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normalizing selection
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Diagram illustrating three types of natural selection-stabilizing, directional, and diversifying-showing how each affects the distribution of beetle phenotypes in a population over multiple generations. Shaded areas indicate phenotypes selected against, and arrows show shifts in population traits.
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normalizing selection

genetics
Also known as: centripedal selection, stabilizing selection
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Diagram illustrating three types of natural selection-stabilizing, directional, and diversifying-showing how each affects the distribution of beetle phenotypes in a population over multiple generations. Shaded areas indicate phenotypes selected against, and arrows show shifts in population traits.
Types of natural selection Three types of natural selection, showing the effects of each on the distribution of phenotypes within a population. The downward arrows point to those phenotypes against which selection acts. Stabilizing selection (left column) acts against phenotypes at both extremes of the distribution, favoring the multiplication of intermediate phenotypes. Directional selection (center column) acts against only one extreme of phenotypes, causing a shift in distribution toward the other extreme. Diversifying selection (right column) acts against intermediate phenotypes, creating a split in distribution toward each extreme.

Normalizing selection, also known as stabilizing selection, is a type of natural selection where individuals with intermediate phenotypes are favored, while extreme phenotypes are selected against. This process helps maintain the status quo of a population's traits from one generation to the next.1

For example, in humans, infants of intermediate size have a higher survival rate than those who are very small or very large. Stabilizing selection is common and can occur even after artificial selection has been applied; if artificial selection stops, natural selection will often revert traits back to their intermediate values. This leads to a steady genetic constitution within populations, a phenomenon known as genetic homeostasis.1

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2 Britannica Sources
  1. evolution - Stabilizing selection
  2. heredity - Selection

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