Stabilizing
Selection on birthweight in humans
Karn & Penrose (1951) showed that
birth weight follows a normal distribution, that mortality for newborns
is greater for those either under- or over-weight, and that the mean
birth weight (7 lbs) coincides with that showing minimum mortality.
That is, natural selection reduces the variance in birthweight, in such
a way that the
distribution has become stabilized around the optimum size for maximum
survival.
Text
material
© 2004 by Steven M. Carr