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DNA Analysis Reveals the Role of Climate Change in Mammoth Extinction

Pleistocene megafauna could handle cooling periods, but global warming was another story.
July 26, 2015, 9:22pm

Over the past few years, advances in ancient DNA extraction have fueled a lot of debate over whether scientists can—or should—resurrect the woolly mammoth from extinction. Interestingly enough, these very same advances have simultaneously shed light on what edged out mammoths out at the tail end of the last glacial period some 10,000 years ago.

Human activity has long been indicted in the extinction of Pleistocene megafauna (animals weighing over 45 kilograms, or about 100 pounds). But according to a comprehensive new study published this week in Science, the most dominant factor in the fall of these massive animals wasn't over-hunting or habitat encroachment. It was climate change, specifically global warming.

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Indeed, the authors of the study, led by paleogenetics specialist Alan Cooper, note that periods of global cooling did little to affect Pleistocene ecosystems, while warming periods disrupted them completely.

"We compare[d] 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," the team writes.

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"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 paper continues.

In other words, lining up 56,000 years worth of climate data alongside genetic transitions in the fossil record exposed a clear correlation between periods of global warming and mass population upheaval in megafauna.

There's no doubt that human activity still contributed to the decline of these large animals by placing additional environmental pressures on them. But Cooper's team cited many examples of climate-change-driven extinction that occurred in the absence of any human activity, while also pointing out that "several taxa (e.g., mammoth) go extinct on the mainland of Eurasia considerably later than that of the New World, despite a much longer exposure to human hunting."

As co-author Chris Turney put it, "the abrupt warming of the climate caused massive changes to the environment that set the extinction events in motion, but the rise of humans applied the coup de grâce to a population that was already under stress."

The team's findings provide yet another wakeup call about the disastrous ecological consequences of climate change, especially global warming. "Even without the presence of humans we saw mass extinctions," said Cooper in a statement. "When you add the modern addition of human pressures and fragmenting of the environment to the rapid changes brought by global warming, it raises serious concerns about the future of our environment."

In other words, before scientists commit to reviving these long-dead creatures from extinction, it's worth considering whether we can offer them—or ourselves—a safe, stable habitat for the future.