Fisher's Theorem

Fisher's theorem, often referred to as Fisher's Fundamental Theorem of Natural Selection, states that the strength of natural selection is directly related to the genetic variance in a population. In simpler terms, when a species has a lot of genetic diversity, evolution can occur more efficiently because advantageous traits can spread more quickly through the population. Conversely, if there is little genetic variation, adaptation to changing environments becomes slower. Essentially, the theorem highlights the importance of genetic variation for the survival and evolution of species.