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pinning down the mammoths

12 August 2015

At www.livescience.com/9771-mamm oths-alive-thought.html …. it seems mammoths may not have gone extinct in the Late Pleistocene (Younger Dryas Boundary) after all. Pockets of them may have survived in ecologically favourable areas of Alaska – and elsewhere (according to DNA extracted from frozen soil in permafrost).

The DNA of horses (that also went extinct in N America) as well as mammoth was locked in an ice and frozen soil – so how  did these herbivores survive?

The Late Pleistocene date is derived from dating bones and teeth of the animals using radiocarbon methodology (but also going by the dating of the geology they were embedded within). The researchers claim they set out to test this theory by looking at how frozen sediments have been used in northern Siberia and Canada. This frozen soil is known to contain small fragments of animal and plant DNA, exceptionally well preserved. Both C14 and optically stimulated luminescence were used to date plant and animal remains from the Alaskan permafrost and individual mineral grains found in the same layer as the DNA. They say therefore they are confident the sediment deposit has not been contaminated.

The core sample recorded the local Alaskan fauna at around 11,000 years ago – and it was similar to modern mammal life such as Arctic hare, bison and moose. However, the cored sample dated between 10,500 and 7600 years ago confirmed the present of mammoth and horse – so what are we to make of it?

The authors of the PNAS research study visualise a small population of these animals survived – which is not unreasonable in the case of a small niche population in a desirable valley location. However, we may also wonder why they died out when they did, just as the Mid Holocene Warm Period went into full steam. There appears to be two explanations worth thinking about – and both involve the major event dated 8200-8000 years ago. Did the final herds die out as a result of catastrophism at this time or were the sediments mixed by the same catastrophic event (and they really did die out at the Younger Dryas Boundary event). We shall have to keep an eye out for how their fellow scientists interpret the findings – but the evidence seems, on the face of it, pretty strong.

PS … note that 8000 years ago comes well within the time limits of the sample, 10,500 to 7600 years ago.

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