Fisher's Theorem of Natural Selection Biological & Biomedical Essay (Essay Sample)

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Fisher’s Theorem of Natural Selection
One of the most commonly cited ideas in evolutionary biology is Fisher's Basic Theorem of natural selection. It has been argued, however, that the theorem's intended interpretation is somewhat different from what Fisher meant to say. Looking in a new way at a recent explanation for the evolution of clutch size will clarify what Fisher meant. In part, the controversy rises from the opposing views encouraged by other biologists.
Fisher’s remarks on average fitness, which he expresses in different ways, appear to contradict his proud arguments for his Fundamental Theorem of natural selection. The theorem states that 'an organism's rate of fitness rise over a specific period of time is similar to its genetic variance in fitness' (Wool et al. 252). In other words, Fisher would claim that 'a rise in the rate of fitness for any given species is equal to its genetic variance in fitness' (Grafen 393). If any species’ fitness is defined as average fitness, which is the basic reasoning, these declarations would mean that the species' average fitness increases gradually over time.