The origins of sex

It has been revealed that the first species to engage in sexual intercourse existed approximately 385 millions years ago, and occurred in a lake in modern day Scotland.


The fish, Microbrachius dicki, relied on a bone based ‘genital limb’ of the assumed male which inserted into small paired bones on the assumed female in a similar way to the one we’re currently familiar. The pelvic plates were revealed in the fossils of the placoderm M. dicki, and analysed by a research team led by Dr John Long of Flinders University. The article was published in Nature earlier this month. Dr Long is quoted as stating “Placoderms were once thought to be a dead-end group with no live relatives, but recent studies show that our own evolution is deeply rooted in placoderms and that many of the features we have – such as jaws, teeth, and paired limbs – first originated in this group of fishes.”

It is believed that these findings will lead to a shake up in where placoderms are considered in evolutionary history. While M. dicki is the earliest species to have reproductive organs designed for internal fertilisation, it isn’t the only placoderm. It raises the possibility that placoderms are a more unified phylogeny. It also means that it is possible that some externally fertilising fish have evolved from these internally fertilising fish. Both these possibilities were suggested by Martin Brazeau of Imperial College London.


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Luke Spindler

Research technician at the University of York working on species identification via archaeological bone collagen. Graduate in archaeology and biochemistry (MSc and BSc, respectively), and science/archaeology enthusiast. Potentially lacking in a broad range of research and personal interests.

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