The Daily Galaxy March 25th (www.dailygalaxy.com) has a story that was also featured on Science News (www.sciencenews.org/view/generic/id/57573 ) a day or so earlier. Mitochondrial DNA analysis of a finger bone found in a cave high in the Altai mountians of southern Siberia suggests a group of unknown hominids ventured out of Africa less than a million years ago. Why? The paper is published in Nature March 24th but the finger bone, which may be significant, dates between 48 and 30 thousand years ago, in that uncertain area of C14 dating that marks it’s upper limits of reliability. The cave has previously shown that Neaderthals, and then modern humans, also lived nearby – as early as 125,000 years ago. While retrieving DNA from presumed Neanderthal fossils the unusual mtDNA was found. This indicated the mother, or the person owning the finger bone, came from an as yet unrecognised early human species. Anthropologists commenting on the find take either a sceptical view or are enthusiastic but as the date of the find happens to coincide, or not too far in distance from, the 40 to 30 thousand year marker that also witnessed the sudden disappearance of Neanderthals, we can expect some more information to be sought as this particular period of time is very interesting. Firestone et al in his book suggested a major catastrophic event in this window of time which included the killing of many large mammals around the world.
BBC News March 26th gave some update on the story, mainly some comments from Chris Stringer from the London Kensington Natural History Museum (and author of Homo Brittanicus). He said it was an exciting development. However, it emerges that together with the finger bone there was a bracelet and several other elements normally associated with modern human archaeology. Chris Stringer was not deterred and suggested ways such things might have got mixed up in the digging process. He also aired the possibility the new species may be related to Homo heidelbergensis as there is some enigmatic fossils from between 250 and 650 thousand years ago from India and China that have not yet been explained – or classified. They might just tie in with this new discovery.
On a similar subject see also www.npr.org (id124906102) we have Christopher Joyce on ‘Did Climate Change Drive Human Evolution?’ which is research a little more down to earth than the above hypothesis. Evolutionary scientists plan a new project in order to look back in time to find out how climate change in the past, over millions of years, might have affected human evolution – one of funding spin-offs from the AGW agenda that prove rewarding. Rick Potts, head of the Human Origins department at the Smithsonean Museum of Natural History has been urging such a programme for several years. The explanation accepted so far is that humans developed on the African savannah in a warm environment yet humans apparently were able to cope with the Ice Age in Europe – so they are clearly versatile. Habitats change and humans adapt. Climate changes and habitats change – centuries of drought might be followed by a shift to heavy monsoon rainfall. Frozen zones became temperate, people came or left – or stayed and adapted. Potts then asks, how did humans become adaptable? It is not quite the same thing Darwin foresaw and in a way is the same question posed in yesterday’s post about grasshoppers having the ability to change colour when their environment changed. For example, taking a black colouration in the aftermath of fire and therefore adapting to a burn landscape and avoiding the keen eyes of foraging birds, is not strictly species evolution – and this is the kind of adaptation that happened with humans too. Potts proposes that it was sudden and dramatic climate change that sparked evolutionary adaptations or even genuine evolutionary physical change. This would have included the invention of new technology in tools or even a bigger brain, better traits for walking, talking, strength etc. The plan is to get a full climate history in locations associated with early humans – in East Africa for example where there are fossil lakes with sediments that can be read like the page of a book or like the rings of a tree. In turn, climate timelines can be compared with the fossil record of animals and humans. For example, the Pleistocene extinctions are one area to home in on, he says. The extermination of large mammals in the Late Pleistocene era is often attributed to human hunting activity. Tom Gilbert, a geneticist at the University of Copenhagen does not think this is the case. He blames climate change. This development is extremely important as when climate change is mapped it can be dated and correlations with Pleistocene extinctions should be discovered – but what caused that climate change will have to be decided somewhat later.
Coeval with this subject is a new article available to download in pdf format (2 page abstract) from Cosmic Tusk, the web site of George Howard (http://cosmictusk.com ). The article comes from Geology April 2010, Anders E Carlson, ‘What caused the Younger Dryas Event?’. The YD event caused a cooling in the North Atlantic region and a weakening of the northern hemisphere monsoon. The reduction in northern heat transport warmed the southern hemisphere due to a process commonly referred to as the bipolar seesaw (Clark et al 2002). On page 355 of this issue of Geology Melott et al (2010) present an assessment of the effect a comet would have had on atmospheric nitrate as well as estimating atmospheric ammonium levels in order to provide a test for the possibility of a bolide at the outset of YD. They begin by simulating the atmospheric changes caused by the 1908 Tunguska bolide and this appears to agree with the idea as nitrate increase can be observed in GISP 2 ice cores. Scaling the predicted nitrate changes upward by 6 orders of magnitude to the suggested size of the YD bolide (that much bigger) requires a very large increase in atmospheric nitrate that was not forthcoming. Greenland ice cores do show an increase in ammonium at the Tunguska and YD boundary events but there is too much ammonium the authors say. They suggest that under high pressure nitrogen and hydrogen can form ammonium which accounts for it’s increase at the Tunguska event but not enough at the YD boundary. However, they also say the GISP2 3.5 year sample resolution might potentially dilute the levels of nitrate and ammonia increase (in just one of those years) as both compounds have short atmospheric residence times. Higher resolution sampling of the ice cores might resolve the issue it is suggested.