Wednesday, March 17, 2010

a complex picture emerges?

Homo georgicus? I think I should start collecting skulls. 

Now let's move out of Northern Spain and the Iberian peninsula to a Lower Paleolithic open air site in Thuringia in eastern Germany. The site is called Bilzingsleben and the finds there date from 320 to 412 kya.

The place appears to have been a camp site. More than 200,000 'silex artefacts' [basically flaked stone] have been found there, as well as pebble and bone tools, the bones of hunted animals, and some engravings on bone. Human remains have been generally labelled as late H erectus, or H heidelbergensis.

The engravings, which provide evidence of art from a remarkably early period, have naturally caused quite a stir in palaeontological circles. Mind you, in this diverse field, all sorts of claims are made. Here, for example, we find talk, loose or otherwise, of art during the Oldowan era, which goes back 2.6 million years. By the way, I must get these 'eras' straighter in my mind and in my blog. Later.

On to other sites. At this stage I'm looking at European sites, but I want to summarize the most important Asian and African sites too. My mini-researches on the net have revealed often vicious disputes about the territory inhabited by H neanderthelensis, H erectus, H ergaster and other putative versions of Homo, about when they flourished and how 'advanced' they were. So many people have their pet theories. I don't know what my pet theory is – hopefully I don't have one. However, not having one does lead to a certain confusion at times, when faced with contradictory claims. It's a matter of having your bullshit antenna well primed, but also of having to take much on trust, more or less of necessity. Hopefully, a picture of the 'true' state of affairs, ever shifting and reforming, will begin to emerge.

Chilhac, a karst cave in the Massif Central region of France, is a controversial site, once considered to have produced evidence of human habitation – probably H erectus, and dating back more than a million years. However, there now seems to be evidence that what were once thought to be artefacts found at the site are in fact naturally occurring phenomena. They're probably pseudo-artefacts [cf the paper 'Tephrofacts and the first human occupation of the French Massif Central' by Raynal et al].

Dmanisi in Georgia is a Lower Paleolithic site featuring four hominid fossils. It's situated between the Black Sea and the Caspian, between Europe and Asia you might say, and was discovered quite recently, in 1983. The first human fossil, discovered in 1991, was dated at 1.7 million years. The find no doubt confounded the out of Africa theories of the time. This site says the fossil was found 'together with stone tools', but as far as I know, stone tools only go back 800,000 years or so.

Oops, completely wrong about that. The august Archaeological Institute of America [well it sounds august] declares here that the oldest stone tools thus far found, in the Afar region of Ethiopia in the early nineties, are between 2.5 and 2.6 million years old. I think the other date was for the first stone tools found in Europe. The Dmanisi site would be better categorised as Asian than European.

These tools, known as the Gona artifacts because they were found on the dry bed of Ethiopia's Gona River, have not been directly associated with proto-human fossils. They predate the Homo genus by half a million years and are taken as evidence that the Australopithecines were also toolmakers.

Getting back to Dmanisi, I don't know if this provides evidence of the first hominid out of Africa. The human fossils found there are generally identified as Homo erectus or Homo ergaster [these may be the same species, identified with Asia and Africa respectively]. More recently, the human fossils of Dmanisi were given a new [tentative as ever] species name, H georgicus, These remains have been posited as descended from H habilis and ancestral to Asian H erectus. Confusing, isn't it?

I of course hardly know what I'm talking about but this site provides as good a starting place as any for the kind of story I'm failing to tell. It suggests well the fluidity of the classifications being used, the paucity of information upon which tentative species determinations are made and so on. It also makes clear – assuming it's true of course – that the out of Africa scenario argued for, the one that prompted all this writing from me, is a scenario relating only to our sole surviving species or subspecies. Yes, our genetic ancestors seem to have come out of Africa about 70 kya, but there were plenty of hominids already in the worlds to which we spread – particularly H erectus in Asia and H neanderthalensis in Europe. In fact, the out of Africa model is sometimes called the 'complete replacement model'.

These earlier hominids may also have escaped from Africa earlier, by means of the Sahara pump as it has been called, that's to say periods of wetness and greenness in the Sahara which have been like a pump or a pipeline to the north and the east. And there's still an alternative hypothesis, not quite dead yet, called the multiregional model, which would look to a kind of world-wide, more or less uniform evolution with local variants that aren't sufficiently great to amount to speciation. However, the genetic evidence, which I can't judge, tends to confirm the out of Africa model.

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