Homo Naledi

12 Sep 2015

At http://anthropology.net/2015/09/11/news-from-rising-star-cave-homo-naled... ... another story picked up by the media in general without a lot of thought about what was being said in the press release. The link above is an anthropology blog, and a post by one Tim Jones. On September 10th it was announced that fossil remains of a dozen individuals had been found and collected from a cave in South Africa, and the press release came with a fair bit of speculation that the media apparently lapped up without thinking much about what was being spoon fed to them. What we have is a patchwork analysis of bones that is all about interpretation in the evolutionary model rather than a discussion of potential problems. However, we may also note the discovery also upsets some consensus views on the pace and road map of human evolution.

Tim Jones points out that two issues are yet to be resolved - i) the dating of the fossils, and ii) the DNA analysis of the bones. These, I would have thought, were a little bit important.

The bones were found on a damp cave floor in a rather haphazard scatter. They were not arranged in any kind of order, as in a burial. They may even have been washed into the cave as the entrance is so narrow, just 18 inches wide in which only a very slim individual could squeeze into, and the opening even reduced to 10 inches wide (but not where the squeeze was accomplished as one would have had to have had a matchstick torso and a rubber head). Jones emphasizes the bones were not organised and did not occur in a sedimentary layer that could be dated by a geologist, even a hint of a date. Jones says this may indicate they died out fairly recently, in perhaps the same time time frame as Homo floriensis (the hobbits from a cave on the Indonesian island of Flores) which were also found in wet and muddy conditions dating back just 12,000 years ago.

It is being suggested the bones from the Rising Star cave could date back hundreds of thousands of years and even suggested the manner of their burial (deep within a cave system) may indicate deliberate burial which amounts to a human development unknown amongst homonids to date - but is this projection? According to Jones there is very little evidence to confirm these ideas.

The rising star cave bones represent humans of all ages - and the discovery was made through a narrow passage just 18 inches wide. How did the bones get through a crevice that narrow? Jones then suggests thilat rather than an ancient deposit the bones are probably  there as a result of a relatively recent incident - possibly dating to the Late Pleistocene. He suggests Homo Naledi was a relic population that had developed in southern Africa and had remained in isolation until a matter of thousands of years ago (rather than hundreds of thousands), dying out perhaps as a result of a calamitous event (a catastrophic natural disaster). The known timescale of purposeful burial is not that long ago - in western Asia it is the Neolithic period (early to middle Holocene) so it is unlikely homonids purposely deposited the bones (although that is just his view and it is not outside credibility that even homonids wished to keep the remains of loved ones in a position out of reach of scavenging animals).

Basically, he is saying the bones were not degraded enough to foil a DNA analysis - which is the odd part of the press release. It is quite possible the bones will be DNA analysed in time - so were they jumping the shark? The bones, however, were found in a waterlogged situation, which has up to now prevented such analysis - but it will be done. The results, when that happens, will be fascinating, he suggests, but until tests are done the talk of missing links is premature.