Chris Stringer of the Natural History Museum in Kensington is at loggerheads with Spanish fellow palaeontologists over the dating of human fossils at Atapuerco in northern Spain – see the controversy as reported in The Observer at www.guardian.co.uk/science/2012/jun/10/fossil-dating-row-sima-huesos-spa…
The so called Pit of Bones is a subterranean chamber at the bottom of a 50 feet deep shaft within the Atapuerco cave complex. Stringer, in the journal Evolutionary Anthropology, says the Spanish team have misdated the fossils. They cannot be 600,000 years of age – no more than 400,000 years. This is the consensus view on when Neanderthals first emerged – differentiating them from Homo erectus. However, the Spanish team have designated the fossils Homo heidelbergensis, a sort of cross between the two, allowing them more elasticity in interpretation. What is even more controversial however is the claim from the Spanish team as to how these bones got to the bottom of the shaft. Now, one would have thought they were flushed down their by a rush of water entering the cave system, but no. they are saying they were thrown deliberately into the hole 'out of reverence for the dead', a sort of very early funeral and burial practise.
The dating controversy is not simple as it involves a stalagmite that appears to have grown above the sediment in which the bones were found – and the date is presumably based on uniformitarian ideas on how long it takes such a stalagmite to grow. Stringer argues that some body parts are missing – such as finger and toe bones. Another researcher chipped in by noting that is just the kind of thing one would expect if they had been swept along by a flood of water and dumped unceremoniously down a shaft. Therefore we have three points of view here from three different angles. See also http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/2885663.stm
Meanwhile, The Times 'Eureka' supplement, issue 33 June 2012, illustrates the amount of guesswork involved as far as human origins are concerned – and let us not forget whole reams of words have been strung together based on a few fossil human bones. Basically, a framework has been devised which is gradualist in concept. The idea of rapid and quick bursts of evolution is generally absent – but triggers to set in motion are a necessity. As with a lot of other disciplines it seems that Milankovitch and wobbles in the rotation of the earth over thousands of years have proved to be useful in fitting the pieces into a cohesive structure of some kind. On this occasion, the latest research, a variation on previous ideas, has begun by assuming i) that East Africa, and the Rift Valley in particular, was the cradle of humanity, and ii) that stress as a result of aridity was a major reason why humans got up off their hands and knees and became bipedal (apes) and even better, developed as big brain creatures. In this instance we are going back millions of years into the past – rather than thousands. East Africa had a warm humid climate and was fairly flattish – it is claimed. However, when India crashed into Asia and the Himalayas started to build there was likewise a lot of tectonic activity going on in Africa. The rifting began in Ethiopia and the crust split open producing a deep valley with mountains on either side. Going back to 1995, Peter deMenocle, in a study of dust levels in ocean sediments found that NW Africa, NE Africa and Arabia all became drier and dustier at particular intervals during the past few million years – namely, they became dusty. Now, that assumes the dust has an origin in an arid environment than for example an extraterrestrial dusting event, or any other origin, but the idea of switching climate regimes, from wet forest to arid desert, is not altogether unlikely. In northern Europe, and northern Asia too, climate also switched dramatically and on many occasions, but from near polar to temperate (the so called Ice Ages). So, did the switching climate in East Africa coincide with the switching climate elsewhere around the globe – that is the big question and apparently not confirmed, as yet, or repudiated in a convincing fashion. The thrust of the Times supplement article is that bipedalism, firstly, and the development of a big brain, were evolutionary traits that came about as a result of stress – during the arid phases. We don't actually see this happening in modern deserts and why didn't they simply move in tandem with the climate – following the rain that was presumably falling further south than it had been. The answer, of course, is that the aridity is thought not to be regional but global in scope – and the whole world became hotter and drier and dustier. This is taking the evidence of deMenocle a stage further – but not necessarily a stage too far. What they have found, basically, is that in cool periods of global climate there was more rain and a series of deep large lakes developed in East Africa, and during the arid phases these dried up – much as they are today. This in turn, it is alleged, is connected with the Walker east-west circulation pattern, but more commonly known from solar cycles of 60 years (one cycle of 30 years being dominated by El Nino and the other 30 years dominated by La Nina events). So, we have a small cycle that is expanded into a cycle over hundreds of thousands of year that controls El Nino, the monsoon rains, and the tropical rainfall belt – all influenced by Milankovitch cycles. In other words, climate change is elevated into being the trigger of evolution.