It goes without saying that the various human sub-species we have now, and any other speciation of hominids that may have occurred in humanity, could not have come from a pair of modern humans. The only way you could possibly theorise it happening is that every "Kind" or "Family" of creature has a progenitor-pair that was physiologically different from all the descended creatures alive today. Essentially, the rules for us, do not apply to Adam & Eve, or the generations closer to them, despite us being descended from them. They would have had to have been designed to produce a wide variety of genetic expressions in their offspring, but once you get generations upon generations down the line, the creatures lose that ability, each branch becomes specialised towards different traits and isolation cements the disparity. Whilst there are negative consequences for us to engage in incest, the divergence between siblings back must have allowed for it, by necessity. Then there are selection pressures & socio-sexual biases, as well as breeding habits that all influence the result too. Where as Evolution asserts that one "Family" of creature can gradually mutate into another, and we are all derived from single cell organisms, and have shared ancestry with animals. Mutations are like random noise, they are the chaotic product of entropy, which can then be multiplied through incest. Some add random information, others subtract it. The assertion is that all the DNA data that makes us up is completely random, and was always random, so it's therefore plausible for one 'data-set' to gradually transform into a wildly different 'data-set' and only the ones that still function/ survive in the relevant environment live on. It's like the 'immortal monkey with a typewriter in isolation' hypothetical concept though- no, the monkey is not going to eventually write an essay, no matter how long you leave it there. In reality, it will go insane due to the eventual lack of stimuli, the isolation & the surrealness of it all, and try to bash it's own head in or something like that, so it's a dumb hypothetical. Ice crystals forming into orderly shapes out of chaotic liquid is not proof of "Ordo Ab Chao," it's just one of those background parameters of reality that are another form of order- and I don't see how that can be randomly determined by nothingness or how any parameters/ laws of reality can be determined randomly.