The recent discovery of 1,500 pieces of teeth and bones has made headlines in the media. While some are willing to hail Homo naledi as a human ancestor, others take a more cautious approach.
Paleoanthropologist Lee Berger and his colleagues published a paper on their discovery in the journal eLife. It seems that the discovery raised some doubts at an early stage, as they did not choose a more prestigious journal, such as Nature or Science or PNAS.
Or maybe they did, but their paper was turned down.
H. naledi could be on its way out at this early stage.
Writing in Newsweek, Jeffrey Schwartz, professor of biological anthropology at the University of Pittsburgh, takes a very sceptical view of Homo naledi:
“Why is it a species of Homo? Because some specimens seem to be like us. Why australopith? Because other specimens have some of their features. Why do all belong to the same species? Because they were found in the same cave, but the published images tell a different story.”
He then goes on to say what is wrong with this assumption:
“Viewed from the side, two partial skulls are long and low, with a long gently sloping forehead that flows smoothly into the brow – nothing like us, or most specimens regarded as Homo. A third partial skull is very short and rounded, with a high-rising forehead that is distinguished from a distinct, well-defined brow by a shallow gutter – not like the other skulls, and not like us or most specimens regarded as Homo. The femur has a small head (the ball end that fits in the hip socket) that is connected to the shaft of the bone by a long neck, and, below the neck, is a "bump" of bone that points backward. These features are seen in every australopith femur. In us, and all other living primates, the head of the femur is large and the neck short, and the "bump" points inward. Further, the teeth are very similar to those from a nearby fossil site that has yielded various kinds of australopith. Even at this stage of their being publicized, the 'Homo naledi' specimens reflect even greater diversity in the human fossil record than their discoverers will admit.”
Finally, he gives some advice:
“What to do? As I recently advocated in the journal Science, it's about time paleoanthropologists acknowledged what a taxonomic and undefinable mess the genus Homo has become, and restudy the human fossil record without preconceived notions and the historical weight of overly used names. We must start from scratch, comparing in greater detail than usual specimens in order to see how they sort out, first into groups one might call by species, and then into larger groups we may give genus names to. It may be necessary to revive genus names that had been proposed early on, but what I predict is that we will see a picture of hominid taxonomic diversity that mirrors the diversity of virtually every other animal [sic].”
A further problem with H. naledi is that the bones – or the cave – have not been dated.
What many scientists are reluctant to admit, is that the gulf separating humans and apes is simply too wide. Nothing can make an ape-like being into a human in any time.
Schwartz, Jeffrey H. 2015. Why the Homo Naledi Discovery May Not Be Quite What it Seems. Newsweek (10 September).