The evolution of evolution from my childhood to now. Science is not settled.
In my early childhood in Sweden we lived is a small community where grades 3-6 were taught together in one class. This meant that the teacher did allow a lot of freedom to explore on my own books in the school library. They had not thrown away any old books the last forty years, so I had quite a selection of old textbooks to choose from.
One in particular caught my eye. It was about anthropology and classification of races by skull index. It was originally based on the works of the Swede Anders Retzius (1796-1860). His research was to classify old bone fragments, but his findings were now extrapolated to explain the evolution of man. There were pictures of people of all kinds of races, with the Nordic, blond and blue-eyed being the most evolved, and the black race, with some exceptions much closer evolutionary to the apes. Not only that, but since men have 40% larger brain volume than women, men are further evolved than women. Being 9 years old I believed everything, since it was in a book. I especially liked being superior to girls.
The next time evolution was taught it was the standard stuff with the horse’s hoof being a nail; fishes grew legs instead of fins and so on. We also had a lot of rudimentary organs, not only the appendix, but tonsils and tailbones too. And this time dogs can look quite different, but people are all equal, and girls are as smart as boys (especially the blond Lithuanian girl who emigrated to Canada. I had to admit she was both cute and smart).
The third time around we tackled some of the hard stuff, mutations being a necessary ingredient for evolution. I read up on radiation gardens, where we can grow superior plants, since we know that at least 10% of mutations are beneficial, just weed out the bad ones and superior plants will emerge.
The radioactive gardens are now but a memory, since it was discovered that nobody could find any positive mutations that way. The closer you got to the source, the worse it got. It turns out that positive mutations are rare indeed. The ones most commonly found are in viruses, but they are positive only from the virus’s point of view.
Survival of the fittest tends to weed out bad mutations, but does nothing to explain the mechanism for speciation creep; it tends to reinforce the speciation boundaries. The genetic code that allows adaption in species is already there, so when the changed environment occurs, we are changed accordingly. None of the mechanisms we have used to explain evolution holds up to examination. The mathematics is just not there. And a system this complicated and beautiful, where so many parts of it are at a mathematic optimum is not possible to bootstrap.
We are left with the humbling fact that we do not know the mechanisms. Yet the textbooks still explain discredited mechanisms as evolutionary facts to yet another generation of kids, thus depriving them of the wonder that there is something beyond themselves, which they can try to grasp, but realizing that there is always one more level of understanding that is beyond them.