stabilizing selection(maintenance evolution, normalizing selection) Natural selection that selects against extremes at either end of the range of phenotypes (e.g. in humans babies with low or high birth weights are less likely to survive than those with a birth weight close to 3.4 kg). It occurs in environments that change little from one location to another or over time. Compare directional selection and disruptive selection.

stabilizing selection (maintenance evolution, normalizing selection) The stabilizing influence of natural selection in an environment that changes little in space and time. It tends to inhibit evolutionary innovation, and accounts for the fact that many fossil groups changed very little over long periods of time. Compare DIRECTIONAL SELECTION and DISRUPTIVE SELECTION.

stabilizing selection (normalizing selection) Natural selection that acts to maintain the constancy of a species over successive generations. It involves selection against the extremes of the range of phenotypes for a particular characteristic. For example, babies whose birth weight is substantially below or above the average of 3.6 kg historically have a greater mortality than babies of average birth weight (although medical advances have now greatly reduced this pattern of selection in humans). Compare directional selection; disruptive selection.

stabilizing selection See MAINTENANCE EVOLUTION.