No, allel mutation is not cupious. A lot of mixing occurs due to fertilisation, but mutation of allels does not occur often.
Over the lifetime of a population, it does occur often. According to
Molecular Evolution: A Phylogenetic Approach (Page, Colmes; Blackwell Science, 1998), a graduate level genetics text, the average number of synonymous substitutions in mammalian nuclear DNA is about 3.5e-9 per base, per year.
There's a lot of bases, and a lot of mammals. 3 or 4 per billion bases every year is a lot of mutations to a population.
And you can't talk about over the lifetime of a population. thats doesn't make sense.
In fact, viewing it from the perspective of populations is the only way that evolution makes sense. Populations grow and divide; it makes perfect sense to talk about the "lifetime" of a population.
This message has been edited by crashfrog, 09-29-2004 02:06 PM