Environment and secular changes in modern man.

The secular trend of human traits has so far been investigated mostly with respect to the morphological traits, mainly stature and body weight. However, some studies of changes in the physiological and psychomotor traits have also been published. The intergenerational changes concern changes in the development rate, magnitude of traits and sequence of symptoms of development. These changes are mainly due to changes in the environmental conditions, particularly of the living conditions. Another factor--though increasingly less expressed in present-day man--consists of genetic determination (especially survival). Migrations changing the gene frequency in populations represent the third factor. In the major part of economically developed countries interpopulational changes continue; in highly industrialized countries no further acceleration of sexual maturation takes place. Some studies from India and certain African countries point to a regression of physical development in children. Since stature and body weight are positive indices of health, they are important from the epidemiological standpoint and should be closely analyzed. This paper describes the findings obtained hitherto in studies performed in Poland or resulting from an analysis of materials from various countries.