The origin of sex might not be as sexy as we’d like to think; picture two tiny fish called Placoderms in a chilly Scottish lake and it's hardly a steamy scene.
But what is hot news is the discovery by Flinders University Palaeontologist Professor John Long that the first fish to copulate had developed specialised sex organs - a pair of L-shaped genital limbs called "claspers" on the male, and a bony orifice on the female.
he said the two short arm-like appendages probably enabled the fish to interlock arms so they could copulate sideways.
"They couldn’t have done it in a missionary position – the very first act of copulation was done sideways, square dance style" he said.
The placoderms, aptly called Microbrachius dicki, were named for the two little arms that had baffled scientists for centuries.
It was only after stumbling upon a single fossil bone in a collection in Estonis last year that the appendages' role as a sexual assistant became clear.
"Copulation, the intimate act of sexual intimacy to reproduce, was something we always think of in human terms, mammalian terms, but sharks copulate and fossil fish called placoderms were the very first type of animals to invent this kind of behaviour."
The findings, published in the prestigious journal Nature, reveaed sex was twice as old as the first dinosaurs.
Fish were also the first known creatures to evolve separate genders in vertebrate evolution - something that has scientists excited.
"These fossils are incredibly common in museum collections right around the world, there’s hundreds of them in museums in England and Scotland and America, yet we’re the first time to actually pick up they had distinct male and female sexual organs," Professor Long said.
He said the move from spawning to internal fertilisation with young being carried inside the female was significant as it was the very start of behaviours that created humans.
"Placoderms were thought to be a dead-end group with no relevance to modern living animals – recently though, discoveries like this and others recently published show placoderms are deeply rooted in the ancestry of all of us, and many of the features we have, such as jaws, teeth and paired limbs originated with this group of fishes - so by studying them and their anatomy we’re learning more about our own deep, distant evolution," he said.
And it appeared the first sex didn’t last long, with fish losing the ability to copulate, only to re-evolve sexual intercourse as we know it later on. Another mystery science is yet to put to bed.
Share
