The Natural History Museum of Denmark currently hosts a fascinating exhibition on Neanderthals. These ancient humans are our closest living relative and serve as a window into our own past and what exactly it is that makes us humans. Apart from being interesting in their own right.

They were originally discovered in the Neander valley in Germany in 1856 and were the first hominin species to be classified. Our knowledge of them has come a long way since then, but there’s still much we don’t know — and much that we’re having to reconsider.

We’ve traditionally imagined these early humans as mammoth hunters and carnivores. But research is calling this one-sided view into question. Of course mammoths and other great mammals were on the menu, but moss, nuts, berries, and other non-animal foods were also significant. Possibly a lot more significant than anyone dared imagine just a couple of years ago.

This reframing of the Neanderthal diet is a story that scientists have only recently begun to piece together. It’s a story that’s based on diverse sources — from ancient poop to fossilized tooth plaque — and requires the most sophisticated technology available to researchers. And it hints at great diversity in the history of our extinct relatives.

It shows that we’re not the only human species that lived complex and diverse lives.

Neanderthals did not only live in frozen wastelands

It might seem self-evident, but until the advent of fast and cost-effective transportation such as container ships and airplanes, most human diets were based on what was immediately available in the environment. That’s why African cuisine is big on starchy vegetables, Asians eat tons of rice, and Europeans base their diets on wheat and other grains. (Centuries-old connections across the globe does complicate this narrative somewhat as many foods that play an important role in different parts of the world aren’t native to those areas, such as potatoes in Afroeurasia or apples in America.)

Following this line of thinking, Neanderthals likely evolved a diet based on the food available in their immediate environment. This doesn’t mean that they necessarily ate everything they could get a hand on, of course. They would have evolved to fill a certain niche in their environment where they could get all the nutrients they needed whilst keeping the number of competitors claiming the same food sources at a minimum. After all, it’s easier to stay fed if you’ve got your preferred food all to yourself. This basic biological fact is partly what gave long-necked giraffes an initial edge, driving their evolution.

Since Neanderthals roamed Europe and Asia at a time that was significantly colder than today, 400,000-40,000 years ago, it’s only sensible that a significant amount of their diet was indeed animal-based: it was what was available. Especially large mammals seem to have played a significant part in the diet. At least that’s the traditional view.

And it makes sense. In cold and arid regions where animals are one of the only available food sources, humans are likely to focus on large animals since they have greater layers of fat than small, lean animals. This is essential as humans can only safely subsist on around 35 % pure animal protein. Fat, however, contains tons of useful nutrients. The strategy of eating animals with tons of fat has nurtured indigenous populations in the Arctic regions of Canada and Greenland for centuries. It would’ve worked well for Neanderthals, too.

But not all Neanderthals lived in frozen wastelands. In fact, much of Europe was temperate during the 300,000+ years that Neanderthals roamed the continent.

This means that they had access to a wide range of non-animal foods including vegetables, mushrooms, fruits, and much more. Did they eat these foods? If they did, how important a part of their diet were fruits, berries, mushrooms, and nuts?

Fossilized dental plaque reveals past diets

Traditionally, studies of Neanderthal diets have used different techniques to reveal the chemical markers of different foodstuffs in the remains of Neanderthals. These studies have shown a remarkable level of nitrogen in Neanderthal bones, which is usually associated with meat-heavy diets. A study from the Max Planck Institute of Evolutionary Anthropology even analyzed the amino acids within Neanderthal remains, which showed that the high nitrogen levels were a product of a meat-heavy diet rather than fish or anything else — unlike in modern humans. The evidence would seem to point to Neanderthals being mostly carnivorous.

Yet the study above only definitively proved that some Neanderthals were mostly carnivorous. Since many Neanderthal fossils weren’t studied, the result doesn’t necesseraly apply to all Neanderthals. And some other studies do indeed point to a lack of meat-consumption amongst Neanderthals.

One of these is a recent study published in Nature which sequenced the DNA of dental calculus (fossilized tooth plaque, not weird mathematics) from Neanderthal teeth. It found that the DNA of one of the Neanderthal groups it analyzed pointed towards no meat consumption and instead a diet consisting of mushrooms, berries, and moss. It essentially found a vegetarian Neanderthal group.

However, two groups were analyzed. The non-carnivorous group lived in Spain whilst another group lived in Belgium. And whereas the Spanish Neanderthals didn’t eat meat, the Belgians ate almost nothing else, munching on woolly rhinoceros steaks all day long.

Neanderthal diets depended on where they lived. In the south, where non-animal foods were plentiful, the Neanderthal diet was varied. In the north, it was mostly carnivorous. A relationship that is also evident in modern human groups.

Neanderthal diets might reveal why they disappeared

The extinction of Neanderthals coincide wirth the appearance of modern humans in Europe. Since we possess Neanderthal DNA, we know for a fact that there was inmating between Neanderthals and modern humans. But researchers haven’t agreed on the degree to which this happened, nor whether other factors played a role in the extinction of our hominin relatives.

Diets might’ve played a role. If Neanderthals were mainly hunters of great game (at least in colder regions), then significant cooling could’ve put pressure on the large mammals that comprised their diet. These pressures would trickle down to those subsisting off great mammals, such as Neanderthals. Lacking food, they would either need to adapt, move, or die. Some researchers argue along these lines that climate pressures due to cooling played a significant role in the extinction of the Neanderthals. They believe that modern humans survived because we ate a more varied diet and thus adapted better to climate pressures.

This explanation might make sense in cold, northern regions, but it’s less convincing in southern regions, such as where the non-carnivorous Neanderthals from Spain lived.

Adaptability might still explain why our species survived where the Neanderthals died. Whilst all humans have been highly adaptable species, there’s evidence to suggest that ours is a significantly adaptable one. After all, modern humans succeeded in colonizing Australia 60,000 years ago, a feat that had consistently escaped other human species living for millennia on adjacent islands. This required modern humans to adapt to a whole new environment — the sea — in order to make landfall in numbers great enough to actually settle the continent. Such adaptability could’ve played an important role in securing more of the dwindling resources in Europe for modern humans over Neanderthals.

Interbreeding, dietary differences, and higher adaptability likely all played a role in helping modern humans survive climate change that killed Neanderthals. But aggression might also have played a role. Whilst the only thing we can say for certain about the interaction between different human groups concern interbreeding, as that’s the only evidence that we can study directly through DNA analysis, we can learn a lot about human behaviour towards other hominin species by studying apes such as chimps, bonobos, gorillas, and orangutangs. This is because we’re genetically very closely related, with much (although not all!) behaviour being universal across ape species and humans. It then becomes quite interesting to note that chimps, our closest relative, have been noted to war against gorillas, possibly over scarce resources. It’s not entirely unlikely, then, that lack of resources would’ve led to fighting amongst different hominin groups — just as it still leads to fighting between different groups of our own species today.

It’s impossible to say anything for certain, however. What is evident is simply that a lot of factors likely played a role in the extinction of the Neanderthals. Diets not only help explain this extinction due to a lack of great mammals, but also complicates it, since not all Neanderthals subsisted on carnivorous diets. Some earlier explanations simply don’t hold up to the modern evidence.

Just as today, the name of the game in human evolution was diversity and complexity 40,000 years ago. That was the whether you belonged to modern humans or Neanderthals. And it probably was for a host of other human species, as well.