Abstract

In this study, different concepts from behavioral ecology, cognitive, developmental and personality psychology are integrated. The aim of the empirical part is to show how and why childhood context variables like social status of the father and birth rank are predictive for life span development while controlling for age and gender. This is reached by selfdevellopped instruments, which were constructed for that aim and were validated cross-culturally*.
Results of a sample of 208 family members from 86 families from Osnabrück (West-Germany) show that aversive childhood experiences, bad economic conditions in childhood and absence of younger siblings lead to an acceleration of somatic development. Critical life events like the early loss of a parent in the early years of life can lead to riskprone reproductive decisions in adulthood, because these events are seen as indicators of an unpredictive and unfavourable future. One can afford to take his/her time in leaving the parental home if life conditions are good, and one can only afford to be cautious if there seems to be time enough to do so. Birth order effects hint at intrafamilial differences in psychological as well as somatic development.
For cross-cultural comparisons these results point at the danger of misinterpreting differences in cross-cultural samples as differences in "culture" if birth order or family constellation effects are not controlled. Therefore, future studies should consider the evolutionary function of birth order effects for individual development more closely.