"Fitness" behaviors and anthropometric characters for offspring of first-cousin matings.

Abstract

The purpose of this article is to describe a unique inbreeding study and to discuss the effects of first-cousin matings on polygenic, multifactorial characters. Francis Galton collected behavioral and anthropometric data on a large sample of individuals in Victorian England over 100 years ago. These data permit control of possible effects of socioeconomic status bias in inbreeding studies. The measures included variables apparently related to fitness, such as visual and auditory acuity, as well as anthropometric characters. On the average, the mean of the inbred group is one-tenth of a standard deviation lower than the mean of the control group for the behavioral as well as the anthropometric characters. These results are consistent with those of other inbreeding studies of cognitive abilities and birth characteristics. Mean differences of this magnitude are to be expected given a polygenic and multifactorial system of inheritance. Samples greater than 1000 in each group are required to detect such differences reliably at statistically significant levels. It is puzzling that characters which would be assumed to have been subjected to strong directional selection, such as visual and auditory acuity, show no greater inbreeding depression than other characters.