Disease diversity and human fertility

The existence of parasitic constraints on the evolution of life-history tra its in free-living organisms has been demonstrated in several plant and ani mal species. However, the association between different diseases and human traits is virtually unknown. We conducted a comparative analysis on a globa l scale to test whether the diversity of human diseases, some of them respo nsible for high incidences of morbidity and mortality, were associated with host life-history characteristics. After controlling for direct confoundin g effects exerted by historical, spatial, economic, and population patterns and their interactions, our findings show that human fertility increases w ith the diversity and structure of disease types. Thus, disease control may not only lower the costs associated with morbidity, but could also contrib ute directly or indirectly to reductions in human population growth.