Chemical compounds from the mammoths’ tusks hold evidence that over a 30,000-years period – as a response to predation – the animals evolved to reach adulthood a lot earlier.
Palaeontologists have long debated the reason that led to the extinction of the Siberian woolly mammoth. Experts questioned whether human activity (hunting), climate change, or both of these factors combined were at fault.
Michael Cherney, a doctoral student at the University of Michigan, and Dan Fisher, director of the Museum of Palaeontology at the University of Michigan, took chemical samples from mammoth tusks that were about 10,000 to 40,000 years old. After examining the samples, they found that the maturation process of the mammoths had accelerated over the years.
Other studies suggested that the mammoth extinction at the end of the Pleistocene Epoch (spanned from 2,588,000 to 11,700 years ago) was due to some large-scale warming events.
However, Fisher and Cherney believe that climate change would have lead to nutritional stress, which in turn would have caused the mammoths to mature slower. The results of their analysis show otherwise: the mammoths had an accelerate maturation rate, which is an evolutionary response to predation.
“Age of final weaning is a life-history landmark that is expected to change differently in response to predation and climate-related nutritional stress,” Cherney said Tuesday at the Society of Vertebrate Palaeontology meeting in Dallas.
In their study, Cherney and Fisher looked at chemical compounds found in the tusks of fifteen young woolly mammoths. Using computer tomography scans (CT scans) of the tusk samples, the researchers were able to extract the chemical compounds.
Fisher explained that the body tissue of an infant mammoth, whose meal usually consisted of milk, would have had a different composition, than that of older mammoths. The tusks also form a new layer each day, containing chemicals that indicate the animal’s condition and diet, Fisher added.
The findings show that over the course of 30,000 years, the rate at which the mammoths reached adulthood accelerated from an average of eight years to about five years.
Perhaps over-hunting had a much more negative effect on the mammoth population, than climate change. It seems as though humans represented the primary factor in the extinction of the Siberian woolly mammoth, the researchers said.
Image Source: nationalgeographic