A new study, published Wednesday in the journal Nature, reveals more on why they aren't around anymore: Dire wolves couldn't make little dire wolf litters with today's gray wolves, even if they wanted to.
"Despite anatomical similarities between gray wolves and dire wolves -- suggesting that they could perhaps be related in the same way as modern humans and Neanderthals -- our genetic results show these two species of wolf are much more like distant cousins, like humans and chimpanzees," said study co-lead author Kieren Mitchell, from the University of Adelaide in Australia. ."While ancient humans and Neanderthals appear to have interbred, as do modern gray wolves and coyotes, our genetic data provided no evidence that dire wolves interbred with any living canine species," Mitchell said.