Watch: Pooping Comb Jellies Just Upended Gut Evolution
The animals were long thought to live without an anus, but new videos of them pooping show that biologists were not ready for this jelly.
There’s an origin story about butts: Once upon a time, all animals were essentially blobs with mouths, and they had to eat and defecate through that single hole. But over the millennia, some blobs straightened out and gave way to animals with heads to ingest food on one end, anuses to defecate at the other, and guts in between.
The story is based on today’s animals. Those so odd they’re sometimes mistaken for plants—like sponges, sea anemones, and gelatinous jellies—have one hole. And evidence from DNA and fossils suggest that these creatures descend directly from the first animals that evolved more than 540 million years ago.
Other animals, including rats, flies, snails, worms, and humans, share a more recent ancestor with a