A group of footprints left behind in muddy sands 80,000 years ago gives us a better idea of what a Neanderthal social group would have looked like long before Homo sapiens showed up to ruin the neighborhood.
A Stone Age slice of life
A rapidly growing set of archaeological evidence tells us that Neanderthals thought symbolically, made art and jewelry, buried their dead, and probably tended to their sick and wounded. We have direct evidence of what they ate, what kinds of tools they used, and how they made those tools. But when it comes to what kinds of groups they lived in and how those groups were organized, the best anthropologists can do is look at how modern hunter-gatherers live in similar conditions. If Neanderthals lived like hunter-gatherers live today, they probably spent most of their time in groups of between 10 and 30 people, mostly relatives, made up of a mixture of adults and children.
That lines up well with estimates of how many people could have lived in some of the Neanderthal living areas archaeologists have excavated. Those are good ways to develop ideas about Neanderthal social groups, but they're still indirect. On the other hand (ha!), archaeological evidence doesn't get much more direct than footprints.
Since 2012, archaeologists working at Le Rozel, Normandy, have carefully revealed 257 Neanderthal footprints, along with eight handprints, in a layer of fine, dark sand deposited 80,000 years ago. Scattered amid the remains of stone-tool manufacture, animal butchering, and fires, the prints preserve a ghostly snapshot of Neanderthals going about their lives.
And archaeologists can be reasonably sure the prints came from Neanderthals. Although evidence keeps pointing to the idea that early humans ventured much further, much faster than we've previously given them credit for, it's still a stretch to think that Homo sapiens (or anybody other than Neanderthals) would have been running around Western Europe 80,000 years ago.
Jeremy Duveau of France's National Museum of Natural History and his colleagues also compared the size and shape of the Le Rozel footprints to footprints from Homo sapiens and from much earlier hominins called Australopithecines (recorded in a trackway at Laetoli, Tanzania). The Le Rozel prints were proportionally wider, especially in the middle part of the foot, than Homo sapiens. And the Le Rozel prints suggested thicker, more robust feet with shallower arches than the average Homo sapiens–exactly what you'd expect based on the fossil remains of Neanderthal feet.
That makes Le Rozel a very rare, very important site, because so far archaeologists have found just nine other Neanderthal footprints at four sites scattered around Eurasia. And other than 64,000-year-old hand stencils traced on the walls of Spain's Maltravieso Cave, the eight handprints left in the mud of Le Rozel are the only Neanderthal handprints ever found.
A younger crowd
Most of the prints are just single steps preserved here and there, not lengthy sets of tracks. But they give archaeologists an idea of how many Neanderthals lived at Le Rozel at one time. In the Pleistocene dunes at Le Rozel, muddy sand would have held tracks well, and windblown sand would have quickly filled and covered them. As a result, archaeologists can be reasonably sure that all the Neanderthals whose prints show up in the same sediment layer were walking around Le Rozel at the same time.
Duveau and his colleagues say the prints record the presence of between 10 and 13 Neanderthals. That lines up with anthropologists' other estimates for the size of Neanderthal groups; the Le Rozel group seems to have been relatively small by the standards of modern hunter-gatherers, but not small enough to be unusual.
The footprints also provide clues about the makeup of the Neanderthal group, because scientists can use the length and of a footprint to estimate a person's height and build. For modern humans, anthropologists already know the average ratio of height to footprint length, but for Neanderthals, Duveau and his colleagues had to take a longer route. (Brace yourself: this gets a little esoteric.) From footprint length, it's easy to calculate the length of the second metatarsal (one of the bones of the mid-foot), because it correlates really well with the total length of the foot. And we have enough Neanderthals fossils to know that the second metatarsal is usually about 17% as long as the femur (the thigh bone), which is almost exactly the same as Homo sapiens. Femur length, in turn, can be used to calculate a person's total height.