Some minor quibbles were addressed above. Also, let¡Çs not forget genetic drift. Sometimes innocuous, or even ¡Èuseful¡É mutations get lost in the statistical cuisinart that is reproduction. Just because you can fill in all those Punnett sqares doesn¡Çt mean nature will, nor will it respect with great fidelity the comforting probabilities of unnuanced Darwinian crosses.