Scientists Discover What They Believe To Be The Origins Of Sex
The origins of sex may have been discovered in reproductive patterns of ancient fish, the first animal to become impregnated by way of intercourse.
Known as Microbrachius dicki or M. dicki, the fish was about 3 inches long and lived 385 million years ago in the surrounding waters of what is known now as Scotland.
An L-shaped appendage on M. dicki stood out to Long, who soon realized it was the male fish’s sex organ.
When he analyzed the female fish’s anatomy, he discovered a plate where the male’s genitalia could be inserted.
They most likely mated side-by-side, the fish’s curved fins allowing them to stay intact.
Long told the BBC,
The little arms are very useful to link the male and female together, so the male can get this large L-shaped sexual organ into position to dock with the female’s genital plates, which are very rough like cheese graters.
They act like Velcro, locking the male organ into position to transfer sperm.
This male fish has the oldest sex organ currently known.
We have defined the very point in evolution where the origin of internal fertilization in all animals began. That is a really big step.
The sex only lasted for a bit, however, as primitive aquatic creatures quickly went back to laying eggs and releasing sperm into the water.
Millions of years passed before intercourse returned in the animals that evolved into sharks and stingrays.
The reason for these changes, Mashable reports, remains unknown.
It could be a change in environment or a special adaptation that happened at the time.
The discovery also makes M. dicki the first species in which the two sexes possessed different genitalia and thus different appearances.