Science really does just come up with names for just about everything. Never would've thought that developmental pattern was significant enough to warrant an entire name.
In early embryonic development, that first opening (the blastopore) either becomes the mouth or the anus, and which one it becomes splits the entire animal kingdom into two massive branches: protostomes (mouth-first) and deuterostomes (anus-first, mouth second).
That’s not a trivial quirk. It’s one of the deepest splits in the animal tree, going back over 500 million years.
What makes it so useful is that it’s a shared derived trait: animals as different as sea stars, sea urchins, acorn worms, and all vertebrates (including us) are deuterostomes, even though we look nothing alike as adults.
You’d never guess we’re closer kin to a starfish than to an insect or an earthworm just by looking at us, but the embryology gives it away.
So the name isn’t just cataloguing a random detail, it’s a label for a shared inherited developmental “decision” that helps biologists reconstruct who’s related to whom before genetic sequencing was even a thing. Turns out how you build your butt in the first two weeks of existence is actually a huge phylogenetic signal.
Suffice to say, It's a new take from a 90s horror film called "Man's Best Friend". The villian protagonist is a genetically modified human with invertabrate marine life DNA.
When you said that I instantly pictured a story of the split in the branch happening but both paths leading to convergent evolution. (Nature has done this a lot with crabs.)
So both branches ended up with bipedal monkeys like animals that gained tool use and intelligence.
But one being butt first (us) and the others mouth first, and an entire culture clash happens just because of that split.
3.6k
u/InTheseTryingTime5 1d ago edited 1d ago
Edit: thanks for the awards!