8 - Seasonal effects on physical growth and development

Summary

As auxologists know, le Comte de Montbeillard measured his son's height every six months between 1759 and 1777. Buffon, who reported the findings (Tanner, 1981), noticed that the son grew twice as much in the summer as in the winter; this was probably the first description of a seasonal component to growth. The subject has remained a firm favourite among auxologists ever since, with a substantial literature dating back more than a century (e.g. Malling–Hansen, 1886; Orr & Clark, 1930). The early studies were European, but North Americans made an increasing impact from the beginning of this century (E.L. Marshall, 1937), and seasonality of growth in the developing world has been documented since the middle of this century (see Valverde et al., 1972, for a comprehensive review).

Seasonal trends in growth are very different in the developed world and the developing world, so it is important to distinguish between them. In the developing world growth rate is very clearly related to climatic factors associated with the timing of the rainy season or seasons, through their influence on food availability, parasite load (e.g. malaria) and infection. The absence of a rainy season in most parts of the developed world means that the most obvious seasonal influences do not apply, so that seasonality of growth is much more subtle. However, this is not to say that factors such as infection have no effect on growth in the developed world - they are just harder to identify.