Issue comprehending Genesis and the Great Flood Ok so just from an empirically measurable perspective, we know that inbreeding leads to deformed offspring, why didn't this happen with Adam and Eve, and Noah and whoever he choose to go on board the ship with him?

To clarify, how could their siblings then go one to produce offspring without having sex witn their brothers , sisters , father or mother? 

I'm also confused as to how humans split into differing distinct racial profiles, how does and where does the Bible explain this part?

Many thanks in advance

reference literature on inbreeding
Young earth creationists do indeed believe that Adam and Eve's children would have paired up to reproduce. They do not believe that this would have caused deformed offspring because  at that time their DNA was in a relatively good state. YECs believe that genetic decay is a consequence of the fall. Even if each of Adam and Eve's children had a hundred new mutations, they would have each had different ones. Many of the genetic deformities we know today require both parents to have the mutation, so the first generation would have been mostly safe. As long as that generation's children didn't breed exclusively with their own siblings, their mutations would also not match their partners'.

YECs generally assume that Adam and Eve remained fertile for quite some time, with sons like Seth being born after 100 years, and presumably more even later than that. This means that the children of Adam and Eve who married each other may not have been raised together; many could have even been virtual strangers before pairing up. The Westermarck effect thus could have remained in place, and technical incest could have occurred without the social problems that we associate with it now.

As to the nations and 'racial' appearances after the flood, well YECs believe that the Tower of Babel story provides the answer. After the languages were confused the peoples of the world would have spread out, with smaller ones fleeing faster and further in order to escape the chaos and conflict. The larger groups probably remained closer, and would have had more people knowledgable with each technological advance, so that the "cradles" of civilisation we see are centred around Mesopotamia, while nations further away seemed more primitive. As groups spread out, their gene pools shrink, and certain characteristics get emphasised in each. One of the most obvious traits, skin colour, would be caused by the sun: near the equator those with light skin would have died more from skin cancer, while those near the poles with dark skin would have suffered from rickets and other vitamin D deficiencies. Natural selection would thus select the most advantageous skin colour for the climate.