What killed the Neanderthals? This question has long been the topic of heated debate among paleoanthropologists, and the theories are numerous: Was it climate change? Volcanoes? Their inability to harness fire? Researchers now say in the Journal of Human Evolution that they have a new tool in the search for answers: rabbits.

While these bouncing, burrowing mammals were a big part of the modern human diet tens of thousands of years ago, Neanderthals—Homo neanderthalensis—didn’t have a taste for them. This small but significant detail could be key to understanding their demise. 

John Stewart, associate professor in paleoecology and environmental change at Bournemouth University, is part of a team comparing data on animal remains found at Neanderthal archaeological sites in Spain and Portugal with those found at modern human sites. What our ancestors ate is a good indication of how they lived, hunted, and adapted to their surroundings.

“It appears that basically modern humans were vastly more likely to hunt rabbits than were Neanderthals,” Stewart says.

This is perplexing, because rabbits would have been perfect targets; they exist in large numbers and would have been relatively easy to hunt, since they live in burrows. “You can harvest them if you’re clever,” Stewart says. But Neanderthals didn’t hunt them like H. sapiens did, and this proved deadly when the Ice Age took hold and many of the Neanderthals’ favorite protein sources (megafauna like mammoth and reindeer) were wiped out.  

“It would imply that basically this is why modern humans were able to survive into the colder period around 20,000 years ago,” Stewart explains. “As the climate deteriorated, Neanderthals were unable to turn their hand to resources like rabbits like modern humans were. This is why you see one human species surviving and the other not. It’s part of the whole pattern.” 

This study challenges the theory that competition with modern humans for resources is what killed the Neanderthals. “Differences are difficult to use as evidence for competition, because if you’re doing two different things, that implies you’re not competing,” Stewart says. 

Why Neanderthals didn’t eat rabbits remains a bit of a mystery, but Stewart speculates that perhaps they didn’t develop the tools to create traps. “One thing is clear: If you look at fauna records of modern humans, they seemed to be able to hunt a much broader variety of things, and presumably that’s because they had more tricks up their sleeves,” Stewart says.