Any given useful variance is lost in the noise for the individual.

Useful == gave an edge to survive.

There's so much variance that the useful bits are swamped.

But at the level of the swarm, you average the population together and the useful variance is what stands out.

That's a consistent edge imparted by the ground truth of the universe.

That strong consistency of a subset is what makes it pops at the level of the population.

Usefulness gives a consistent edge, and that edge is determined by what actually ends up working in practice in the ground truth.