As discussed above, neo-Darwinism must be clearly defined in order to
determine if these are a part of it. Although natural selection is
generally agreed to be very important in the course of biological
evolution, no biologist or paleontologist should think it accounts for
everything in light of the available evidence. Genetic processes such as
genetic drift are particularly important when pressure from natural
selection is weak. Catastrophes are another factor outside of natural
selection that may have had a large impact on the course of evolution. A
classic example of this problem is a set of twins, one of whom gets hit by
lightning but the other lives and has lots of kids. Obviously, natural
selection acting on the genes was not relevant. Likewise, there is hardly
any genetic factor which will better enable an organism to survive a bolide
impact in the immediate vicinity. "Survival of the fit enough" rather than
the fittest is a more accurate picture of evolution.
David C.