Surely Dave even you must concede that in a reasonably diverse group of individuals one or two of them would be the better suited for a given situation than the others. Natural selection simply picks the best suited from whatever is available.
Why must you always presume a purpose has to be involved? If the previous generation managed to produce offspring in a given environment but one current individual by chance was slightly better suited than its parents, siblings and cousins, then it would be more likely to successfully produce more offspring with that same beneficial trait than they would.
Whatever the beneficial trait was would be enhanced through NS with each new brood until all the others either acquired the same trait by perhaps interbreeding or they simply perished.
Is this where statistics and ratios are used to obfuscate and argue your personal incredulity Dave?
Maybe only one beneficial mutation or genetic variation out of millions of neutral or harmful ones would be selected for, I don't know, and perhaps all it needs.
All of humanity is genetically supposed to be linked to only one unknown woman, all the others have simply fallen by the wayside, to coin a phrase.
I simply think that the smarter ones had an edge Dave and that they produced more offspring with their "smarter" genes.