"Nothing can be effected, unless favourable variations occur, and variation itself is apparently always a very slow process. The process will often be greatly retarded by free intercrossing. Many will explain that these several causes are amply sufficient wholly to stop to the action of natural selection." Charles Darwin, Origin of Species 1st edition (on Kindle)
One of the criticisms of Darwin was that any favorable mutation would be diluted in the next generation by blending. So for example, if a mutation caused an organism to be 50% taller, it's offspring would be 25% taller because they mated with a normal height. The grandchildren would be 12.5% taller for the same reason and so on until the original mutation was gone. Now, given the particulate theory of inheritance we know that blending is not how it works but alleles are passed on.
"Nothing can be effected, unless favourable variations occur, and variation itself is apparently always a very slow process. The process will often be greatly retarded by free intercrossing. Many will explain that these several causes are amply sufficient wholly to stop to the action of natural selection." Charles Darwin, Origin of Species 1st edition (on Kindle)
One of the criticisms of Darwin was that any favorable mutation would be diluted in the next generation by blending. So for example, if a mutation caused an organism to be 50% taller, it's offspring would be 25% taller because they mated with a normal height. The grandchildren would be 12.5% taller for the same reason and so on until the original mutation was gone. Now, given the particulate theory of inheritance we know that blending is not how it works but alleles are passed on.
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