Molecular biologist Chao-Qiang Lai of the Jean Mayer U.S.
Department of Agriculture Human Nutrition Research Center on
Aging at Tufts University answers. This question can be
rephrased as: "How much variation (difference between
individuals) in height is attributable to genetic effects and
how much to nutritional effects?" The short answer to this
question is that about 60 to 80 percent of the difference in
height between individuals is determined by genetic factors,
whereas 20 to 40 percent can be attributed to environmental
effects, mainly nutrition. This answer is based on estimates of
the "heritability" of human height: the proportion of the total
variation in height due to genetic factors. Human height is a
quantitative, or metric, trait, i.e., a characteristic that is
measured in quantity, and is controlled by multiple genes and
environmental factors. Many studies have estimated the
heritability of human height. Often, these studies determine
heritability by estimating the degree of resemblance between