Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A number of psychologists have begun to apply principles from evolutionary biology to their domains in an attempt to provide an integrated model of human behaviour. One such application, a theory based on the r/K continuum of reproductive strategies, postulates that a single heritable reproductive dimension underlies a broad range of individual differences in life histories, physiological functioning, and social behaviour (Rushton, 1985). The two experiments reported here provide a test of this theory. Experiment 1 was conducted to determine if such a reproductive dimension exists and the extent of its heritability. Numerous reproductive and other variables from a sample of 7620 twins were subjected to principal component analyses. The obtained solutions for both male and female twins revealed factors which resembled the proposed dimension. Comparisons of aggregated standard scores for monozygotic twin pairs and same-sexed dizygotic pairs indicated that the dimension was moderately heritable. The second experiment replicated and extended the first study using a broader range of variables from a sample of 250 university undergraduates. In both experiments, strongest support for the theory was found for the physiological and sexual-reproductive variables, with the findings for personality variables being less supportive. The results were generally interpreted as providing initial support for the application of r/K theory to humans.



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