France Media Agency14 août 2020 13:01:47 IS
A woolly brown rhino that weighed two tonnes once roamed northeastern Siberia before mysteriously disappearing around 14,000 years ago.
Was its disappearance caused by humans or by the global warming of the time?
A new study by a team of Swedish and Russian scientists who examined DNA fragments from the remains of 14 of these prehistoric mammals allows our species to get away with it.
They say the population of the animal – also known by its scientific name Coelodonta old – remained stable for millennia as they lived alongside humans, before dropping sharply towards the end of the last ice age.
“This makes it more likely that climate change around 14,000 years ago was the main driver of extinction, rather than humans,” said Love Dalen, geneticist at the Swedish Center for Paleogenetics. AFP.
Dalen led the study published in the journal Current biology Thursday.
How did they come to this conclusion from DNA strands taken from animal remains frozen in the ground for thousands of years?
The size of a population of a species is proportional to its level of genetic diversity and the degree of inbreeding, Dalen said.
The team was able to analyze the complete genome of a rhino dating back to 18,500 years ago.
Loading woolly rhinoceros. Image Credit: Szymon Górnicki
By comparing the chromosomes inherited from the mother and the father, they determined that inbreeding was low and diversity was high.
“An individual’s genome is a mosaic of all of their ancestors,” explained Dalen.
“18,000 years ago this rhino was part of a large population, and its ancestors must have been part of a large population too” dating back tens of thousands of years.
From other animals, they were able to harvest mitochondrial genomes – which are passed down from the mother – and from there they were able to estimate the sizes of female populations over time.
Humans arrived in this part of Siberia 30,000 years ago. Although they hunted the rhinos, the animal’s population remained stable for another 12,000 years until a sudden warming period known as the Bolling – Allerod.
The same team has previously published the genome of another megaherbivore, the woolly mammoth – and believes this species has also become extinct due to climate change, not human hunting.
Their findings are still the subject of debate within the scientific community.
One key difference is that mammoths have gone extinct twice: those in mainland Siberia went extinct around the same time as the rhinos, but a few hundred survived on Wrangel Island six millennia longer.
Today, the woolly rhino’s closest living relative is the Sumatran rhino.
Often poached and faced with the destruction of their habitat, less than 80 remain.
Here, no one can claim that humans are free from blame.
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