The answer is simple: natural selection. Deleterious mutations quickly work their way out of the gene pool.
Exceptions to this are obvious -- artificial environments, like inbreeding, where good genes don't have a chance to compete with bad genes and situations where normally deleterious mutations actually provide a selective advantage (Tay Sachs and Sickle Cell being prominent examples).
Mutations that confer a selective advantage may be relatively rare, but because of the low survival and reproduction rate of most animals in the world, even a small selective advantage can be tremendously significant and that trait will generally spread quickly by the process of gene flow.
Yes, I knew you did not finish the article.
“Mutations that confer a selective advantage may be relatively rare, but because of the low survival and reproduction rate of most animals in the world, even a small selective advantage can be tremendously significant and that trait will generally spread quickly by the process of gene flow.”
You missed the point. This is not attempt to disprove evolution. The point is, so far, there is no actual evidence of it, and it’s not the only possible explanation. Take your statement. You know this, how? It’s just a supposition, a plausible one maybe, but not demonstrated.
No one doubts there are “evolutionary changes” within a species, as the author points out, but there is absolutely no evidence of mutation ever resulting in a new species.
Hank
I did. Toward the bottom, she throws out ID and evolution and claims that species are fixed but shaped (somehow) by the environment. She is a woman with big opinions and very few facts.
At the bottom it says that she was involved with genetics. I found another article by her promoting euthanizing the elderly, where it says that she was involved in medicine, but she has been a full-time writer since 1996 at least. She was probably a nurse.