This particular odd ape suggests that you go find a beginning biology text and read up on such things as earthworm hearts. Ten little pulsing enlargements in blood vessels... a great sort of start to build on over a few hundred million years.
It doesn't belong on this thread, but how about the hemoglobin C mutation which is fairly common in West Africa? It gives homozygotes a 93% lower incidence of malaria, with only occasional ill effects in some of the people with it. If you are remotely interested, Sonnikke, I'll start a thread on it.