A new study suggests that humans’ anuses may have originated from a sperm chute in tiny, worm-like creatures called xenacoelomorphs. Researchers at the University of Bergen in Norway investigated the genetics of these distant relatives of flatworms and found that they use some of the same genes to create a genital opening as they do for waste disposal.
According to zoologist Andreas Hejnol, “Once a hole is there, you can use it for other things.” The study’s findings reveal that xenacoelomorphs have a unique reproductive system where males release sperm through a separate opening, while females use their mouths to expel eggs, food, and waste.
The discovery has sparked debate about the evolution of the anus in animals. While some researchers believe that humans’ anuses evolved after our branch of the animal family tree diverged from xenacoelomorphs’ ancestors, others argue that these flatworm-like animals developed a butt hole and later lost it, potentially placing them in a different position on the evolutionary tree.
The study’s findings have implications for our understanding of human evolution. If we did not develop an anus that is separate from our mouths – a throughgut – like modern animals do, we may be smaller than our worm-like ancestors. The research has been uploaded to biorxiv and is awaiting peer review.
Source: https://www.sciencealert.com/wild-new-study-suggests-buttholes-once-had-a-very-different-purpose