It's mutations. We track them. We count them. They're it. Deal with it.
Why? Is this an interrogative science is disallowed?
And no, science has not been able to "track" the micromutations that actually cause the complex evolution we see in nature. Micromutations occur, my wife unfortunately has a nasty one in her breast right now, but science has not demonstrated that RANDOM micromutations and natural se;ection fueled evolution. It is a theory and one which has neber yielded sufficient results.