Follow
Mammoth tusks have a story to tell and its end is not pretty: woolly mammoths are gone and we are to blame. A recent study points the finger at reckless hunting rather than global warming in woolly mammoth extinction.
Past studies had shown that woolly mammoths went extinct because of natural global warming at the end of the last glacial period, reckless hunting or both. But although there are dozens of studies on the issue, the problem has yet to be resolved.
But a team of researchers from the University of Michigan argue that chemical hints in baby mammoth tusks may hold the key to the issue. Scientists reported that an isotopic signature in tusks revealed that the weaning age in mammoth populations steadily decreased by about three years before the ice-age pachyderms went extinct.
Weaning age marks the time when a baby animal stops nursing. While changes brought by global warming in animals’ nutrition delay weaning ages including those in modern day elephants, predatory pressure forces animals to reach adulthood faster and decrease weaning age.
Michael Cherney, one of the co-authors of the study, argued that earlier weaning is a clear sign that mammoth extinction was not caused by climate change, but by increased pressure from human hunters. Other ice-age mammals might have shared a similar fate, but more research needs to be done, researchers added.
Nevertheless, study authors acknowledged that their findings were not a final answer to explain mammoth demise. But they hope that the new theory may put the issue in a different perspective and help scientists find new approaches to unlock the mystery.
In their study, researchers analyzed a private collection of dozens of Siberian mammoth tusks. The collection includes more than 30 baby mammoth tusks. Russian authorities gave their approval to the collection and exportation of the tusks.
Daniel Fisher, another University of Michigan involved in the study, explained that the scientists had known for decades that weaning age may be learned from chemical information in tusks. But the recent study is the first to find compelling evidence of early weaning in such a wide range of geological ages, Fisher also said.
Study authors base their findings on 15 tusks from woolly mammoths with ages ranging from three to 12 years old. Tusks’ lengths ranged from 10 inches to 30 inches long. Researchers also studied elephant calves to learn what type of isotopic signature early weaning was tied to.
They learned that as solid food was introduced into the animals’ diets, the nitrogen-15 to nitrogen-14 ratio decreased. The team found increasingly lower nitrogen 15 levels in mammoth tusks, which suggests that milk was reduced earlier from overall diet.
Image Source: Wikimedia
