According to the creation myths of the Book of Genesis, humankind is descended from two bottleneck or founder events. The first was when man was created as Adam and Eve (and even Eve was created from a tissue sample from Adam). They had thousands of descendants, including Noah, his wife, their three sons and their sons’ wives. All of humanity after the flood depicted in Genesis at Noah’s time are thus said to be descended from five people at most (Noah, his wife and his sons’ wives, assuming none of the sons’ wives were closely related to Noah or his wife). But remember that they were ultimately descended from ONE PERSON, Adam, who lived only a dozen or so generations before them, so even their genetic diversity would have to have been lower than people living today.

The reduction of a population causes a loss of genetic diversity and makes inbreeding more likely, which itself limits genetic diversity among offspring until mutation and natural selection has had time to increase that diversity.

http://en.wikipedia.org/wiki/Population_bottleneck

http://en.wikipedia.org/wiki/Founder_effect

http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml

Considering the diversity of humankind today, one would expect that humans evolved very rapidly after the flood, which would make rejection of evolution by believers in the Bible pointless. How is it that fundamentalists can beleive in rapid evolution within “kinds” over thousands of years, yet deny unlimited and slower evolution over many millions of years?

Because they reject science, of course. Dogma is everything to them, and that’s inexcusible in a society that depends on science for almost everything we have.

The dishonesty and ignorance of the Creationists becomes obvious here:

http://www.answersingenesis.org/tj/v17/i1/events.asp

By comparing DNA from different humans around the world, it has been found that all humans share roughly 99.9% of their genetic material—they are almost completely identical, genetically.⁷ This means that there is very little polymorphism, or variation. Much evidence of this genetic continuity has been found. 8 examined a 729-base pair intron (the DNA in the genome that is not read to make proteins) from a worldwide sample of 38 human males and reported no sequence variation.

These results are quite consistent with a recent human origin and a global flood. Evolutionary models of origins did not predict such low human genetic diversity. Mutations should have produced much more diversity than 0.1% over millions of years. And yet this is exactly what we would expect to find if all humans were closely related and experienced a relatively recent event in which only a few survived.

Bull$#it. If humans were NOT genetically almost identical, they would not be able to interbreed at all and would have already diversified into various species, like humans and chimps did several million years ago. The fossil record shows that species more closely related to us than chimps became extinct long ago and that our species is only a few hundred thousand years old, having evolved from older ones.

We should also seek to understand genetic evidence in the context of the tower of Babel event. 12 This too seems consistent with Biblical events in Genesis 11. Surely, much research is needed to expand ideas about such genetic evidence to determine its consistency with the Bible and its inconsistency with, for example, the various evolutionary out-of-Africa models. 13

When scientists debate issues, they start with the evidence they have and make their different hypotheses fit the evidence, then look for more evidence to rule out competing ideas. They don’t start with a creation myth that can never be ruled out and assume that any evidence must be forced to fit it!