The outcome of this work was the recognition that the force of natural selection was often much stronger than had been appreciated . Many ecogenetic situations ( such as polymorphism ) were not selectively neutral , on the contrary , they were maintained by the force of selection . The outcome of this work was the general recognition that the force of natural selection was often much stronger than had been appreciated before , and that many ecogenetic situations ( such as polymorphism ) were not selectively neutral , they were maintained by the force of selection .