Summary

Adaptation implies changes in the human phenotype induced through interaction with the environment. There are four different levels of adaptation: acclimatization, plasticity, population structure and natural selection. The different levels of adaptation are active on different timescales. The present analysis concentrates on effects of plasticity and population structure using data on the stature of Danish males from archaeological and written historical sources. These levels of adaptation operate on a timescale of individual lifespan and across several generations of individuals.

The genealogical relations among the men forming the material cannot be specified. Consequently, data cannot be analysed along the lines of ordinary quantitative genetics. The focus of the analysis must be changed from individuals to groups of individuals. In this change the regression analysis is changed to an analysis of variance (ANOVA). Two groups are defined based on the conditions of living and growing; two other groups are based on the population structure in the communities from which the analysed samples were taken. The first two groups have been classified as either permissive (i.e. living in a community with good conditions) or restrictive. The second set of groups are classified as either inbred or outbred.

The stature of a mother has been shown to affect the stature of her offspring in a nonlinear way. This maternal effect is likely to postpone the effect of changes of the population structure and/or the conditions of living on stature by at least one generation. Consequently, only data extracted from populations assumed to have lived under fairly constant conditions and with a constant structure for several generations are analysed. Data have been drawn from measurements of stature in the graves of two mediaeval cemeteries and from the medical examination of young men prior to conscription.