Tuesday, May 9, 2017

Discoveries in the Lesedi Chamber and the Date of Homo naledi

The skull of Neo (Homo naledi) from the Lesedi Chamber
Courtesy Wits

OK, now that I got that off my chest, here is a brief summary of the new Homo naledi findings.  This is less exciting than the original find, since I knew from the book what was coming.  Nevertheless, it's extremely satisfying to finally get the technical details.  They do not disappoint.

First up, we have the paper describing the date of Homo naledi.  They used uranium series dating, electron spin resonance, radon loss, uranium-thorium dating of flowstone, and paleomagnetic dating to arrive at a conventional date of 250,000 years old for the remains of Homo naledi.  This is considerably more detail than what was described in the leaked book chapter, which may well account for the delay of the book.  Actually, this seems like more than we usually get in a fossil dating paper, but honestly, this work is way outside of my expertise so I really can't say much more.  The date is definitely much younger than "early Homo," which is conventionally dated to around 2 million years old.  So Homo naledi looks like "early Homo," but it's much younger.  Surprise!

Next, we have a paper describing the excavations in the Lesedi chamber, a second site from the same cave system about 100 meters away from the Dinaledi chamber where the original fossils were found.  Excavations at the second site yielded a partial skeleton and skull named Neo by the discoverers.  "Lesedi" means "light" in Setswana, and "neo" is "gift" in Sesotho.  Even though the skull is not as complete as I imagined it would be, the paper describing Neo is a magnificent work with lots and lots of comparative data.  This is going to be a very fun read.

The Lesedi chamber is described as almost as inaccessible as the original Dinaledi chamber, and they report 131 hominin specimens.  In the press release at the Wits website, John Hawks has this to say about it:
“This likely adds weight to the hypothesis that Homo naledi was using dark, remote places to cache its dead,” says Hawks. “What are the odds of a second, almost identical occurrence happening by chance?”
Notice what Hawks is doing here: That's Dembski's design filter, isn't it?  There's no natural law that says hominin remains should be found in caves, so that leaves chance and design as explanations.  One large deposit of hominin remains in a cave might conceivably be there by chance (although the inaccessibility of the Dinaledi chamber argues against it), but two deposits of the same species of hominin?  Both in chambers of the same cave and extremely difficult to get into and with an age profile that looks like a graveyard?  That's low probability plus specification.  That's design.  These bodies were intentionally placed in these chambers.  Homo naledi buried their dead.

In the final paper published today, Berger and colleagues discuss the meaning of the late date of Homo naledi and argue that we cannot simply assume that tools and other signs of culture were the sole product of H. erectus, H. sapiens, or Neandertals just because they have a certain age.  With Homo naledi being so recent, there might be other hominins out there making tools or other cultural artifacts.

I'm sure I'll have more to say as I work through these papers, but for now, I have to get ready for work!

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