We're closer to cloning the woolly mammoth back into existence than ever before: Researchers have just finished mapping the complete genome of two individuals of the lost species.
"This discovery means that recreating extinct species is a much more real possibility, one we could in theory realize within decades," said Hendrik Poinar, director of the Ancient DNA Centre at McMaster University, in a statement.
Poinar's study, which appears today in Current Biology, details the complete genetic reconstruction of two woolly mammoths that lived in the frozen tundra of Siberia and northern Russia 40,000 years apart. The achievement not only has major implications for our ability to "de-extinct" long-lost mammoths, it offers new insights into the mammoth's evolutionary history and the circumstances that led to its extinction at the close of the last Ice Age.
"With a complete genome and this kind of data, we can now begin to understand what made a mammoth a mammoth—when compared to an elephant—and some of the underlying causes of their extinction, which is an exceptionally difficult and complex puzzle to solve," Poinar said.
Related: Watch Motherboard's doc on the cloning of the woolly mammoth.
Two decades ago, reviving a woolly mammoth sounded like pure science fiction. But with recent advances in synthetic biology, bringing back extinct organisms, from passenger pigeons to Pleistocene megafauna, has marched squarely into the realm of the scientifically plausible. Indeed, in 2009, the mountain goat species Pyrenean ibex became the very first extinct organism to have a live clone borne into the world, although the baby goat died from lung defects shortly thereafter.
But before any animal can be cloned back to life, its genetic blueprints need to be reconstructed. For long-extinct creatures like mammoths, this means finding tissue samples in a state of excellent preservation. Even cells that have been frozen since the animal's death will have experienced DNA degradation over time, and scientists are inevitably faced with the task of stitching the entire genome back together from fragments. (You can think of this like piecing a book together from many different partial translations.) It's a slow and laborious process, but in the past decade, the increased throughput and decreased cost of DNA sequencing technology has made paleogenomic reconstruction possible.
"If you combine the fact that our ability to get it [ancient DNA] out, our ability to repair those fragments, and the throughput of our machines is much better than it used to be, we can actually push much deeper than we could in the past, and get more complete genomes of extinct animals than ever before," Poinar said in a video interview.
Poinar and his colleagues' work underscores just how far this technology has come. In 2006, Poinar and his team mapped the first partial mammoth genome, using DNA extracted from carcasses found in the the permafrost of Yukon and Siberia. The two mammoths in the present study, a 45,000-year-old young male specimen from northeastern Siberia, and a 4,300-year-old male specimen from Russia's Wrangle Island, are the very first Pleistocene elephants to have high-quality versions of their genomes reconstructed to entirety.
"The first part of de-extinction is to have a blueprint of the organism you're interested in," Poinar continued. "What this does is provide that distinct blueprint."
Aside from offering would-be mammoth cloners the best instruction book to date, the new genomes are lending new insights into ancient history of the cold-weather elephants that once stomped across Eurasia and North America. For one, comparative analysis of the two genomes suggests that mammoth populations suffered a major setback some 250 to 300 thousand years ago, long before either individual was alive.
"It turns out when you look at these chromosomal data, you see indications that mammoths fluctuated up and down in the past," Poinar said. "This shows that these animals were much more resilient than we give them credit for."
The population decline that eventually spelled doom for the species wouldn't come until much later, at the close of the last Ice Age some 12,000 years ago. We can see traces of this event written into the genetic code of the 4,300 year old specimen, presumably one of the last mammoths to ever have walked the Earth. This mammoth's relatives probably became trapped on its Arctic island by a warming climate and rising sea levels, slowly petering out over centuries to come.
"We found that the genome from one of the world's last mammoths displayed low genetic variation and a signature consistent with inbreeding, likely due to the small number of mammoths that managed to survive on Wrangel Island during the last 5,000 years of the species' existence," said study co-author Love Dalén in the press release.
It's a bit bleak to picture the very last members of this incredible species living out their final days on a chilly island at the end of the world while the Egyptians were building pyramids. But it's incredible to consider that all these thousands of years, a detailed account of their story has been lying there, preserved inside their cells, waiting for scientists to come along and decode it.
As for Poinar and his team, they're already working on cracking the genomes of other ancient elephants, including mastodons and the Columbian mammoths of North America. Clearly, our understanding of these how these lost giants lived their lives is going to become far richer over the coming years.