Geneticists may have just solved a 320-year-old evolutionary mysteryS

The Falkland Islands wolf is a riddle wrapped in an enigma wrapped in a tawny fur coat. For starters, it's not even a wolf (more on that in a minute); but far stranger is the fact that, when it was first encountered on the South American archipelago for which it's named, it was literally the only terrestrial mammal in sight.

For over 300 years, the origins of the now-extinct creature have remained a mystery — an evolutionary puzzle even Charles Darwin couldn't crack. Now, a team of geneticists thinks it has a definitive answer.

Back in 1834, when Darwin first encountered the canine on the Falkland Islands, he found it to be uncommonly tame, and friendly to a fault. While it's more closely related to foxes (genus Vulpes) than wolves (genus Canis), the Faulkland Islands "wolf" actually belongs to its own, now-extinct genus by the name of Dusicyon — a detail that has led to it being referred to more simply as the "warrah." Unlike its evolutionary cousins, the warrah was famously affable towards humans. When 17th century British explorers first met the warrah, they too had made note of its congenial disposition — which they promptly realized made it very easy to kill. By 1880, the warrah was extinct. Fun fact: the Latin "Dusicyon" literally translates to "foolish dog."

More puzzling to Darwin, however, was the realization that the warrah was, in fact, the Falklands' only mammal. A baffling observation, given that the islands are separated from South America's bottommost tip by almost 300 miles of ocean.

Theories on the warrah's provenance have been swirling for centuries. Some say it drifted its way to the island aboard ice or vegetation. Others posit that it arrived — already domesticated — with early human settlers. An ephemeral land-bridge, now submerged, seems a reasonable explanation, until you remember that the islands were utterly bereft of any other mammals upon the arrival of 17C Europeans. Needless to say, a dearth of definitive genetic data has made narrowing in on an answer somewhat tricky.

But now, a team led by University of Adelaide geneticist Alan Cooper may have the evidence it needs to put this riddle to rest. By comparing DNA from the skull of a warrah (collected by Darwin himself) with that of six specimens of the creature's also-extinct mainland relative, Cooper and his team have revealed that the two canines began to evolve independently from a common ancestor just 16,000 years ago — directly on the heels of the iciest period in Earth's last ice age.

Geneticists may have just solved a 320-year-old evolutionary mystery

"The Eureka moment was finding evidence of submarine terraces off the coast of Argentina," said Cooper in a statement, which he says would have formed around the time of the last glacial maxima (between 25,000 and 18,000 years ago).

"At that time," he continues, "there was a shallow and narrow (around 20km) strait between the islands and the mainland, allowing the Falkland Islands wolf to cross when the sea was frozen over, probably while pursuing marine prey like seals or penguins."

As for the absence of other furry creatures, the authors write that the distance would likely have proven too great for creatures much smaller than the warrah to traverse. "Other small mammals like rats weren't able to cross the ice," posits Cooper.

The researchers' findings are published in the latest issue of Nature Communications.

Top image by Michael Rothman; S.A. Map via Cooper et al.