Q:

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 

A:

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.

A:

"we know that inbreeding leads to deformed offspring"
No, we don't know that.  (Or if we do, we have been misinformed.)
Consider Queen Cleopatra of Egypt, whose ancestry is well documented.
For five generations back, all of her ancestors descended from the same couple.
Most people have 64 great-great-great-great-grandparents.  Cleopatra had only 2.
If that's not an incestuous family tree, I don't know what is.  Yet no one says "So that's why Cleopatra was so deformed!".
Yes, if someone has a broken gene and their descendants interbreed, there is a greater chance that a child will end up with two copies of that gene.  But the risk usually isn't high.  When it does happen it typically means that that child won't have children of its own, thereby reducing the incidence of the bad gene from the gene pool.  Except for the obvious case of the child itself, this is a good thing.
Here's an extract from something I wrote elsewhere about cousin marriages:

Inheritance
People's DNA has two copies of each gene. If one copy
happens to be non-functional, that's usually okay as the other will
provide whatever genetic information is necessary.
The problem is that if a common grandparent has a defective gene, two
grandchildren could each inherit that gene and both could pass it on
to their child. If that child has a gene where both copies are
defective, the child will have the disease, disability, deformity,
etc. associated with it. If the grandparent does have a defective
gene, the chance that a great-grandchild will inherit two copies of it
through their first-cousin parents is one in sixteen (6.25%).
Consider a common inherited disease such as Cystic Fibrosis. Among
northern Europeans, one person in twenty-five carries the damaged
gene. This means that the chance that a child of first-cousin parents
inherits both damaged genes from its double great-grandfather is
1/16th of 1/25th, or one in 400 (.25%).
Most inherited diseases are far far rarer than one in twenty-five, so
that .25% rate for C.F. represents an extreme case.
Risk
Now suppose we consider a rate of .25% to be too high a risk, and
use it to justify declaring such marriages illegal. What are the
implications of this?
If we applied the same criterion to Down's Syndrome, we would have to
make it illegal for women over 32 years old to conceive children, as
the percentage of 16-week fetuses with Down's Syndrome is higher than
.25% for 33 year old mothers. And perhaps we would have to make it a
criminal offence for any woman over 42 years old to conceive, as the
chances then are ten times higher than that.
Legally restricting conception based on the age of the mother is far
more justifiable than restricting it based on a first-cousin
relationship. But no jurisdiction has ever done that.

