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Turns Out These Tiny Ancient Fish Were The Geniuses That Invented Sex

Too bad it didn't catch on again for millions of years.

Reproduction didn't used to be so intimate. Hundreds of millions of years ago, you didn't even touch your partner when you made babies with them if you were an ancient fish. You just dropped your eggs off in the water and hoped a male fish would come along to fertilize them. But now, scientists have found the fish that invented actual sex.

The first animals to touch each other while doin' it were tiny freshwater fish that lived in present day Scotland 385 million years ago. The species is known in the science world as Microbrachius dicki -- and it was named even before scientists figured out what it was famous for.

Professor John Long, who works at Flinders University in Australia, was the lead author on the paper that revealed how M. dicki was the first known species to fertilize their eggs internally. He figured out how they must have mated by looking over old fossils and noticing that the male fish's sexual organs were perfectly shaped to "latch on" to the female's genital plates.

Due to their anatomy, the fish couldn't face each other while mating, but had to link arms and copulate side by side. It's kind of a cute move when you think about it, but it didn't catch on among the larger fish populace. Spawning became the only method of reproduction again after these fish died out, and direct copulation didn't reemerge until millions of years later.

These little guys were just way ahead of their time.