Sexy vampires have become so ubiquitous that we’ve stopped asking ourselves why they awaken our own sexual thirst. This mystery, however, was too compelling for science to ignore. Rather than take it as fact that the fanged monsters are just objectively attractive, a team of European researchers publishing in the journal PLOS One came up with an evolutionary theory as to why we find them so irresistible. The secret, they report, is in our reptilian past.

Looking at a fossilized skull of a pre-mammalian reptile called Choerosaurus dejageri that lived 259 million years ago, the scientists noticed something unusual: pointed “horns” — or fangs — tucked between the teeth on the skull’s upper and lower jaws. This struck them as strange because this reptile was the only one in its family, the Eutheriodontia, that had these weird protrusions. Incidentally, Eutheriodontia is part of the lineage that later gave rise to Homo sapiens — some of whom occasionally still show evidence of this fanged evolutionary past.

Something about fangs suggested “good parenting skills” to our reptilian ancestors.
Something about fangs suggested "good parenting skills" to our reptilian ancestors.

Why the presence of these weird fangs persisted throughout evolution was the real puzzle. There were two possibilities: Either they were used to an individual’s advantage during battle, or there was something about them that attracted mates. Research suggested that Choerosaurus wasn’t much of a fighter, given its weak skull and blood vessel-rich head. This latter fact, they note, suggested that Choerosaurus had a colorful “cornified structure” on its head — a kind of eye-catching hat, not unlike the feathers of a male peacock, which was probably used for seducing mates and/or intimidating others away. They conclude that the fangs on these animals probably served the same purpose.

Further evidence that fangs provided some sexual benefit to individuals that had them exist today. The fish-eating walrus or the plant-grazing, deer-like muntiac, for example, don’t exactly use their saber teeth to hunt for meat, and yet the fangs have persisted throughout evolution. Something about the long teeth in these animals and Choerosaurus must somehow have relayed the message “I’ll be a good parent!” to potential mates, and that instinct was passed down throughout evolutionary history until it manifested in True Blood-loving humans. How those fangs suggested sexual potency, however, remains a mystery, one that’s echoed in our continued, now slightly-less-puzzling fascination with fangs.