Denisovans and others

18 November 2015
Archaeology

Robert Farrar sent in the link to www.dailymail.co.uk/sciencetech/article-3321354/The-mysterious-cousin-li… … we have a post on the Denisovans which may have been lost in a mail sack as it seems it is a bit late in coming into daylight. They also have a story on the North Sea tsunami which is old hat so may be somebody has been catching up and has got to the bottom of his pile of papers. The finger bone of a new human group that has become known as the Denisovans was discovered a few years ago in a Siberian cave, a sister species of Neanderthals (mainly because they were abroad and extent at the same time) and of Homo sapiens (as genetic material of the Denisovan genome has been found across a large area of Asia – especially in the east and south east. Denisovans hybridised with modern humans at some stage – presumably, or that is the inference, around 40,000 years ago. In other words, they disappeared at the same time as the Neanderthals (who were also present in the same Siberian cave). What all this is actually telling us will be reviewed over the course of time but the presence of Denisovans in the east and Neanderthals in the west (both meeting in the middle) has, it seems, eliminated Homo erectus as a remnant that survived down to 40,000 years ago – which is convenient as Homo erectus evolved over a million years prior to the appearance of the Denisovans (and his stone tools don't seem to have developed much in that long period of time). While we may wonder if a million years was really involved, a period in which Acheulian stone tools (designed to lob or throw at prey, and possessing some quite clever aerodynamic elements in the design including the ability to rotate in flight and always land point downwards) were all remarkably similar and faithfully copied over generations – and more. As a result of this supposed block in the minds of Homo erectus, unable to come up with a new design to better the Acheulian model, they are regarded as fairly backward – but if a design model works why change it. Have wooodworking tools and lathes changed much over the past several thousand years? No. The designs work and are reproduced – and the same must be true of the Acheulian design. It brought down prey, was weighted perfectly, and required a skill level that took a long time to imitate. We can therefore regard the discovery of the Denisovans as a convenience for anthropologists as it is able to by-pass what had become problematical to them – an inconvenient progression from Homo erectus to Homo sapiens.

The same story can be found at various sources including www.cbc.ca/news/technology/denisovan-molars-1.3318432 … where we learn that modern humans such as the Papua New Guinea indigenous people and Australian Aborigines have around 5 per cent of the genes of the Denisovans – and even people living in eastern Asia possess a trace of the Denisova genome, and Native Americans. The latter raises some interesting questions better left for another day but it does show that Aborigines and Melanesians in general need not have moved Out of Africa in the last 50,000 years, an incredibly short time in any case, and actually lends weight to some of the ideas of RA Fonda as explored in a post a couple of weeks ago. One gets the feeling that anthropologists in general are loathe to rock the consensus boat – but evidence, if it accrues, may change this close huddle. Exciting times in so many science disciplines. It's been too easy to collate information and compartmentalise it. Once in its box it's hard to rearrange – and museums have lots of boxes and sliding drawers in which they store their specimens etc. The cbc and the mail piece both emphasize that Denisovans display lots of genetic diversity – as the Neanderthals.

Meanwhile, at http://phys.org/print366870967.html (see also http://archaeologynewsnetwork.blogspot.co.uk Nov 16th) … other scientists have been looking at ancient genomes too, human remains from the Late Palaeolithic period (and their survival after the end of the Ice Age). It is now observed there were four strands to the make-up of European DNA (see earlier posts on the first three of them). Geneticists claim to have isolated a fourth group, people that had found a refuge from the Late Glacial Maximum by migrating into the Caucasus mountains. After the LGM (between 16000 and 13000 years ago) they moved out of this refuge into the steppe zone where they appear to have become hybridised with another dominant group of people that went on to migrate into Europe from 5000 years ago (and presumably in waves thereafter). This new group, prior to isolation, had hybridised with others living in western Asia (who went on to become the early farmers of the Fertile Crescent, migrating into the Balkans around 8000 years ago (and to Greece and the Aegean a little earlier). Hence, the reason they have not been defined previously is because they share genetic material with the early farmers. They have been accorded the name Yamnaya. However, the article then speaks of movements into India and elsewhere in southern Asia which involved one or more groups of these people, migrations that appear to pre-empt migrations of the historical period. Did they happen more than once – which is a distinct possiblity. However, if the genetic signature is clear enough to be readily seen amongst modern human DNA one is left wondering if the genetic evidence is as old as claimed. After all, a day or so ago we had news of a migration out of western Asia and Anatolia that had affected a quarter of the genome of modern Africans, and this took place just 3000 years ago.

 

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