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There is a funny quote moving around the internet that goes something along the lines of: ‘humans are deuterostomes, which means that when they develop in the womb, the anus forms before any opening. Which means you were nothing but an asshole. While the quote is hilarious-it really got me thinking.


First and foremost, I needed to know, is this true? And as it turns out, it most definitely is true. Deuterostome translates to ‘second mouth.’ This term is used to define all the animals that have bilateral symmetry and the blastopore (the first opening in the cleavage) which develops into an anus during embyronic development.

Put simply, when we are conceived, our anus is in the center of the zygote. As we develop, our anus, which is actually our mouth until the rest of our development takes place is the first cavity. According to Byjus, “The anus develops from the first cavity formed by blastopore and followed by the formation of mouth on the opposite side. The blastopore is the small indentation in the blastula, which migrates to the opposite end, forming the endodermal layer.”

Other dueterostomes include sea stars, crinoids, and vertebrates (humans.) There are different ‘clades’ of deuterostomes: Chordata (vertebrates), Echinodermata (e.g. starfish), and Hemichordata (e.g. acorn worms).

While it’s easy to get lost in what all of this means, put simply, the difference between a deuterostome and a protostome (a non-deuterostome) is that a deuterostome has a blastopore that develops into an anus, which later turns into our mouth. I don’t know about you, but that is pretty crazy if you think about it.

And for a good laugh now and again, it’s also pretty funny to think that at one point, we were all nothing but an asshole.