In science, we refer to this movement as gene flow

In science, we refer to this movement as gene flow. All four of the processes represented by our fingers can cause evolution. Small population size, non-random mating, mutations and gene flow. However, none of them lead to adaptation. Natural selection is the only process that creates organisms better adapted to their local environment.I use the thumb to remember this process.Nature votes thumbs up for adaptations that will do well in their environment,and thumbs down to adaptations that will do poorly.