[VadeRetro]

There is no selective pressure that will cause minute changes like that over eons. Are there? Am I wrong?

Where are you imagining the difficulty? There is no anchor holding you against drift. Randomness does not force a net zero change. In fact, random drift will move you in proportion to the degrees of freedom and the square root of the time factor. IOW, yes. You are wrong.

[VadeRetro]

Reading the above, some ingenious data lawyer is rushing to post, "What about things that stay unchanged for long periods?"

You stay unchanged when you're at a local fitness maximum. There are active conservative pressures to not change when you have it about right.

[longshadow]

"square root of time" placemarker