Fribn "engines" episode 1150
Gould ends his essay with a curious motto. "Human
equality is a contingent fact of history," he says.
"Say that five times before breakfast." Our equality
is a contingent fact of history. By contingent, he
means things might have worked out differently.

I have trouble with this. Which of the dictionar;y meanings do you think he is using?
contingent
adj.
5L contingens, prp. of contingere, to touch: see CONTACT6
1 [Obs.] touching; tangential
2 that may or may not happen; possible
3 happening by chance; accidental; fortuitous
4 unpredictable because dependent on chance
5 dependent (on or upon something uncertain); conditional
6 Logic true only under certain conditions or in certain contexts; not always or necessarily true
7 Philos. not subject to determinism; free
n.
1 an accidental or chance happening
2 a share or quota, as of troops, laborers, delegates, etc.
3 a group forming part of a larger group
con[tin4gent[ly
adv.

>5 dependent (on or upon something uncertain); conditional

going on from the same source:

As it happens, our ape ancestors branched off and survived, while our later hominid ancestors died out. If those hominids had survived, then our species, in its many colors, would coexist with truly less developed hominids. It'd be a different ball game. But that's not how it worked out. We are one -- and only one --people.

With so much time, if there had been another possibility, it would have happened. It seems
to me that history has proved that it was not contingent, that it could not have happened
otherwise.

"contingency" (e.g. in contingency plan, which was fashionable some years ago) is a term that has been mystifying me for a long time. Apparently there is a whole branch of philosophy dealing with it. Certainly it is connected with causality. An outcome is contingent upon a condition, if that condition is necessary for it, though it need not be sufficient.