RufusAtticus

wehappyfew,

First thing, H-W equ. is probably not applicable to your question because some of the initial assumptions are invalid, such as gene mutation.

From my encounters, creationists use that argument to counter claims that a YEC scenario does not allow enough time for the observed genetic diversity to evolve from two individuals. They posit that the current genetic diversity evolved via intragenic recombination. They however have shot themselves in the foot because that situation actually takes more time than one generated by point mutations. Recombination rates also differ greatly so we should see more nucleotide diversity in the "hotspots." This is not observed.

For a genome the size of the human genome one point mutation occurs every three cellular divisions. Thus on average, an ova will have 4 point mutations (24 cellular divisions in the life time of an egg and ½ genetic material), and a sperm will have any where from 25 to over 100 point mutations (the older the male the more divisions occur). So any individual will differ from its parents on average by 30 to 100 point mutations.

Nucleotide mutations resulting from recombination is much lower. (I’m still trying to dig up an exact number.) The average number of recombination events per chromosome pair per meiosis is between 1 and 2. (IIRC) That’s 23-46 per meiosis. Consider the probability that a recombination actually generates a novel allele. I would argue that even if Adam and Eve had a large amount of nucleotide diversity, recombination would generate far fewer new alleles than point mutations.

Also in this scenario, there would be no diversity in the Y chromosome because Adam and Eve would only contain one copy. However, there is enough diversity in Y chromosomes for some ethnic groups (like the Welsh) to have “distinctive” Y chromosomes.

The situation also doesn’t explain how for some genes alleles are more similar between species than within a species. I think this is a common situation for blood factors. Here’s a page that gives some examples: Blood Group Antigen Database. If all human alleles are related by descent from Adam and Eve than they should be more similar to one another than to any alleles found in other species. This is not true.

~~RvFvS~~

Dr.GH

One of the really powerful contributions of the Hardy-Weinberg equilibria eq. is that you can use it to estimate the frequency distribution of recessive genes. "Ab" is phenotypically "A" and in most terms the expresion of "A" is what is acted on by selection, but not always (recessives like that associated with sickle-cell anemia may be positively selected for under certain environmental condiitons).

Quetzal

And to add weight to what Rufus said about limited allelic variance among human populations, see the article I just posted in scigirl/Douglas debate part 2 concerning single nucleotide polymorphism.

Human populations show remarkably little genetic diversity - proving that our ancestors left Africa less than 3000 generations ago. There is actually more genetic diversity between individual chimps than there is between individual humans - meaning the speciation event that separated Homo from its parent species took place substantially less time ago than the speciation event that separated the ancestor of Pan from the ancestor of human.

wdog

ok, thanks rufus

ps418

Rufus - thanks for bringing up these excellent points. I look forward to reading more posts from you in the future.

Patrick

RufusAtticus

bump

tk

The population in the model doesn't evolve because the various generations are assumed to have a 100% survival rate. In order for natural selection to occur, so that the genes in successive generations will tend towards say aa, it's necessary to introduce an extra factor into the model which decreases the survival rates of AA and Aa people.

RufusAtticus

Actually, you can relax any of the initial assumptions to get the population to evolve.

1. Add Selection (viability and/or fertility).
2. Add Drift
3. Add Migration
4. Add non-random mating.
5. etc.