Population and mutation
While on lunch and catching up on the aggregator, via Mankiw's blog I found that Richard Posner is worried about overpopulation. Among his six reasons is a rebuttal of sorts to the idea that with more people you get more geniuses and positives to society (as Mankiw states in a '98 ECONOMICS article), by saying that its just as likely (or more likely) that with any given extra population you get the next Hitler or Pol Pot or whatnot, and thus extra pop growth is at least a wash in this regard if not net negative.
I disagree with this, and much for the same reason I disagree with creationists who bring up mutation as some sort of refutation of evolution- that more than 9 times out of 10, a mutation is either deleterious or neutral (neutral being relative), and so mutation being far worse than anything positive, it can't be a driver of evolution.
The difference of course is that while 9 out of 10 are bad or indifferent (more like 1 out of a thousand, ten thousand, million, etc; I'll agree to a large scale of non-zero rarities, the point remains the same), over time the deleterious mutations are removed (by definition) and what you end up with is a tick-tock progression of mutation that ends up increasing fitness over time.
Thus also with population growth. Deleterious "great men" of history crop up all the time, and like biological systems and the environment, there are mechanisms to prevent their rise and, in the end, remove them from history (even if its just dying out). Positive folk's contributions, over time, accumulate and carry on. And if its deleterious mutation that you want to avoid, the answer is not "less DNA replication" but "more robust error correction/mitigation." Ditto for people.