Synopsis.
Name
Fit to Fail. There is a move that pays. Forage a little harder, grow a little larger, take a little more of the shared resource, press a little further than the one beside you, and you do better than the one beside you: you leave more offspring, you win more of the contested stock, your line grows where theirs shrinks. The advantage is real, not imagined, and it is relative: it is measured against your rivals, and against your rivals you come out ahead. So the trait pays, plainly, and it pays every time it is tested, because it is tested one individual against another and the one who presses harder wins. And here is the thing about a trait that raises relative fitness: it does not have to raise anything else, and it does not care what it lowers, because selection sees only the margin between you and your neighbour, not the level of the whole. So the very same pressing that lifts each individual above its rivals draws down the shared resource, thins the population's capacity to persist, lowers the viability of the whole, and none of that shows in the margin, because the margin is relative and everyone is pressing and everyone is still ranked against everyone else. One individual takes the trait and out-competes those without it. And those without it are out-competed, so they must take it too, or they are gone: the trait spreads not because anyone chooses it but because the alternative is to lose, and once some carry it all must carry it to keep up. It fixes in the population by a one-way ratchet, and it cannot come back out, because to drop it is to be out-competed by whoever still carries it, and someone always still carries it. So selection reinstalls it every generation, favouring the fitter each time, blind to the level of the whole, and each generation the population is a little fitter, individual against individual, and a little less viable, whole against its own threshold. And the viability sinks. And it sinks not despite selection but because of it, driven down by the same force that rewards each individual for pressing harder, until the population crosses the threshold below which it cannot persist, and crashes, and is gone. Nobody defected. Nobody cheated. There was no villain who took more than their share against a rule, because the trait was a genuine advantage and taking it was the fit thing to do and every individual that took it was rewarded for it, exactly as selection promised. It is only that the fittest move for the individual was the fatal move for the population, and selection, which cannot see the population, chose it, again and again, all the way past the brink.
Arc
The bend is this: a trait that raises an individual's relative fitness lowers the population's viability, and because it wins locally it spreads by a one-way ratchet and selection reinstalls it each generation, so the population is bred fitter and fitter past its own viability threshold, and crashes, extinguished by selection itself with no defector to blame. It runs on a genuine advantage. The trait is not a mistake and not a cheat: it really does raise the individual's relative fitness, so the individual that carries it out-competes the one that does not, and selection favours it because favouring the fitter is exactly what selection does (Matsuda and Abrams, on the evolution of foraging effort, a trait selected for its relative advantage carrying the population toward its own collapse). The advantage is real, which is what makes it a trap and not a fault, because there is nothing to correct in an individual doing the fit thing. And the advantage is relative, so it need lower the whole. Selection sees the margin between an individual and its rivals, not the level of the population, so a trait can win every contest it enters while drawing down the shared resource and thinning the population's capacity to persist, the gain banked individually and the cost paid collectively (Rankin and Lopez-Sepulcre, on evolutionary suicide, adaptation at the individual level driving the population to extinction). What is fit for the one is measured against the other ones, never against the survival of all of them. And because it wins locally it must spread. The individual without the trait is out-competed by the individual with it, so to keep up it must take the trait too, and once some carry it all must, and once all carry it none can drop it, because to drop it is to be out-competed by whoever still carries it (Gyllenberg and Parvinen, on the conditions under which a selected trait drives its own population extinct, the strategy fixing where no individual can afford the alternative). The ratchet turns one way: the trait fixes and cannot be selected back out. And selection reinstalls it each generation, blind to the floor. Every generation selection favours the fitter, so every generation it re-chooses the trait, and every generation the population is fitter individual against individual and less viable whole against its threshold, the viability sinking under the very force that rewards each carrier (Webb, on the classification of Darwinian extinction, the population evolving down its own viability until it crosses the point of no return). Nothing in selection can see the level of the whole, so nothing in it can stop before the floor. And the viability crosses the threshold, and the population crashes. The sinking is not noise and not bad luck: it is the direct work of the selected trait, carried past the viability floor below which the population cannot persist, and at the crossing the population collapses, driven to extinction by the same selection that rewarded every individual all the way down. No one defected: every carrier did the fit thing and was paid for it, and the ruin has no villain, only the fittest move made faithfully by all. Restrain it, from outside or from above the individual, and the viability holds: impose a limit no individual would choose, or let selection act above the individual level, on the group or the collective, so that what is favoured is the survival of the whole and not the margin of the one, and the trait is held back before it fixes and the threshold is not crossed: but this means overriding a genuine advantage, holding each individual back from a move that really would win, paying to suppress the fit thing at the level where it is fit, against selection itself which reinstalls the trait every generation, so the population persists only by paying, continuously, the cost of forbidding the winning move to every individual that would be rewarded for making it.
Stakes
Whether a population can hold its own viability, when the fittest move for each individual is the fatal move for the whole and selection can see only the margin, never the level. Every plot but the last moves the same way: toward the edge taken, which each individual is rewarded for taking and cannot afford to refuse, and away from the line held, which would forbid a move that genuinely wins and override selection at the level where the trait is fit. The production cannot make the fit move safe, because the trait's advantage is relative and real and selection reinstalls it every generation blind to the whole, so the population is bred fitter and fitter into its own collapse by the same force that rewards each carrier: no one defected and every individual did the fit thing. It can only show that the advantage was genuine and the reward was real and every carrier was paid exactly as selection promised, that the ratchet turned one way and the viability sank under the winning trait, and that the one move that holds the line, restraint imposed from outside or selection lifted above the individual to favour the survival of the whole, must be made by paying, continuously, the cost of forbidding the winning move to every individual that would be rewarded for making it, against selection itself, so the population is fit and each is rewarded and the viability it is bred past is the one thing it cannot keep.
Estate
khai-misfits: the house that holds this production and answers for the whole run.