"Very close cousins like humans and chimps have almost all their genes in common. Slightly less close cousins like humans and monkeys still have recognizably the same genes. You could carry on right on down to humans and bacteria, and you will find continuous compelling evidence for the hierarchical tree of cousinship."

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Intelligence is a valuable thing, but it is not usually the key to survival. Sheer fecundity ... usually counts. The intelligent gorilla doesn't do as well as the less intelligent but more-fecund rat, which doesn't do as well as the still-less-intelligent but still-more-fecund cockroach, which doesn't do as well as the minimally-intelligent but maximally-fecund bacterium.

— Isaac Asimov