Last year the Rising Star expedition recovered more than 1,000 fossils from a cave in South Africa. After a year of intense analysis – just like I predicted – the results are in: they’ve found a brand new member of the human family. Called Homo naledi, this new family member has grabbed the attention of anthropologists, newspapers and creationists.
So what is it that makes H. naledi so exciting?
Well, it all stems from the fact that human evolution was a rather messy process. Different evolutionary pressures were driving different parts of our body to evolve at different rates. As a result most members of our family had a weird hodge-podge of characteristics. Such as early Homo erectus, who had pretty modern bodies but rather small brains. The technical term for all this is a “mosaic” anatomy.
Homo naledi is special because it’s the first such “mosaic” species with more modern, human-like traits than old, more ape-like ones. Or at least, we think it’s the first. They haven’t managed to date the fossils yet. They look pretty old, but that’s hardly a reliable metric. So take this significance with a pinch of salt. This similarity with later species is why the researchers decided to label it Homo naledi; placing it in our genus.
So in one sense this new fossil is the most exciting thing ever; marking the “transition” from ape to human (as much as a gradual shift in characteristics can be called a “transition”). On the other hand it’s also incredibly dull because it isn’t really telling us anything new. We already knew our family developed in a mosaic fashion.
What’s more, the specific changes seen in Homo naledi aren’t that unusual either. Other fossils indicate that our bipedal locomotion developed first (as seen in fossils like Lucy), followed by changes to the rest of the body (as seen in early Homo), finally with a big brain evolving (as seen in later Homo).
And Homo naledi fits neatly into that narrative too; with a more modern locomotive setup, slightly more modern body but an older looking brain. In other words, it’s exactly what you’d expect that “transition” to look like. The only really exciting part of its mosaic anatomy is that it has a more modern hand than we might have expected, suggesting increased dexterity (perhaps linked to early tool use) was more important earlier than we thought.
At least, that’s the general pattern. When you look a little closer some weird quirks start to emerge. Whilst most characteristics do fit in the overall narrative, there are a fair few that don’t. The brain is a slightly weird shape, it’s teeth are unusual and the feet aren’t quite right either. In other words, it was also experimenting with a few other features at the same time.
This is something else we’ve seen in other fossils. Australopithecus sediba is another mosaic species but with an experimental, unique way of walking. And the later Homo erectus had a few unique variants that cropped up over the course of it’s history.
It would seem that our family was evolving towards the modern human body in a mosaic manner. But every so often they’d try something a bit odd. Sometimes it would stick; a lot of times it wouldn’t. Homo naledi; as “human” as it is, also includes some of these experimental components.
So again, it’s actually a boring fossil in that it fits in with what we already suspected.
But that doesn’t stop it being one of the most significant finds of all time; helping confirm a lot of hypotheses about our ancestors. It might not tell us many new things; but it does help make the picture of our evolution much clearer and more solid.
In short, it’s science in action.