Stabilizing Selection in Natural Populations: Examples from Human Birth Weight and Peppered Moths in England

stabalizing selection

natural selection that favors average individuals in a population; results in a decline in population variation

Stabilizing selection is a type of natural selection that favors the individuals in a population that have intermediate traits. This means that individuals with extreme traits are less likely to survive and reproduce, while individuals with traits closer to the population average are more likely to have offspring.

A classic example of stabilizing selection can be observed in human birth weight. Babies born with extremely low or high birth weights are less likely to survive than babies with intermediate birth weights. This has led to stabilizing selection, where the optimal range for human birth weight is between 6-8 pounds.

Another example of stabilizing selection can be seen in the color of peppered moths in England during the Industrial Revolution. Prior to the Industrial Revolution, the majority of the moths in England were light-colored. However, when the industrialization resulted in pollution and darkened the environment, the dark-colored peppered moths had better camouflage and were less likely to be preyed upon by birds. This led to an increase in the population of dark-coloured moths, while the population of light-colored moths declined. However, once pollution decreased and the environment became lighter, the population of light-colored moths again increased. Through this process, stabilizing selection selected for the intermediate range of moth colors, i.e., moths that were a mixture of light and dark colors.

Overall, stabilizing selection helps to maintain the status quo in a population by selecting for individuals with intermediate traits. This process helps to maintain the genetic diversity within a population while also allowing it to adapt to changing environmental conditions.

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