Yet more news from the world of genetics as researchers reveal what happened to the mammoth, and when…
The woolly mammoth has long been a symbol of the complex relationship between humans and Ice Age big-game. Mammuthus primigenius, like other once abundant ‘megafauna’ such as steppe bison, wild horses, and the wild rhinoceros became extinct as the world warmed. What caused this extinction, when mammoth had survived successfully through major climatic shifts for five million years? Why did they rapidly become extinct after so many millennia? Was it climate change? Or was it bands of rapacious human hunters that caused them to vanish?
The debate has gone back and forth for a century or more, hampered by a lack of truly definitive evidence about the extinction. Now the research dynamic has changed in the face of a large-scale, metagenomic study of the DNA of 1500 Arctic plants.
The researchers examined 1541 contemporary plant genomes, also 535 permafrost and lake sediment samples from across the Arctic from the past 50,000 years. They found that a relatively homogeneous, arid, steppe-tundra vegetation mantled much of the Arctic during the last glacial maximum. Once warming began, the vegetational cover diversified dramatically. After about 9,700 BC, the open steppe tundra gave way to trees and shrubs as rainfall increased. A wetter environment with a higher proportion of moisture-loving plants tended to restrict animal distributions.
The genome data reveal that mammoth survived in northeast Siberia until about 5,300B C and in North America until about 6,600 BC. But mammoth samples from the Taimyr Peninsula in north-central Siberia show that the great beasts flourished as late as 1,900 BC (!), perhaps because the steppe-tundra survived there. These dates are far later than the estimates from skeletons, which are about 8,700 BC in Siberia and about 11,800 BC in Alaska.
The Taimyr mammoth dates tell us that humans and mammoths co-existed with one another for at least 20,000 years. This contrasts dramatically with the theory that a human blitzkrieg, in the late Ice Age, caused mammoths to become extinct. Most likely, extinction occurred when the last enclaves of steppe-tundra vanished in the face of warmer and wetter climatic conditions.
Image: Model of a woolly mammoth from the Royal British Columbia Museum
Photo: Thomas Quine