There can be some confusion on the definition, and often evolution is equated with natural selection, However, selection doesn’t actually need to occur for muta

There can be some confusion on the definition, and often evolution is equated with natural selection, However, selection doesn’t actually need to occur for mutations to be considered evolution. One definition of evolution is “change in the heritable characteristics of biological populations over successive generations” Mutations that effect phenotype (heritable characteristics), may not confer either an immediate advantage nor disadvantage, but we can still witness evolution in terms of increased (or decreased) diversity. Sometimes selection pressure on that diversity may not occur for some time. Take for example two very differently sized and separate breeding populations of a species. The larger breeding population will tend to harbor more mutations generating new phenotypes, than the smaller one. When selective pressure then is exerted on both populations, the larger population will often fair better. So did the “evolution” occur before or after the selection pressure. It’s valid to say the evolution occurred before, since we can measure the differences between the populations and see a difference even before the selection. This mechanism is called genetic drift and is an important part of evolution. https://en.m.wikipedia.org/wiki/Genetic_drift https://en.m.wikipedia.org/wiki/Genetic_drift On the other end, mutations that don’t effect phenotype, ie that can’t have a selective advantage or disadvantage usually aren’t even worth talking about, they’re generally noise (think junk DNA). Edit: And genetic drift is actually an incredibly important reason why masking is so important and helpful. Limiting the replication of the virus means that on top of saving people, we are limiting the genetic variability that will begin to occur in larger rapidly mutating populations, even ones that aren’t facing specific selection pressure. So when we do put a strong selection on them with a vaccine, we prefer to do it on the smallest population we can.