Thursday, October 08, 2015

Or is Homo naledi Actually Homo erectus?

California Magazine, from the University of California at Berzerkeley, has an article written by Glen Martin, in which he details the skepticism about the taxonomic status of Homo naledi, specifically, that it does not represent a new species.  Martin writes:
The popular science press went bonkers last month with news that fossilized bones of a previously unknown hominid had been discovered in a cave system in South Africa. Dubbed Homo naledi by lead researcher and University of the Witwatersrand paleoanthropologist Lee Berger, these proto-humans appeared to have lived somewhere between 1 to 3 million years ago, used tools, walked upright, and may have buried their dead, a practice that has only been attributed to our own species, Homo sapiens, and Neanderthals.

So there was a lot of talk of a “missing link”—the biggest find in paleoanthropology since Lucy, the skeleton of a female
Australopithecus, was excavated from a gully near Ethiopia’s Awash River in 1974. (Donald Johanson, the lead researcher in Lucy’s discovery team, founded the Institute of Human Origins, which later moved from Berkeley to Arizona State.)
As I mentioned in my post on the find, echoed by PZ Myers, at Pharyngula, this notion of a “missing link” is a straw man that has been created by the popular press and jumped on by organizations like the Discovery Institute and Answers in Genesis.  Martin continues:
Amid all the hoopla and confetti, however, a growing number of scientists are advising caution. They’re not denying the importance of the find; the fossils, they say, are invaluable. But they contend that the bones may not represent a new species. The evidence these skeptics point to suggests that the finds may actually be bones from
Homo erectus, the earliest known hominid to manifest the general proportions, stance and gait of modern humans. H. erectus had a long tenure on the planet, living from about 2 million to 70,000 years ago. The species was widely distributed (from Africa to East Asia and possibly southern Europe), used tools and fire, and may have constructed rafts to cross wide bodies of water.
Berger maintains that the skulls are too small, with too many primitive characteristics to be Homo erectus.  Once again, though, we come to the problem of how old the bones are.  Here, White is particularly critical:
One tibia, for example, was white on one end, a clear indication it had been snapped off in the recent past,” said White. “This (region’s) complex is extensive and like Swiss cheese, and it’s a favorite with spelunkers. You find beer cans next to fossils that are 3.5 million years old. So it’s important not to jump to conclusions.”
If the bones are late, as is possible, then the finds (or at least parts of them) might represent a Homo erectus population that has late primitive retentions. Even if there is more than one species present, there is no getting around the fact that the small, primitive cranium is where the Homo erectus traits are found, as well.

Berger is quoted as saying that this debate should play out in the published literature.  I suspect it will and that, eventually, we will figure out what sorts of primitive and derived traits the cache in the cave actually represents, even if we might never know exactly how old they are.

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