One example of how natural selection can change the distribution of a trait is the peppered moths during the industrial revolution. The moths were originally mainly white with a few black spots, however, when all the factories were built, the trees the peppered moths lived on turned a black color, causing ones who were mostly white to be picked off by predators, but the ones that were black with a few white spots survived and blended in better, leaving them to breed and produce more black-colored moths that would survive easily. This shows the changing of a trait because ones that used to be mostly white were killed, showing a shift in the trait pattern in favor to the black moths that now lived instead of the white moths. (Sorry its long)
Someone can know what happened and use that against you to physically harm you. Or maybe it is like a personal thing, like prostate and you're just embarrassed about it.
