Current evolutionary adaptiveness of anxiety: Extreme phenotypes of anxiety predict increased fertility across multiple generations.

OBJECTIVE: Although recent research has begun to examine the impact of elevated anxiety on evolutionary fitness, no prior research has examined anxiety across a continuum. Such research is important as the effect of traits across a continuum on fertility hold important implications for the levels and distribution of the traits in later generations.

METHOD: In a three-generational sample (N = 2657) the linear and quadratic relationship between anxiety and the number of children, grandchildren, and great-grandchildren 15 years later was examined.

RESULTS: The findings suggested that anxiety had a positive quadratic relationship with the number of children, grandchildren, and great-grandchildren 15 years later. These relationships were not significantly moderated by sex. Moreover, most of the variance between anxiety and the number of great-grandchildren was explained by anxiety's influence on the number of children and grandchildren, as opposed to anxiety having an independent direct impact on the number of great-grandchildren.

CONCLUSION: These findings suggest that extreme values from the mean anxiety are associated with increased evolutionary fitness within the modern environment.