A change in the shape and size of young Americans' heads has been empirically observed with, specifically, a tendency toward dolicocephalic and smaller heads. It is known that hormones in food are likely to affect the growth process. In recent decades this factor distinguished the diet of Americans from the diet of Europeans. It is suggested that the general acceleration of growth in the most recent American generation could have been caused by accumulated hormonal residues in diet. The general acceleration of growth caused by hormones affects long bones more than any other tissue, and it triggers inhibitors of growth during earlier stages of flat bone development. Because of that, the relative size of the skull (flat bone structure) with respect to the body is diminished. This change of body/head proportion could be accompanied by a diminution in the absolute size of the skull as well.