 Fisher's fundamental theorem of natural selection

Fisher's Fundamental Theorem of Natural Selection, proposed by the geneticist and statistician Ronald A. Fisher in his 1930 book "The Genetical Theory of Natural Selection," states that the rate of increase in fitness of a population is proportional to the genetic variance in fitness within that population. In simpler terms, the theorem posits that: 1. **Fitness** refers to an organism's ability to survive and reproduce in its environment, which can be influenced by genetic factors.