The Fundamental Theorem of Natural Selection: A Persistent Puzzle for Population Genetics
A new perspective article revisits the utility of R.A. Fisher’s Fundamental Theorem of Natural Selection, a cornerstone of evolutionary theory. While acknowledging the mathematical complexities that have long surrounded its interpretation, the author argues the theorem retains significant biological value. Its key prediction—that additive genetic variance for fitness should be depleted in populations at evolutionary equilibrium under selection—poses a profound and unresolved question for modern evolutionary biology. The persistence of high levels of additive variance in fitness components in natural populations, despite this theoretical expectation, highlights a critical gap in our understanding of the genetic architecture of adaptation.
Why it might matter to you: This analysis directly challenges a core assumption in population genetics and quantitative genetics models you may rely on. It refocuses attention on the enigmatic sources of genetic variation that fuel adaptive evolution, suggesting that current models may underestimate the role of non-additive genetic effects or the constant disruption of equilibrium by environmental change. For your work in evolutionary biology, this underscores the need to critically evaluate the genetic parameters used in predictions about selection responses and population persistence.
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