It's a sieve; a filter. Genetic change comes from deeper things in the genome: that's what I was trying to point at from my criticism. Sober was talking about an idea that is antiquated; the newer models of evolution when compiled together paint a very complex picture. NS is only a small part of the whole and IS NOT the SOLE source of change. But if we're going to single out one idea that pervades every aspect of biology--no idea is more prevalent or--as I said--useful. It is the glue across all the sub-disciplines.-NS is the cause of microevolution to a degree. It does not cause speciation by itself, if it contributes at all. In the newer research all the other epigenetic mechanisms seem more important.