Guest essay by Eric Worrall
Our old friend Chris Turney, whose ship of fools got stuck in the ice while he was attempting to study global warming in the Antarctic, and replicate Mawson’s expedition, has published a new study which claims that Mammoths were killed by climate change.
According to Turney’s abstract;
The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. Here, we compare ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions/replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement/extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions prior to the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts.
The full study is unfortunately paywalled, but I think we get the idea.
Mammoths survived from the Pliocene epoch, around five million years ago, to around 4500 years ago – so they survived until the end of the Holocene Optimum, the peak warm period of our current interglacial, which preceded our cooler modern climate.
However, the Mammoths also survived the Eemian Interglacial, a much warmer period than today, which occurred between 130,000 and 115,000 years ago. The Mammoths survived the mid Pliocene, 3 million years ago, when temperatures were 2-3c higher than today, and sea levels were 25m higher.
So it seems likely Mammoths would have survived the comparatively feeble warmth of our Holocene, if it weren’t for humans.
History books I used to study, suggest humans built cunning traps for the megafauna they hunted. Who hasn’t seen dramatic pictures of primitive humans holding spears, surrounding some rearing colossus.
But this isn’t the full story. Primitive humans made extensive use of fire. Fire had multiple benefits; Grasslands are highly productive, in terms of food animals, more so than forests, where many of the interesting animals live up the tops of the trees, out of reach. Deliberately burning the forests on a regular basis created more grasslands. And frankly, why bother chasing big animals, risking injury and death, if you can simply set fire to the entire region, then wander over afterwards and brush the charcoal off the pre-cooked meat? Kind of a primitive version of fast food.
Turney’s abstract grudgingly acknowledges the impact of humans on megafauna. But I suspect the human influence was probably far more important than the climate influence. Otherwise, mammoths would have survived the comparatively feeble warmth of the Holocene, just as they survived much warmer past interglacials, over their long existence.