Mutation Rates and the Age of the Human Race

Brian Thomas, a science writer for the ICR, has an article up titled "New Genome Projects Data Indicate a Young Human Race."  He refers to three recent studies (done for the "1000 Genomes Project") summarized in the journal Science which determined that each human born carries an average of sixty mutations, down from an earlier estimate of one hundred.  Thomas raises two separate questions regarding this finding.  On the one hand, does the new lower rate provide for enough changes to derive humans and other primates from a common ancestor over the last few dozen million years?  On the other, will not the accumulation of harmful mutations over time wipe out the human species, and does this not imply a maximum possible age for the human race?

Thomas used a program called Mendel's Accountant to model a human population over time, assuming sixty mutations per individual.  He notes the result:

Assuming a population size of 2,000 individuals, assuming that each mother has six children, and using the rate of 60 mutations per generation in the algorithms, the simulation shows the extinction of the human race after only 350 generations. This also assumes that natural selection would have been effective at removing the least fit from the population every generation.

This account does not mention the percentage of mutations which are beneficial, harmful, or neutral or near-neutral, which the program allows one to select, and whose values, one assumes, would have major import on the outcome of the experiment.  I also cannot help but note that Thomas, as a writer for the ICR, is supposed to assume that human populations started out much smaller than 2000 individuals, and have apparently ended up much larger.  But that aside, Thomas notes that evolutionists assume that the human species is far, far more than 350 generations old (it is unlikely that H. sapiens is less than 10,000 generations old, and of course we have pre-sapiens ancestors going back long, long before that), whereas creationists assume that the human species is only about 300 generations old (having gone through a really intense bottleneck around 4500 years ago, when our effective population was reduced to Ham, Shem, Japheth, and their three unnamed wives; I wonder if Thomas tried to model that particular feature).

Here is one thing that struck me: the human genome is about the same size as most other mammalian genomes, and there's no obvious reason to suppose that our mutation rate differs much.  If we can't survive for a thousand generations, much less ten thousand or ten million, then it's hard to see how rats could.  Rats rarely live more than a year in the wild, reach sexual maturity in under two months, and so can have several generations a year.  I think that what Brian Thomas' use of "the latest and most accurate research into human genetics" has proved that all rodent species (not to mention all domestic mammals and indeed most supposedly extant mammals) are extinct, which is a somewhat problematic outcome.   I cannot help but feel that further research into population genetics, or perhaps just into the assumptions programmed into Mendel's Accountant, are warranted.