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Evolution of Sex and the Lottery Principle

QUESTION: Evolution of Sex and the Lottery Principle


The Lottery Principle was first proposed by the American biologist George C. Williams, and suggests that sexual reproduction introduced genetic variety in order to enable genes to survive in changing or novel environments. The concept’s name derives from a lottery analogy invoked to get across the concept that breeding asexually would be like buying a large number of tickets for a national lottery but giving them all the same number. Conversely, sexual reproduction is like purchasing a small number of tickets but giving each of them a different number.

The Lottery Principle suggests that since sex introduces variability, organisms would have an improved chance of producing offspring that will survive if they reproduce a range of types rather than merely more of the same. Asexual reproduction is poorly equipped to adapt to rapidly changing conditions because the offspring are essentially clones of the parents and therefore possess less genetic variation.

Evolution of Sex and the Lottery Principle - The difficulty
It is the diversity of the species, the principle states, which allows an organism to maintain its competitive edge in the struggle for survival. The difficulty lies in the fact that it suggests that sex would be favored by a variable environment, yet a close inspection of the global distribution of sex reveals that where environments are stable (for example, in the tropics), sexual reproduction is most common. Conversely, asexual reproduction is most common in areas where the environment is unstable (for example, at high altitudes or in small bodies of water).

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