Is there any limitation of Neo Darwinism? If yes then explain it.
Answers
Explanation:
Mutations and natural selection only effect change within a created kind; for example the mosquitoes and blind cave fish you mention (they are still mosquitoes and the same type of fish).1 Mutations only modify existing genes to create different coat colours, for example, in cattle and dogs. Dr Jean Lightner has written about this. Mutations won’t create the genes that allow an animal to produce colour where it could not before, but they can damage an existing gene so that the animal produces less brown pigment, resulting in a light colour (such as fawn or white). On the other hand, a mutation can damage the control system for pigment production causing it to run ‘full speed’ and produce much more of the pigment so the animal is black rather than brown.
These sorts of changes can give us varieties (even ‘species’) of wolves (dogs, arctic wolves, African wolves, dingoes, jackals, foxes, etc.) but they won’t change a reptile into a wolf to give rise to wolves in the first place, which requires the invention of brand new genes. We wrote about the mosquitoes you mentioned as an example of the sorts of changes that can cause rapid speciation within a created kind.
Dr Sanford is talking about the number of mutations that are slightly harmful in organisms with large genomes, like humans (and wolves). There are many slightly harmful mutations and because there are many and they are only slightly harmful, natural selection cannot get rid of them; they are effectively invisible to natural selection. Think about a mutation that resulted in a wolf being born blind. Natural selection would normally eliminate the individual with this mutation (that is, it would not survive; that’s all we mean by natural selection). Such large-effect mutations can be/are eliminated. However, we acquire something like 100 new mutations per person. Many of these are only slightly deleterious (no obvious defect). Because such mutations have only a small effect, with no obvious effect on survival, natural selection is powerless to eliminate them. Also, all offspring are born with more mutations than their parents; none have fewer. That means that these slightly harmful mutations are accumulating, generation by generation, relentlessly causing genetic deterioration because of the summed effect of all of them. It is in this context that Dr Sanford makes his conclusions about Darwinian evolution being ‘dead in the water’. The degeneration he speaks of is happening in all higher organisms. It is a pattern of deterioration that overlays everything and prevents any possibility of upward evolutionary ‘progress’ (“climbing mount improbable”) that is supposed to have changed a microbe into a microbiologist.