Scientists still don’t know what precipitated the fall of the woolly mammoth—but they now have a clue as to how it spent its final days.
Using 45,000-year-old tissue remains from northeastern Siberia and a 4,300-year-old tooth found on Wrangel Island (which separated from Russia’s mainland 12,000 years ago), a team of experts was able to sequence two woolly mammoth’s complete genomes. Most notably, they concluded that the woolly mammoth population had already plummeted by the time Wrangel Island unhinged itself from the mainland’s icy grip. Rising sea levels, a product of the last ice age’s denouement, forced the split—and took woolly mammoths to their final resting place.
Ultimately, they likely went extinct on Wrangel Island, where inbreeding made it impossible for the species to survive. The team, led by Love Dalen of the Swedish Museum of Natural History, determined that genetic diversity in the younger mammoth from Wrangel Island was 20% lower than that of the older mammoth—and inbreeding occurred at a much higher rate.
As scientists collect more and more sequenced genomes from mammoths, they may be able to pinpoint what makes modern-day elephants such vivid genetic memories of their beastly cousins. Another new study published on bioRxiv sequenced the genomes of three Asian elephants and two woolly mammoths. They discovered that 1.4 million DNA letters differ between mammoths and elephants—which, in turn, change the DNA sequence for more than 1,600 protein-coding genes.
Here’s Ewen Callaway, writing for Nature News:
[…] several of the genes with changes unique to the mammoths were involved in setting the circadian clock, a potential adaptation to living in a world with dark winters and 24 hours of daylight in summer. Other Arctic animals such as some reindeer have similar mutations.
The mammoth genomes also contained extra copies of a gene that controls the production of fat cells and variations in genes linked to insulin signalling, which are in turn linked to diabetes and diabetes prevention. And several of the genes that differ between mammoths and elephants are involved in sensing heat and transmitting that information to the brain.
George Church, a geneticist at Harvard Medical School, is among several teams of scientists trying to insert some of these mammoth genes into Asian elephants using the new CRISPR/Cas9 technology . The creation of such cold-tolerant elephants would be an ambitious and highly controversial project—but scientists say it’s not out of the realm of possibility.
Photo credit: Tyler Ingram / Flickr (CC BY-NC 2.0)