Death By DNA

Scientists have been studying the extinction of the woolly mammoth — those colossal, fur-covered, elephantine creatures that thrived during the last Ice Age.  And, specifically, the studies have been looking at the role genetics played in the demise of the shaggy giants with the huge, curved tusks.

example-museum-replica-species-canadian-de-extinctionThe last woolly mammoths died surprisingly recently — about 4,000 years ago, during the Old Kingdom period in Egypt.  By that time, the mammoths had vanished from the European and Asian continents due to habitat change due to global warming and the efforts of human hunters.  The last of the species lived, and died, on Wrangel Island, in the Arctic Ocean north of Russia.

According to scientists, declining numbers put the mammoths on a death spiral caused by inbreeding and genetic mutations that the population was too small to overcome.  With a shrinking pool of mates, and a lack of genetic diversity, the harmful mutations multiplied, affecting male fertility, the mammoths’ sense of smell, and other important functions.  Scientists confirmed this by taking mammoth genes from the Wrangel Island population and placing them in the cells of the mammoths’ nearest living relative, the Asian elephant, to see how they performed.  The tests showed that the mammoth genes were pitiful and failing.  The scientists also compared the genes of the last mammoths with genes from mammoths that existed thousands of years earlier, when vast herds of mammoths thrived during the height of the Ice Age.  The comparison showed that the last mammoths had an “accumulation of detrimental mutations … consistent with genomic meltdown.”

We can’t do anything for the last mammoths that perished on the frozen wastes of Wrangel Island, but their fate shows what happens when the population of a species simply becomes too small to overcome genetic mutations.  It’s a cautionary tale to keep in mind as we look to identify, and protect, the endangered species currently inhabiting planet Earth.

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