Transhumanism vs. Natural Selection: Playing God in the post-Darwinian era?

The important distinction here is 'evolution' of the species as a function of its population genetics vs. the fitness functions of individual humans. The latter has very little to do with the former which requires lasting changes in the genetic macrostructure of the population. The problem here is that the 'us' constitute genotypes and genotypes are dismantled every generation - they have zero heritability. It is only their constituent parts, the genes, that have heritability. So it comes down to what zyncod implied, allelic replacement is a low probabiltiy event with such a large 'effective' population size (tremendous gene flow over vast geographic areas). It is very difficult for strong, directional selection to act without population subdivision because its local effects will always be diluted by immigration. This will tend to greatly slow (natural) human evolution in the sense of species-wide biological or morphological changes. So we should not expect any observable character displacement in the human species any time soon. The problem here is there are very few genotypes carrying unique alleles that will be lost to the population even if they fail to hear the car coming. You and I might be unique individuals, but there is really nothing unique about our individual genes. People dying in traffic represent lost genotypes - but not lost genes. The only effect is on their individual fitness - not population genetics. Again, not likely much effect on population structure here either, even if the event results in progeny. There is comparatively little variation in reproductive success among humans, even in the developing world, so just because someone 'gets lucky' a lot, has little to do with their realized fitness function, let alone any lasting impact on population structure. In our society, reproductive success is likely more influenced by parental investment than by number of mating events. And besides, birth control has largely de-coupled sex from actual human reproductive consequences. The fact that disadvantageous genotypes are medically enabled to survive and reproduce DOES increase the genetic load of the population, and will ultimately tend to make us more dependent on medical interventions to preserve the health of future generations. For example, I feel safe in predicting that the rate of premature births will increase significantly in developed countries over the next century as the current generation of 'pre-mees' begins to reproduce.This message has been edited by EZscience, 06-17-2005 02:58 PM