The saltation theory came about by Hugo deVries (!848-1935) who was a Dutch botanist working with primroses. He believed a new species had suddenly sprung into existence as a mutation. He theorized that new species "saltated" (leaped), that is continually spring into existence.
This was a new idea; and, during the first half of the 20th century, many evolutionist biologists, finding absolutely no evidence supporting "natural selection", switched from natural selection (Darwinism) to mutations (Neo-Darwinism) as the mechanism by which the theorized cross-species changes occurred in order to prove the mutation theory, deVries and other researchers began experimentation on fruit flies with no avail. There has not been one success story in producing new species. Mutations cannot produce evolution. They are always harmful.
Richard Goldschmidt of the University of California spent most of his adult life trying to prove that fruit flies could change into new species, but without success. "After observing mutations in fruit flies for many years, Goldschmidt fell into despair. The changes, he lamented, were so hopelessly micro (small) that if a thousand mutations were combined in one specimen, there would still be no new species." (Norman Macbeth, "Darwin Retried" (1971), p.33).
Gregor Mendel and his astounding research findings about heredity, in which his genetic research has repeatedly confirmed that there are only changes within species. There is never cross-species changes (which would be true evolution). This is true of plants, animals, and even microbes.
When God created plants and animals, He created them to reproduce "after their kind". A cat cannot reproduce with a dog to make a "cat-dog". Neither can a fish reproduce with a bird. In I Corinthians 15:39, the Scripture says, "All flesh is not the same flesh; but there is one kind of flesh of man, another flesh of beasts, another of fishes, and another of birds." You can plainly see that there is four distinct categories of animal flesh and each reproduce within their kind. Mutations within each kind usually results in early death of the organism. Man is still man. I have not seen a four-legged man or a man with wings of a bird, have you! Man is getting weaker not stronger as evolution would have you to believe. But man will change one day. People who know the Lord as personal Saviour will one day have a changed glorified body (I Corinthians 15:51-57). What a glorious day that will be!