Sex had to start somewhere. And according to a new paper in the journal Nature, that somewhere was Scotland, about 385 million years ago.

A new look at fossils of a fish called Microbrachius dicki indicates that it was the first species to reproduce not through spawning—in which the female and male release eggs and sperm separately—but through mating with each other. Lead author Professor John Long, from Flinders University in Australia, told BBC News, "We have defined the very point in evolution where the origin of internal fertilization in all animals began."

A previously unnoticed L-shaped appendage on fossils of M. dicki proved to be the male genitals which locked into place against the Velcro-like female genitalia.

"They couldn't have done it in a 'missionary position'," said Professor Long. "The very first act of copulation was done sideways, square-dance style." If that sounds unromantic, consider that at least the male and female fish would interlock their arm-like fins to avoid floating apart.

Although it eventually became a pretty big deal, sex was initially an evolutionary flop, and fish soon returned to spawning. It would be another few million years before copulation made a resurgence.