Sex ratios and the r/K continuum /

Abstract

An analysis of existing U.S. Census, Uniform Crime Report and Vital Statistics data was undertaken to determine whether a relationship exists between environmental factors, specifically sex ratios, and population behavior. Nine U.S. states were examined for their ratios of men to women, and then compared to existing data concerning marriage rates, birth rates, rates of birth to un-wed mothers, and violent crime rates The theoretical framework for this research was based on the r/K continuum, a biological theory focused on reproductive strategy and resource allocation of individuals within a population. Pearson's Correlation coefficients were calculated in order to find the strength, direction, and significance of any linear relationship between the variables. Four hypotheses were tested in this way: Hypothesis One: Since high birth rates are more indicative of the r end of the continuum and low sex ratios represent an r-selected population, there should be a statistically significant (a < .05) negative correlation between birth rates and sex ratios; Hypothesis Two: Since r-selected populations exhibit higher rates of birth to un-wed mothers, and low sex ratios represent an r-selected population, there should be a statistically significant (a < .05) negative correlation between rates of birth to un-wed mothers and sex ratios; Hypothesis Three: Since higher ratios of married to unmarried people suggest a K-selected population, and higher sex ratios represent a population at the K end of the continuum, there should be a statistically significant (a < .05) positive relationship between marriage ratios and sex ratio; and Hypothesis Four: Since high violent crime rates are associated with an r-selected population, and low sex ratios represent a population at the r end of the continuum, there should be a statistically significant (a < .05) negative correlation between violent crime rates and sex ratios. The results of the statistical analysis supported only Hypothesis Two; there was a statistically significant inverse relationship between sex ratios and rates of birth to un-wed mothers. The results of the study showed general support for the evolutionary theory of human behavior, as the trends revealed by the correlation coefficients demonstrated the expected outcome. However, the trends were not statistically significant and, therefore, the remaining hypotheses were rejected.