Genetic analysis of the now-extinct Falkland Islands Wolf has answered a biological riddle that caught the attention of a young Charles Darwin, and helped shape his understanding of evolution.

During his voyage aboard the HMS Beagle, Darwin observed that the wolves — like his now-famous finches — varied widely in size between different islands, suggesting that the traits of species were not immutable, but changed over time in response to their environments.

Darwin also wondered at the origins of the wolves, which were unusually small, and had reddish fur and relatively short jaws. He dubbed them foxes, and was the first of many scientists to suspect that the strange canids weren’t wolves at all. Others thought they were descended from dogs brought by the islands’ first human settlers. Indeed, not a single mammal species other than the wolf was native to the Falkland Islands, located 300 miles off the southeastern tip of South America.

In a study published Tuesday in Current Biology, researchers address these questions with a genetic analysis of five museum speci