SPECIAL REPORT: HOW SEX WAS INVENTED

- Once upon a time there was a daddy placoderm and a mummy placoderm, and they liked each other a lot. So, one day, these two placoderms stood next to one another and had sex, and it was the first time sex as we (tangentially) know it had happened on planet Earth. 

Few similarities to human sex
This is what scientists announced this week following a detailed analysis of fossils discovered in as geographically unaffiliated destinations as Scotland, China and Estonia. The animals in questions lived not in the sea, but in lakes, and existed around 380 million years ago. Mankind earliest ancestor was believed to have lived only 1.8 million years ago.
The logistics of the coupling bore very few similarities to human sex. Firstly, the animals did not face each other or go approach "doggy style" from the read. Instead, the animals floated side by side "as if they were square dancing."As for genitals, they were to be found at the bottom end of the organism, where the feet would be on a human. The male had a pair of claspers, long, rigid, L-shaped appendages. The female had genital plates which formed a small area on her backside.
These genital plates were described in the paper as being like a cheese grater. This rough texture would cause the male claspers to get locked in place and allow the transfer of sperm to commence.
Strangely, over time fish seem to have lost the ability to have sex this way, with eggs being fertilised inside the body of the female. Modern fish release eggs and sperm into the water where they are then fertilised, outside of the body. Why this happened remains a mystery to scientists.