthropologist at the University of California, Riverside, points out that Neanderthal groups experienced varied fates. "Some Neanderthal populations died out, some were massacred, some interbred, and some exchanged ideas," she explains. The extinction of Neanderthals, then, was not a single event but a complex process shaped by many factors over thousands of years.

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