This is a different argument, one which I can agree with. I was specifically saying that the argument for how a species acquired a universal trait can't be "bec

This is a different argument, one which I can agree with. I was specifically saying that the argument for how a species acquired a universal trait can't be "because it didn't hurt their fitness that much", you have to have positive pressure for a trait to spread to the entire species (or it must be a trait left over from an ancestor where it had these pressures).