The problem is that we keep assuming that there is a point at which we became human. This is about as unlikely as there being a precise wavelength at which the color spectrum turns from orange into red. The typical proposition of how this happened is that of a mental breakthrough — a miraculous spark — that made us radically different. But if we have learned anything from more than 50 years of research on chimpanzees and other intelligent animals, it is that the wall between human and animal cognition is like a Swiss cheese.

Apart from our language capacity, no uniqueness claim has survived unmodified for more than a decade since it was made. You name it — tool use, tool making, culture, food sharing, theory of mind, planning, empathy, inferential reasoning — it has all been observed in wild primates or, better yet, many of these capacities have been demonstrated in carefully controlled experiments.

We know, for example, that apes plan ahead. They carry tools over long distances to places where they use them, sometimes up to five different sticks and twigs to raid a bee nest or probe for underground ants. In the lab, they fabricate tools in anticipation of future use. Animals think without words, as do we most of the time.

Undeterred by Homo naledi’s relatively small brain, however, the research team sought to stress its humanity by pointing at the bodies in the cave. But if taking this tack implies that only humans mourn their dead, the distinction with apes is being drawn far too sharply.

Apes appear to be deeply affected by the loss of others to the point of going totally silent, seeking comfort from bystanders and going into a funk during which they don’t eat for days. They may not inter their dead, but they do seem to understand death’s irreversibility. After having stared for a long time at a lifeless companion — sometimes grooming or trying to revive him or her — apes move on.

Since they never stay in one place for long, they have no reason to cover or bury a corpse. Were they to live in a cave or settlement, however, they might notice that carrion attracts scavengers, some of which are formidable predators, like hyenas. It would absolutely not exceed the ape’s mental capacity to solve this problem by either covering odorous corpses or moving them out of the way.