A recent Panda's Thumb post highlighted that, given the size of the human genome, the rate of
de novo point mutations, and the total size of the population, every non-lethal position can be expected to vary - meaning that, for every genome position or
site, there's very likely at least one person (and usually dozens or more) with a new mutation there, so long as it's non-lethal. It's a trivial calculation and, while we could refine it in various ways, the essential point is clear.
 |
"We are all, regardless of race,
genetically 99.9% the same."
Right or wrong? |
Still, let's try to understand this a bit further. First, an equally simple, entirely compatible fact which might attenuate our surprise: the existence of a couple hundred people with new mutations in a certain site leaves about seven billion
without a new mutation there. Indeed, at the vast majority of sites, almost all people are homozygous for the same allele - identical by descent from the hominid lineage.
In that light, here's a deep question one can ask about all those hundreds of billions of
de novo mutations: what will be their ultimate fate? Will they all shuffle through the future human population, making our genome's future evolution look like the reels on a slot machine? Or is it going to be rather more like
the pitch drop experiment?
