Scientists studying fossils discovered that the placoderm fish Microbrachius dicki, which lived about 385 million years ago in Scotland, were the earliest vertebrates to engage in sexual intercourse. Male M. dicki developed bony genital claspers to transfer sperm to females, while females evolved small paired bones to lock the males in place during mating. This finding shows that placoderms were the first to evolve many features that later characterized humans, including sexual reproduction.