Enlarge / An attempt to reconstruct what northern Greenland looked like about 2 million years ago. (credit: Beth Zaiken )

When once-living tissue is preserved in a cold, dry environment, fragments of its DNA can survive for hundreds of thousands of years. In fact, DNA doesn't even have to remain in tissue; we've managed to obtain DNA from the soil of previously inhabited environments. The DNA is damaged and broken into small fragments, but it's sufficient to allow DNA sequencing, telling us about the species that once lived there.

In an astonishing demonstration of how well this can work, researchers have obtained DNA from deposits that preserved in Greenland for roughly 2 million years. The deposits, however, date from a relatively warm period in Greenland's past and reveal the presence of an entire ecosystem that once inhabited the country's north coast.

A different Greenland

Over the last million years or so, the Earth's glacial cycles have had relatively short warm periods that don't reach temperatures sufficient to eliminate the major ice sheets in polar regions. But before this time, the cycles were shorter, the warm periods longer, and there were times the ice sheets underwent major retreats. Estimates are that, around this time, the minimum temperatures in northern Greenland were roughly 10° C higher than they are now.

Enlarge (credit: Karsten Möbius )

The Nobel Prize in Physiology or Medicine was awarded to a single recipient on Monday: Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology. Pääbo's work will be familiar to regular readers of these pages, as he was the driving force behind the completion of the Neanderthal and Denisovan genomes, and he has helped us understand how these lineages contributed to the genomes of modern humans. This has more to tell us about physiology and medicine than a casual glance might suggest.

Pääbo's central role in this story and his intense focus on this topic are likely to allow widespread acceptance of his sole-recipient status, despite the Nobels' long history of controversy over who gets acknowledged. But Pääbo also benefitted from being lucky enough to be in the right place at the right time, when a revolution in DNA sequencing technology provided the capabilities his ideas so sorely needed.

I briefly met Pääbo back in the 1990s when we were both working at Berkeley. He was already interested in old DNA and was working in one of the best labs for that sort of thing, run by the late Allan Wilson . PCR had been commercialized less than a decade earlier, and Wilson's lab was pushing the limits of the technique as a way of obtaining very old DNA that was a rare component of a sample that might have been in the environment for centuries or more—fragments of egg shells from the extinct moa birds made regular appearances in the lab at the time.

Enlarge (credit: Wikimedia Commons )

Of all the species that humanity has wiped off the face of the Earth, the thylacine is possibly the most tragic loss. A wolf-sized marsupial sometimes called the Tasmanian tiger, the thylacine met its end in part because the government paid its citizens a bounty for every animal killed. That end came recently enough that we have photographs and film clips of the last thylacines ending their days in zoos. Late enough that in just a few decades, countries would start writing laws to prevent other species from seeing the same fate.

On Tuesday, a company called Colossal, which has already said it wants to bring the mammoth back, is announcing a partnership with an Australian lab that it says will de-extinct the thylacine with the goal of re-introducing it into the wild. A number of features of marsupial biology make this a more realistic goal than the mammoth, although there's still a lot of work to do before we even start the debate about whether reintroducing the species is a good idea.

To find out more about the company's plans for the thylacine, we had a conversation with Colossal's founder, Ben Lamm, and the head of the lab he's partnering with, Andrew Pask.

Enlarge / An Eastern Gray Wolf is a mix of Siberian ancestry and coyote DNA. (credit: Michael Cummings )

Man's best friend was the first of many animals humans have domesticated. But there was no clear before-and-after moment where dogs were suddenly a distinct population of wolves. While some ancient skeletons are clearly dogs, there are a lot of ambiguous skeletons earlier than that. It's possible to get a sense of what happened using the genomes of modern and ancient dogs. But this analysis depends heavily on what you think the wolf populations dogs were derived from look like.

Now, researchers have generated a much clearer picture of the last 100,000 years of wolf evolution. The picture it paints is a population that remained a single unit despite being spread across continents in the Arctic, with the population sporadically refreshed from a core centered in Siberia. Many breeds of dogs seem to have been derived from a population of East Asian wolves. But others seem to have also received significant input from a Middle East population—but it's unclear whether that population was wolves or dogs.

Wolves around the north

The ability to sequence ancient DNA was essential to this new work, which involved obtaining DNA from 66 wolf skeletons that collectively span about 100,000 years of evolution, including most of the last ice age. Wolves are found in the Northern Hemisphere, and the skeletons used here tend to be closer to the Arctic (probably in part because DNA survives better in cooler climes). But they are widely distributed, with Europe, Asia, and North America represented. The researchers also included five ancient wolf genomes that others had analyzed, along with some genomes of modern wolves.