Natural selection allows using random noise to propel in a non-random direction.

The gradient is implied by survival.

You don't get to pick the gradient beyond that.

Things that do not survive are snuffed out of the variation pool.

Things that do survive and replicate are more likely to be found in the next time step.

This is a fundamental thing that must be true, similar to the inescapability of entropy.

Noise that is not useful evaporates.

Noise that turns out to be useful is durable and persists.