Humans competed with carnivores for cave space

Would you want to share your home with a 100-kilogram carnivorous hyena? Probably not. Neither, it seems, did the Denisovans.

These early humans turn out to have been just short-term visitors when they left tools and remains at one of the world’s most famous archaeological cave sites.

For most of the past 300,000 years, the real owners of the Denisova Cave in southern Siberia have been large carnivores, especially cave hyenas – deeply unsuitable housemates for humans.

A new study by Russian and Australian scientists, led by Mike Morley from Flinders University, Australia, shows that human occupation of the site seems to have been sporadic – despite the plethora of tool fragments. And those early humans who did take refuge in the cave may have used fire less than expected.

The dig site in the foothills of the Altai Mountains has been in the spotlight following the discovery in 2010 of the previously unknown Denisovans, who used the cave between roughly 200,000 and 50,000 years ago, and may have shared it with Neanderthals at times. More recent discoveries have included a first-generation Neanderthal–Denisovan offspring.

That’s significant of course, but writing in Scientific Reports the team notes that the human DNA and fossils found at the site are only a tiny fraction of the material recovered, and thus only a small part of the cave’s story. 

The rest, particularly the abundance of coprolites – fossilised animal poo – helps to complete the picture of what was going on in this important shelter during the Middle Pleistocene and after. 

The microscopic study of intact sediment blocks collected from the Main and East Chambers shows that the cave was occupied almost continuously by large animals throughout the past three glacial–interglacial cycles.

The researchers have been able to attribute the bulk of the coprolites to cave hyenas (Crocuta crocuta speleans). You wouldn’t want to meet one of these in a dark cave: they were much bigger than their African cousins and hunted horses, bison and woolly rhinoceros. This formidable, once-abundant Ice Age predator became extinct about 14,000 years ago for reasons that are still not fully understood.

Other coprolites have been left by wolves, and there are also signs of sedimentary disturbance by large animals such as cave bears.

By comparison, microscopic traces of human activity are scarce – perhaps not surprising given the company.

While charcoal found in the samples shows that the early humans used fire, the small amount discovered suggests that the Denisovans were not prolific pyrotechnicians.

The researchers point out that this might reflect where the samples were collected – a confined space perhaps unsuited to fire – but note that the shortage of fire-making evidence is still intriguing.

Co-author Richard Roberts, from the University of Wollongong, says the study is very significant because it shows how microscopy and other modern archaeological science tools can extract important insights from sedimentary material.

“Using microscopic analyses, our latest study shows sporadic hominin visits, illustrated by traces of the use of fire such as minuscule fragments, but with continuous use of the site by cave-dwelling carnivores . . . which are very unlikely to have co-habited with humans.”

The researchers say further work is needed to discover what organic materials, such as DNA and lipids, can be recovered from the coprolite fragments.