Well, there’s another few steps, of course.
Because at some point, operating along lines of logic that worked out perfectly so far, you did decide to be a mammal.
A mammal is a machine for adapting to Circumstances. A mammal is a tremendously resilient all-terrain life-support system, with built-in heating, cooling, respiration, and incubators for reproduction. Mammals internalise everything (grudges, eggs) and furthermore are excessively, flamboyantly wet internally. Sure, everyone’s a bag of chemicals; but mammals slosh. Mammals took the concept of an internal ocean and took it in an unnecessarily splashy direction, added aftermarket mods and a climate-control system,
and just to show off, you leaned across the metaphorical gambling table and said: “my internal ocean is so good-“
“Bullshit,” said the shark, keeping it salty (ha)
“My internal ocean is so brilliantly resilient, more so than any of YOURS,” you said, holding their attention with a digit held aloft, “that for my next trick, I shall artistically recreate the ballad of evolution as a performance. I shall craft a complex chemical ballet depicting the origin of multicellular life - using some of my own material, of course-”
“Oh, ANYONE can lay an egg,” yodel the fish, and the ray adds: “ontogeny does NOT recapitulate phylogeny!!”
And you’re like, “yeah no, it’s an artistic rendition, not a literal thing. Basically I’m going to take some cells and brew them up-“
“Like an egg. An egg but internally.”
“Yeah,” said the viviparous reptile, “yeah, like, that can work really well. I’ve always said it’s the highest test of one’s chemical know-how. It’s a lot of work. And forget about support from your family - forget about support from your PHYLUM - all you get is criticism.”
“I’m gonna do it on purpose forever,” you said. “The highest chemical, thermoregulatory, immunological, everything-logical challenge. It’s gonna be my thing.”
“I’m with you,” said a viviparous fish, stoutly. “Representation.”
You kindly don’t point out, once again, that you’re planning to do this outside the ocean, in a range of temperatures; carrying the dividing cells in a perfect 37.5• solution of saline broth in all terrains, breathing oxygen in a complicated matter, you know, bit more difficult; but you need your allies.
“It’s solid,” says the coelacanth.
“But is it metal?” says the deep-vent organism.
“Oh, it’s metal. I will feed the young,” you say, magnificently, “on an echo of the mother ocean. The first rich feast of cellular matter, the first hunt for sustenance, the first bite they sip of our liquid planet-”
“Will be a blood byproduct. My own blood byproduct.”
Everyone looks uncomfortable.
“But,” a hagfish says carefully, “don’t you outdoorsy guys still need your blood?”
You cough and explain that if you stay wet enough internally and hydrate frequently, you should be able to produce enough blood byproduct to sustain your hellish new invention until they can eat your peers.
The outrage that follows includes questions like “is this some furry shit?” And: “milk has WATER in it?”
And you won the bet. “My inner ocean is such a perfect homage to the primordial soup that I can personally cook up an entire live hairy mammal in it. And then generate excess blood byproduct from my body and give it to the small mammal until it gets big.”
That is an absolutely bonkers pitch, by the way, and everyone thought you were a showoff, even before the opposable thumbs. When the winter came, and the winter of winters, and the rain was acid and the air was poison on the tender shells of their eggs and choked the children in the shells; when the plants turned to poison, and the ocean turned against you all; when the climate changed, and the world’s children fell to shadow; your internal ocean was it that held true. A bet laid against the changing fates, a bet laid by a small beast against climate and geography and the forces of outer space, that you won. The dinosaurs fell and the pterosaurs fell and the marine reptiles dwindled, and you, furthest-child, least-looked-for, long-range-spaceship, held hope internally at 37.5 degrees. Which is another thing that humans do, sometimes.