Interbreeding is quite common among wolf lineages when their geographical ranges overlap. The dire wolf was a ‘lone wolf’ when it came to breeding “Dire wolves are sometimes portrayed as mythical creatures - giant wolves prowling bleak frozen landscapes - but reality turns out to be even more interesting,” said Kieren Mitchell of the University of Adelaide, a co-lead author. “This must mean that dire wolves were isolated in North America for a very long time to become so genetically distinct.” “When we first started this study, we thought that dire wolves were just beefed-up gray wolves, so we were surprised to learn how extremely genetically different they were, so much so that they likely could not have interbred,” said the study’s last author, Laurent Frantz, a professor at Ludwig Maximillian University and the U.K.’s Queen Mary University. The dire wolf, on the other hand, based on its genetic difference from those species, is now believed to have originated in the Americas. The ancestors of the gray wolf and the much smaller coyote evolved in Eurasia and are thought to have moved into North America less than 1.37 million years ago, relatively recently in evolutionary time. Further, we’ve shown that the dire wolf never interbred with the gray wolf,” said co-lead author Alice Mouton, who conducted the research as a UCLA postdoctoral scholar in ecology and evolutionary biology in Wayne’s laboratory. “We have found the dire wolf is not closely related to the gray wolf. The absence of any genetic transference indicates that dire wolves evolved in isolation from the Ice Age ancestors of these other species. Significantly, they found no evidence for the flow of genes between dire wolves and either North American gray wolves or coyotes. Using cutting-edge molecular approaches to analyze five dire wolf genomes from fossil bones dating back 13,000 to 50,000 years ago, the researchers were able to reconstruct the evolutionary history of the long-extinct carnivore for the first time. “Dire wolves have always been an iconic representation of the last ice age in the Americas, but what we know about their evolutionary history has been limited to what we can see from the size and shape of their bones,” said co-lead author Angela Perri of Durham University. Gray wolves, also found in the fossil-rich pits, have survived until this day. More than 4,000 dire wolves have been excavated from the La Brea Tar Pits, but scientists have known little about their evolution or the reasons for their ultimate disappearance. The Pleistocene, commonly called the Ice Age, ended roughly 11,700 years ago. “The terrifying dire wolf, a legendary symbol of Los Angeles and the La Brea Tar Pits, has earned its place among the many large, unique species that went extinct at the end of the Pleistocene epoch,” said UCLA’s Robert Wayne, a distinguished professor of ecology and evolutionary biology and the study’s co-senior author. The study, which puts to bed a mystery that biologists have pondered for more than 100 years, was led by researchers from UCLA, along with colleagues from Durham University in the U.K., Australia’s University of Adelaide and Germany’s Ludwig Maximilian University. The iconic, prehistoric dire wolf, which prowled through Los Angeles and elsewhere in the Americas over 11 millennia ago, was a distinct species from the slightly smaller gray wolf, an international team of scientists reported in the journal Nature. Two gray wolves (lower left) confront a pack of dire wolves over a bison carcass in Southwestern North America 15,000 years ago.