Data on sex differences in mortality, morbidity, growth under conditions of environmental stress, and growth responses to environmental improvement are reviewed to test the hypothesis that males are less buffered than females against the environment during growth and development. The hypothesis predicts that males should be more affected by environmental stress, and the strongest support for this is found in studies of the prenatal period. Under stressful conditions, males have higher late fetal mortality than females, and their fetal growth generally has been found to be more retarded. Investigations of postnatal responses to environmental stress have yielded much less consistent results, in large part because of the fact that male children are given preferential treatment in many societies.
Results of studies of differences between the sexes in their response to environmental improvement are contradictory. During the prenatal peroid males seem to show a greater response to nutritional supplementation, while postnatal catch-up growth is usually greater in females. Similarly, some investigations report larger secular trends in males, while others have found larger increases in females. These contradictory findings can be reconciled with the hypothesis of greater male environmental sensitivity, but they illustrate the need to obtain more specific information on the environment to which males and females are subject before the hypothesis can be tested adequately.