The second evolutionary conjecture is that mutations are good. Evolutionists believe that lower forms of life had mutant children that were more fit for survival, and became dominant. If Charles Darwin had read Gregor Mendel's 1866 paper describing the results of his experiments with peas, he might not have come to the conclusion he did. But the importance of Mendel's work wasn't recognized until 1900. Today we know much more about heredity than even Mendel did, and have put this knowledge to practical use breeding horses, dogs, and pigeons.
Pigeons are a good example.
There are people who know how to breed pigeons to obtain unusual colored feathers. You can breed pigeons for generations and all you ever get are pigeons. Pigeons with unusual colored feathers, perhaps, but they are still pigeons. If these pigeons are allowed to breed indiscriminately, the offspring quickly revert to normal colors. That is because they obtain these usual colors by mating birds which lack dominant genes that would suppress the desired color.