Stabilizing selection (also called balancing selection) favors the middle ground — that is, traits that aren't too hot or too cold, but just right, when just right means comfortably in the middle between two extremes. Think of this form as the Goldilocks of selection.
In stabilizing selection, the most-fit trait is intermediate with respect to whatever characteristic selection is acting on. An example is the birth weight of babies. Very small babies have a lower probability of survival, but very large babies are more likely to suffer complications during birth. Babies of intermediate size, however, are most likely to survive to reproduce.
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