Postdiluvian genetic variation

This article from Robert Carter raises some interesting ideas concerning genetic variation.

People have 2 sets (diploid) of chromosomes. Many of our genes are identical, but several have variants. Consider the maximum variation at creation. Adam had 2 sets of autosomes, 1 X chromosome, and 1 Y chromosome. Eve was made from his side. God could have kept the autosomes, doubled the X chromosome, and removed the Y chromosome. But God could also have created Eve with her own set of chromosomes. Several genes may have been identical, but if we consider the maximum, then the original variation in Adam and Eve was (a maximum of) 4 alleles for each gene in all the autosomes, 2 from Adam and 2 from Eve; 3 alleles in the X chromosomes, 1 from Adam and 2 from Eve; 1 allele in the Y chromosome, from Adam; and 1 mitochondrial allele per gene from Eve. This assumes that all Eve's mitochondria had identical DNA. Sperm have mitochondria but these are not incorporated into the embryo so only the female's mitochondrial DNA is passed on.

Mutation and recombination would have increased the number of alleles in Adam's descendants to the time of the Flood. Carter discusses the genetic bottleneck at the time of the deluge and mentions the maximum number of variants this would entail.

On the Ark we have Noah, his wife, their 3 sons, and their sons' wives. The genetic material of the sons is determined by their parents, and the genetic material of the wives is potentially independent; depending on their relationship to Noah's bloodline. Thus we have 4 sets of autosomes from Noah and his wife, 3 X chromosomes, and 1 Y chromosome, 2 mitochondrial lineages. The sons could potentially inherit all 4 autosomes, both Xs from their mother (but not their father's X), 1 Y from their father, 1 mitochondrial from their mother. The sons' wives could have 6 autosomes, 6 Xs, no Ys, and 3 mitochondrial. Considering the offspring of Shem, Ham and Japheth and their wives there is a maximum of:

• 10 autosomes;
• 8 X chromosomes;
• 1 Y chromosomes; and
• 3 mitochondrial chromosomes.

The mitochondria of Noah's sons (from their mother) will not be passed on. The mitochondrial variation may be somewhat more as several mitochondria are passed on and they may not all be identical within a single person.

The descendants of Shem, Ham and Japheth encompasses the entire human race. Carter considers the variation we currently find.

[We] are potentially looking at a huge amount of genetic diversity within the X chromosomes of the world.

Does this fit the evidence? Absolutely! It turns out that Y chromosomes are similar worldwide. According to the evolutionists, no “ancient” (i.e., highly mutated or highly divergent) Y chromosomes have been found. This serves as a bit of a puzzle to the evolutionist, and they have had to resort to calling for a higher “reproductive variance” among men than women, high rates of “gene conversion” in the Y chromosome, or perhaps a “selective sweep” that wiped out the other male lines. For the biblical model, it is a beautiful correlation and we can take it as is.

The evidence from mitochondrial DNA fits our model just as neatly as the Y chromosome data. As it turns out, there are three main mitochondrial DNA lineages found across the world. The evolutionists have labeled these lines “M”, “N”, and “R”, so we’ll refer to them by the same names. They would not say these came off the Ark. They claim they were derived from older lines found in Africa, but this is based on a suite of assumptions (I discussed these in detail in a recent article in the Journal of Creation). It also turns out that M, N, and R differ by only a few mutations. This gives us some indication of the amount of mutation that occurred in the generations prior to the Flood.

Let’s assume ten female generations from Eve to the ladies on the Ark. M and N are separated by about 8 mutations (a small fraction of the 16,500 letters in the mitochondrial genome). R is only 1 mutation away from N. This is an indication of the mutational load that occurred before the Flood. Given the assumption that mutations occur at equal rates in all lines, about four mutations separate M and N each from Eve (maybe four mutations in each line in ten generations). But what about R? It is very similar to N. Were N and R sisters, or perhaps more closely related to each other than they were to M? We’ll never know, but it sure is fascinating to think about.

One more line of evidence crops up in the amount of genetic diversity that has been found within people worldwide. Essentially, much less has been found than most (i.e., evolutionists!) predicted. The general lack of diversity among people is the reason the Out of Africa model has humanity going through a disastrous, near-extinction bottleneck with only about 10,000 (and perhaps as few as 1,000) people surviving. However, the reason for this lack of diversity is twofold. First, the human race started out with only two people. Second, the human race is not that old and has not accumulated a lot of mutations, despite the high mutation rate. Third, there actually was a bottleneck event, Noah’s Flood!