The public was extremely excited about the discovery of a new species of ancient human. The presentation of his bones became a major media event. But an anthropologist told DW a bit of scepticism is called for.
Two years ago, several skeletons belonging to an unknown species of early human lineage were discovered in the Rising Star Cave near Johannesburg, South Africa. Now, anthropologist Lee Berger and his team have presented their findings. The researchers are certain that they have discovered a previously unidentified human species. But this revelation gives rise to many questions. Anthropologist Christoph Zollikofer even says that several insights presented by Berger and his team are flat-out wrong.
DW: Does Homo naledi really belong to the hominin species?
Christoph Zollikofer: That is a typical media question. The term species is not a biological concept. In nature, there is basically no hard-set difference between individuals, groups and species. Instead, transitions are fluent between them. Of course, you can define life forms with two legs as humans to distinguish them from others. But it is questionable to do so if you look at the hand of a fossil that has been found. Hands are for gripping and climbing. Nomenclature works well for headlines, but not much else.
Is Homo naledi at least a new genus?
The idea that this is a new genus is just another headline-grabber. About 90 percent of this publication addresses the media and not the scientific community. I call this a "media species", which is usually quite short-lived.
Can it also belong to a previously discovered genus?
My intuition says it is a primitive Homo erectus. The combination of features is actually well-known. But I'm just speculating, since nobody knows its exact biological age. Assuming that it is two million years old, you could say it is an early Homo erectus, but not a new genus.
Is Homo naledi one of our ancestors?
We are not its direct descendants. It is not our direct ancestor. That's another media term. If you say ancestor, then any person on the street would think, "I'm its descendant." But quite the opposite holds true. If you find a fossil, you can be 100 percent certain that we are not direct descendants. But of course you can use the term ancestor in the figurative sense. Not everyone knows, however, that that is how the media means it.
Was the skeleton found in a prehistoric cemetery?
This is only one of many ideas that have been deliberately propagated in the media. I find it absolutely naive to assume there was a cemetery. It's typically human to always presume intent. When we look at a situation, we are always seeking patterns - we think someone arranged it that way. That says more about our way of thinking than it does about the fossils themselves. Biology is full of improbable situations that you cannot explain; yet they exist, and it is tempting to find a quick explanation for them.
And what about the bones in the cave?
If you look more closely at the site where the skeletons were found, the cemetery theory becomes less probable. Think about it: according to the publication, there had never been direct access to the Dinaledi chamber, where the bones were found. So our prehistoric human had to climb down there, squeeze through the narrow cave in complete darkness while dragging a corpse belonging to a member of its own species. From a purely practical standpoint, that makes no sense whatsoever.
Why is it so hard to determine the age of the bones?
The main problem is the sediments. In caves, you don't have a volcano that periodically erupts, leaving ashes that can be dated. From time to time, floodwater messes everything up and gigantic mounds form, like a garbage dump. The rocks there cannot be dated because the bones lie in loose sediment. They are obviously too old for radiocarbon dating - older than 50,000 years. That's all very inconvenient. There are also no objects made from animals accompanying the bones. The missing age is one of the great weaknesses of the publication. Everything's still up in the air.
How do you actually rate your colleagues' findings?
I would have spent more time on such a publication. We once made a discovery in Georgia. Seven years went by before our publication came out. There were things we simply did not understand and we worked for years to verify our findings. And of course we also discussed the question of "Shall we call it Homo georgicus now?" That would have been a great headline but it still would not have contributed to scientific debate.