London, Oct 7 (udaipur kiran) The last wooly mammoths that roamed the Earth on an island in Arctic ocean died 4,000 years ago owing to isolated habitat, extreme weather events and spread of prehistoric man, say researchers.
The last woolly mammoths lived on Wrangel Island in the Arctic ocean. An international research team from the Universities of Helsinki and Tübingen and the Russian Academy of Sciences has now reconstructed the scenario that could have led to the mammoths’ extinction.
The team examined the isotope compositions of carbon, nitrogen, sulfur and strontium from a large set of mammoth bones and teeth from Northern Siberia, Alaska, the Yukon, and Wrangel Island, ranging from 40,000 to 4,000 years in age.
The results showed that Wrangel Island mammoths’ collagen carbon and nitrogen isotope compositions did not shift as the climate warmed up some 10,000 years ago.
The values remained unchanged until the mammoths disappeared, seemingly from the midst of stable, favourable living conditions.
Earlier DNA studies indicate that the Wrangel Island mammoths suffered mutations affecting their fat metabolism.
In this study, the team found an intriguing difference between the Wrangel Island mammoths and their ice age Siberian predecessors: the carbonate carbon isotope values indicated a difference in the fats and carbohydrates in the populations’ diets.
“We think this reflects the tendency of Siberian mammoths to rely on their reserves of fat to survive through the extremely harsh ice age winters, while Wrangel mammoths, living in milder conditions, simply didn’t need to”, said Dr Laura Arppe from the Finnish Museum of Natural History Luomus, University of Helsinki.
During the last ice age — some 100,000 to 15,000 years ago — mammoths were widespread in the northern hemisphere from Spain to Alaska.
Due to the global warming that began 15,000 years ago, their habitat in Northern Siberia and Alaska shrank. On Wrangel Island, some mammoths were cut off from the mainland by rising sea levels; that population survived another 7000 years.
Another possible factor for the could have been the spread of humans. The earliest archaeological evidence of humans on Wrangel Island dates to just a few hundred years after the most recent mammoth bone.
“The chance of finding evidence that humans hunted Wrangel Island mammoths is very small. Yet a human contribution to the extinction cannot be ruled out,” said the researchers in the latest edition of Quaternary Science Reviews.