Social ordering in human society is associated with gradients of disease, with an increasing frequency of mortality and morbidity as one descends the scale of socioeconomic status, which reflects both income and education. Although the causes of these gradients of health are very complex, they are likely to reflect, with increasing frequency at the lower end of the scale, the cumulative burden of coping with limited resources and stressors as well as differences in lifestyle, and the resulting allostatic overload that this burden places on the physiological systems involved in adaptation and coping.