DNA and ancient remains suggest that most mammoths had died out around 10,000 years ago - but why did they go extinct?
Credit: Wikipedia
ADELAIDE: A new analysis of ancient mammoth DNA backs climate as the main culprit in their extinction, partially exonerating palaeolithic human hunters.
DNA extracted from the remains of woolly mammoths (Mammuthus primigenius) suggests that a trend of decreasing genetic diversity had already taken hold prior to the onslaught of human hunting, according to research revealed today in the journal Current Biology.
"A picture is emerging of extinction not as a sudden event at the end of the last ice age, but as a piecemeal process over tens of thousands of years, involving progressive loss of genetic diversity," said lead author, palaeobiologist Ian Barnes from the University of London, England.
"For the mammoth, this seems much more likely to have been driven by environmental rather than human causes, even if humans might have been responsible for killing off the small, terminal populations that were left," he added.
Extinction question
The mammoth was mostly extinct by the end of last ice age 10,000 years ago – although a small population did cling to survival on Wrangel Island, north of Siberia, until around 3,700 years ago.
The mammoth is thought to have appeared around 150,000 years ago, adapting to the frigid conditions of an earlier ice age.
Adaptations to the extreme cold included a thick, shaggy hair, small ears to reduce heat loss, and an insulating layer of fat. These relatives of Asian elephants had distinctive, curved tusks, up to five metres long, and were around three metres tall at the shoulder.
To help answer the question of why the mammoth died out, Barnes and his team studied the DNA of mammoth populations in present-day Siberia and Alaska. They sequenced samples of mammoth mitochondrial DNA – which is carried down the maternal line – from the bones, teeth and ivory of 41 individual mammoths.
The researchers were able to identify for the first time, distinct lineages of mammoths from Siberia and Alaska. Only one mammoth from Europe was analysed in this study limiting the conclusion that can be drawn from it, but the researchers suggest that there could be a third European lineage too.
Mammoths were able to reach the Americas from Asia via a Bering Strait landbridge that opened up with low sea levels during the ice age, said Barnes.
