Mammoths, and other sturdy beasts with big stomachs

26 Aug 2010

There is an unusual posting at August 24th .. on the mammoths and what they might mean for climate change. He quotes from Wikipedia which says the mammoths largely disappeared at the end of the Ice Age - and within the Ice Age, but some of them survived for a couple of thousand years into the Holocene (around 8000BC in South Siberia and shortly afterwards in North Siberia, although a small population survived on St Paul island in Alaska till 3975BC while some dwarf species lived on in the Arctic Ocean island of Wrangel Island until 1650BC). Nowadays, the island is a breeding ground for polar bears, seals, and walrus, and has been visited by human hunters for thousands of years. In the Pleistocene, the islands of the Arctic Ocean, including Wrangel and St Pauls, may have been joined to the surrounding continents. A huge spine lies underwater nowadays that virtually bridges the Arctic Ocean and this too may have been dry land. It is in fact being used by the Russians to gain sovereignty for drilling purposes - oil and gas reserves are thought to be extensive. The Americans and Canadians currently have an expedition in the Arctic Ocean looking at the geology and we may in fact learn much more about the region as a result of this.

Getting back to EM Smith (chiefio), he quotes Wikipedia again. It is estimated there are the remains of 150 million mammoth remains in Siberian permafrost - a fraction of what must have been involved as in regions to the south, mammoths are usually found as broken bones buried in sediment. He does not comment on the staggering number of bones of a species that proliferated in the Pliocene and Pleistocene - but is impressed. Frozen mammoths actually appear as the permofrost melts - very often after heavy rain. This is when collectors pick up the tusks and they are sent SE to China or find their way to Europe (and beyond). According to Wikipedia, some of the mammoth remains in the permafrost go down a kilometer deep - and is assumed to be a gradual deposition. Now, getting to the point made by EM Smith - since the Pleistocene era we have been warming, ever since those animals froze and were buried. However, mammoths being a species related to elephants, required a lot of vegetation of browsing fodder in order to thrive (which they clearly did). They must have been living where green stuff was in plentiful supply (which of course is quite unlike modern northern Siberia). Hence, it must have been warmer in that region before the mammoths were frozen - a reasonable deduction but one that is ignored by paleontologists. This is the argument he is making, mocking the idea C02 causes AGW. He is not looking at the mammoths as something peculiar (their preservation, number of carcasses, sudden nature of the event etc) but only that it must have been a warm environment in northern Siberia when they were alive. Hence, the climate was warm, it cooled and froze the mammoths, and then it warmed up again. He doesn't enquire why mammoths were deep frozen with tissue intact, sometimes complete animals only partly decomposed. If mammoths thrived in northern Siberia during the Pleistocene it must have been warmer than it is now.

Now, the Wikipedia entry on mammoths has a bibliography and after reading a few of these it becomes obvious the consensus view is that the mammoth were in all likelihood killed off by a combination of human hunters and climate change. The Younger Dryas event is heavily implicated in their demise. Most of these articles are full of wind and supposition and totally avoid the full scope of the disaster - and this is the reason why. It emerges that computer models and simulations have shown how and why they disappeared but as we all know computer models are only as good as the input. In this instance, only two possibilities have been inserted into the models, changing climate and the appearance of humans (see - Elsevier) (Burney and Flannery, South Australia Museum in Adelaide and published in Trends in Ecology and Evolution, July 2005). Obviously, if the only input is climate change and human activity, no matter how varied and diverse, you will only get them back as your answer. The idea the poles may have changed, or the axis of rotation, is completely ignored - quite apart from a catastrophe such as that hypothesised at the beginning of the Younger Dryas event (when a major extinction event occurred). Also, if the researchers ignore the scale of the extinction, the number of remains for example, how can they truthfully blame it on human hunters? Could they be responsible for 150 million carcasses in one small part of mammoth habitat?

On a similar kind of note there is a post at which refers to a study that purports to show carnivores shrank in size during a global warming event 55 million years ago (derived from a press release from the University of Florida but the research itself was published in the Journal of Mammalian Evolution). Later, when the climate cooled the carnivore appears to have evolved into a bigger size - but once again we appear to have a boundary event and therefore probably a catastrophe rather than simply a case of the planet warming up for a short period of time. Scientists have interpreted it not as a catastrophe but a period in which C02 levels increased (warming must mean higher C02 levels as that is the consensus theory) and it is speculated this must also mean a drier environment. They say they don't understand why the mammals shrank and throw in the explanation of C02 increase as reducing plant nutrients (which is quite opposite to what C02 actually does) which in turn caused herbivores to shrink - and carnivores shrank in sympathy. The comments after the post are scathing - and unrelenting. Amimals are larger the further north you go as bigger means more heat retention - even in the same species. I might add that the change in size might also reflect a change in the axis of rotation or polar wandering - especially as it occurs at a boundary event in which a large number of fossils were formed and preserved in sediments.

Whilst we are on extinct animals there is an article on the demise of cave bears in Europe at which is also interesting as these became extinct also at the end of the Pleistocene. However, there was also a large die-off of cave bears around 35,000 years ago although in Australia many large animals died out around 50,000 years ago and it seems that cave bears also declined at this point in time also - on the opposite side of the world. The connection is again made that these declines and extinctions coincided with the expansion of modern humans and the paper is published in Molecular Biology and Evolution so we can't expect a radical proposal to account for these falls in population numbers. The decline at 35,000 years ago is particularly targeted (the arrival of the Cro Magnons that superseded the Neanderthals) and is attributed to human competition for land and shelter - did the cave bears get evicted?

The story continues by saying they hibernated in limestone caves where the remains of individuals that had died previously were stacked up - thereby explained why such huge piles of cave bear remains have been found in such caves (very often mixed with the bones of other animals), and these deposits gradually accumulated over a long period of time. The idea that it may have happened suddenly, on more than one occasion, is not on the radar. We may note the date of 35,000 years ago is one chosen by Firestone, West and Warwick-Smith in The Cycle of Cosmic Catastrophes as a particularly significant event in which large numbers of animals died around the world. Many mammoth remains, for example, which indicate there was a large die-off at this time - which they suggest has a cosmic dimension.