Researchers from Australia believe they have identified the first animals to procreate by having internal sex.

Researchers from Australia believe they have identified the first animals to procreate by having internal sex.

This discovery is based on evidence from fossils found in Scotland of prehistoric fish which lived around 385 million years ago.

According to the study, the ancient armored fish were among the first animals to evolve sexual organs for intercourse.

Because of the L-shape of the male sexual organ, the fish had to have sex while swimming side by side.

The bone structure of the fish reveals that the male and female would interlock arms while mating.

Before fish evolved to be able to have sex, they would spawn, which is when females lay their eggs in the water, and the eggs are fertilized with male sperm externally after they have already been laid.

Lead author of the study, Professor John Long, from Flinders University in Australia is quoted as saying: “This is not just about bony structures on these fish, it's about the evolution of behaviour, of when sex first became fun.”

Experts think that fish went back to spawning before sexual procreation started happening again in shark and sting ray ancestors.