Researchers Finally Solve Charles Darwin's Mystery

By Stuart Wolpert

When Charles Darwin visited the Falkland Islands during the voyage of the Beagle in 1835, he saw a wolf-like species, wrote about it in his diaries and correctly commented that it was being hunted in such large numbers that it would soon become extinct.

Darwin was baffled by how this animal got on the islands, and it figured heavily in the formation of his ideas on evolution by natural selection.

Now, UCLA biologists and colleagues have analyzed DNA from museum specimens, including one collected by Darwin, and have solved the puzzle. Their results surprised them.

"It was the only terrestrial mammal on the island," said Robert Wayne, UCLA professor of ecology and evolutionary biology and co-author of the research paper, published Nov. 3 in the journal Current Biology. "How can something the size of a Labrador retriever end up on an island in sufficient numbers that a new population emerges and evolves into a new species? The presence of this large canid, the Falkland Islands wolf, has always been a puzzle, since the early 1800s."

Was it brought to the Falklands, less than 300 miles from the mainland of South America, by humans or did it somehow get there by itself?

"Our analysis rules out humans," said Graham Slater, a postdoctoral scholar in the UCLA Department of Ecology and Evolutionary Biology and lead author of the paper.

Slater, Wayne and colleagues analyzed DNA samples from five Falkland Islands wolves and calculated how long ago those five wolves shared a common ancestor.

"It was at least 70,000 years ago—well before humans came to the New World," Slater said. "The Falkland Islands wolf clearly precedes any possible human occupation of the New World, which dates back some 12,000 to 13,000 years."

Darwin hypothesized that the Falkland Islands wolf, which became extinct in 1876, may have come to the islands on icebergs. Wayne and Slater think Darwin may be right.

"A large, wolf-size animal could perhaps live on a large iceberg with penguins and sea birds and maybe seals—enough prey to survive the voyage—where a vegetarian could not do that very well," Wayne said. "There is a possibility that a pack of wolf-like animals (which are members of the biological family of mammals that includes wolves, foxes, coyotes, jackals and domestic dogs) could be marooned on an iceberg that would eventually land at the shores of the Falkland Islands, then live off the sea birds and marine mammals there and give rise to a new population that over time would turn into a dramatically different species."

"If you look at Darwin's notebooks, the first time he ever raised the idea that species are not fixed entities was after he considered birds from the Galapagos Islands," Slater said. "He is talking about how they are different from island to island, and he says, 'The only other example I can think of is the wolves of the Falkland Islands.' Then, the next sentence is the first time he ever said, 'This leads me to believe that species are not fixed entities and change over time.' When Darwin first was thinking that species evolve, he had the Falkland Islands wolf in mind."

The closest relative to the Falkland Islands wolf, the biologists report, is an odd South American dog species called the maned wolf, which looks nothing like the Falklands species.

"The closet living relative of the maned wolf is the bush dog, which is even more different," Slater said. "These three are a strange group."

"That was a shock to us," Wayne said. "You wouldn't have guessed by looking at them that that the maned wolf and the bush dog could give rise to something like a Falkland Islands wolf, but we have verified it."