Here’s the Least-Evolved Organism on the Planet
For the sake of brevity and sanity, I’m going to assume anyone reading this has a basic understanding of evolution. If you’re accessing this site from within a locked bathroom using your parents’ evangelical cult’s community laptop, I’m sorry. I can’t be the one to introduce you to modern science. For the rest of us, we know that most organisms on earth reached their modern forms through a long process of adaptation, growing things like thumbs, gills or sacs full of poison.
You may wonder, though, is there anything that pretty much nailed it on the first try? A perfect specimen that had everything it would ever need from the moment of conception? What creature or being on Earth has had to change the least over the millennia?
Well, I have the answer for you, but it’s probably not as exciting as you were hoping for (I’ll also note that I’m not including microorganisms because the answer being “bacteria,” well, that’s no fun at all).
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For my money, I would have bet on the horseshoe crab, because it feels like those weird little freak shows will probably be the first things to contact extraterrestrials somehow. That, or you’d hope for some apex predator that’s never known defeat, who was equipped with spines and blades from the start.
The answer is neither of those things. I guess it’s not surprising in its own way that the seeming champion isn’t much more than a wet mass of cells: the sponge.
Not only have they been well-equipped to handle pretty much the entirety of life on Earth, sponges are also the oldest animal on earth, the first to emerge from life's single common ancestor: a phylum. Since roughly 640 million years ago, sponges have been perfectly content to float around and filter-feed on bacteria, and that lifestyle has never needed a drastic change. Of course they've branched off, and there’s many more species than there used to be, but that number still tops out at about 5,000.
All of which is to say, SpongeBob SquarePants may be able to track his heritage back to the planet’s first multi-cellular organisms.