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Humans in South America

7 April 2014

At www.nytimes.com/2014/03/28/world/americas/discoveries-challenge-beliefs-… … which is a piece on discoveries at Serra da Capuara National Park in Brazil (in the NE of the country). Rock art depicts people and animals in various activities – paintings numbered in their thousands. When excavations began, in a rock shelter associated with rock art, they unearthed stone tools going back 22,000 years ago. Whilst Clovis First dominated US archaeology thinking for many years a chink has developed more recently – but they are still loathe to thinks in terms of 20,000 years ago, at the height of the last Ice Age. Down in Brazil it has become a source of pride that they have human sites older than Clovis First. Even further south than Brazil, in Uruguay, palaeontologists have published findings that say humans were hunting giant sloths there 30,000 years ago. In southern Chile, even further to the south, Tom Dillehay has shown that humans were living at a coastal site, Monte Verde, 14.800 years ago. In addition, A Brazilian evolutionary anthropologist claims that some ancient Americans resembled Australian Aborigines rather than Asians from across the Bering Strait.

Beseiged Clovis First archaeologists in the US have disputed some of these findings. One even claimed that monkeys had made the stone tools and another said they had fallen from the rock ledge above and broke to look like tools. Worked flint is easy to spot with a trained eye but stones used to pound or as a hammer are different and more difficult to identify. Most Clovis First people are hedging their bets and rely a lot on DNA evidence – seeing it as a reliable defence against the whole kit and kaboodle collapsing. They have taken heart in the recent findings that link the DNA of somebody in central Asia with a Clovis period individual in NorthAmerica and another individual from South America. In contrast, some Brazilians are claimed to have come across charcoal from a human hearth dating back 48,000 years ago – and why not. Clovis First is ingrained in US archaeology. It has become somewhat like the date of Adam, derived from counting Biblical numbers – a sort of barrier. The Brazilian archaeologists are adamant – they do not recognise an artificial time line as a barrier to their endeavours. Some of them go so far as to say humans were in South America a 100,000 years ago (the last inter glacial period). Michael Waters, a geo-archaeologist at Texas A and M University says that if the Brazilian evidence is correct they did not pass their genes on to modern populations. How can we be sure of that? Is DNA as firm as it is made out to be? There seems to be a bit of a question mark over genes being passed from ancient populations to modern ones. Take the Neanderthals – a genetically overdone debate if there is one. Only some 4 per cent of Neanderthal genes are said to survive in modern European populations – but is this a reasonable conclusion? The DNA facts speak for themselves but do ancient genes get lost at a greater rate than currently imagined. It may suit the Out of Africa people that only a small percentage of Neanderthal genes have survived. Even this is too much for those that envisage modern humans have a pristine and pure origin some how divorced from earlier humans, desperate to hang on to the myth that we are all descended from one person (who magically evolved into a modern edition of the grunts that went before). DNA research reminds me of the introduction of C14. Archaeologists, and others, suddenly had a tool that was able to date objects more precisely, it was thought, and out of the window went other dating techniques that had never been questioned before – such as lake varves, or pottery sequences. However, within 20 years it was realised that something was wrong with C14 and they tried to tidy up the dating process with calibration. The problem of course is that it was assumed C14 did not vary in the atmosphere – and likewise it is assumed they can actually date how long DNA takes to pass on changes. If they have got the sequence wrong, and old DNA is lost much faster than thought, andmore commonly, the theory will require adjustments – just like C14. The alternative would be to assume the later migrants wiped out the earlier ones. This is of course a common argument aimed at Neanderthals – it is assumed modern humans were much more advanced and the grunts were incapable of surviving because of the competition posed by the newcomers. All we really know is that Neanderthal numbers were drastically reduced between 40,000 and 30,000 years ago. One option is catastrophism – out of the question in mainstream.

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