A DNA study of one of the last mammoths, which was marooned on an island off Siberia 4,000 years ago, showed how the animals were wracked with mutations.
Defects caused by generations of inbreeding ravaged the last mammoths, marooned on Wrangel Island in the Arctic, the study showed.
The last mammoths may have seen a loss of male fertility and lower sense of smell – meaning the animals were less able to find food, according to the genome study.
Most woolly mammoths went extinct roughly 10,000 years ago amid a warming climate and widespread human hunting.
But isolated populations survived for thousands of years after that on Wrangel Island in the Arctic Ocean, with the last mammoths disappearing just 4,000 years ago.
The researchers compared the Wrangel Island mammoth’s DNA to that of two older mammoths as well as three Asian elephants, a close relative.
The researchers wrote: “Wrangel Island mammoths experienced an episode of rapid demographic decline coincident with their isolation, leading to a small population, reduced genetic diversity.”
They pinpointed a collection of genetic mutations in the Wrangel Island mammoth and synthesised these genes in the laboratory to test their functionality.
“We can activate those genes in the lab using cell culture and test whether they are functional or not. In this case not,” said evolutionary biologist Vincent Lynch of the University at Buffalo in New York, who led the study published in the journal Genome Biology and Evolution.
“Mutations happen all the time. But the population that lived on Wrangel was very small and inbred, which leads to an accumulation of mutations that are normally purged by evolution,” Mr Lynch added.
The sperm production-related mutations may have reduced fertility in an already shrinking population. The olfactory mutations may have harmed the ability to forage and to even smell the flowers that made up an important part of their diet.
“Mammoths ate a lot of flowers,” Mr Lynch said.
The Wrangel Island mammoth genome was previously mapped using well-preserved DNA from a 4,300-year-old molar.
The latest study built on previous research pointing to harmful mutations in the Wrangel Island mammoth.
With a population of just a few hundred, generations of inbreeding between related individuals triggered harmful mutations.
“It is indeed a sad thing,” Mr Lynch said. “Mammoths were literally huge and globally distributed, and this massive range was reduced to a tiny island in the Arctic Ocean before their extinction. It should be a warning about the consequences of climate change.”