Thursday, 13 August 2015

What Killed the Megafauna, Humans or Climate Change?

Reconstruction of megafauna of northern Spain.
Source: Wikipedia. Credit: Mauricio Antón
Humans responsible for demise of gigantic ancient mammals: Early humans were the dominant cause of the extinction of a variety of species of giant beasts -- ScienceDaily

A team of scientists believe they have solved the conundrum of what cause the extinction of the so-called megafauna at the end of the last Ice Age. The megafauna is the large mammals such as mammoths, wooly rhinoceroses, sabre-toothed tigers and giant armadillos all of which went extinct between 80,000 years ago and 10,000 years ago.

The debate for about the last 50 years has been whether it was humans who exterminated them, or whether climate change did it as Earth came out of the last major glacial period. Now the team from Exeter, Cambridge, Reading and Bristol Universities believe they have shown that it was humans who did the dirty deed. They believe they have found a stronger correlation between the arrival of humans and the extinction of the animals than that between climate change and extinctions. However, there were a few areas where the correlation was strong for either and where more research is needed.

Unfortunately, the original paper is behind a paywall and even the abstract is copyright protected (permission to reproduce applied for - I do wish any research which is publically financially supported would be published with open access!) [Later edit] John Wiley and Son, via Copyright Clearance Center, wanted to charge £88.36 for permission to quote the abstract to this paper. I declined their offer.

Interesting though these sorts of nice argument are, I sometimes wonder if scientists are looking for distinctions where there are none.

Although the immediate cause of extinction might well have been killings by newly-arrived humans, or maybe competition for living space, but biologically, the arrival of humans into these animals' environment was an environmental change which was almost certainly facilitated by climate change.

It doesn't need to have been the warmer weather per se, or loss of food plants, etc. which killed them off but the arrival of a predator because of the opportunities a milder climate presented to them. The underlying driver was still climate change; only the precise mechanism is open for debate. Climate change inevitably leads to environmental change, including changes in the distribution of different species. It would be astonishing if it didn't.

Biologically, the species was unable to adapt quickly enough to a rapid change in the environmental it had adapted to slowly in earlier times, and so became extinct.


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