Abstract
This paper presents evidence supporting the view that in the past natural fungal poisons (mycotoxins) in moldy grain strongly influenced variations in fertility and mortality rates. The poisons that influenced fertility may have reduced conceptions and increased spontaneous abortions. Those that influenced mortality may have damaged the immune system. In particular, tuberculosis, the most common cause of death, may have been a sentinel disease for immune system damage by mycotoxins. It is unlikely that any one formula (specifying the amounts of each predictor variable) will be found that can predict fertility and mortality over wide areas or long time periods. However, by using just three kinds of variables—climatic, dietetic and economic—it may be possible to predict more than half of the variation infertility and tuberculosis mortality up to 1900 in Europe and America. The evidence presented supports the view that the two principal factors influencing natural population increase in Connecticut during 1660-1900 were (1) increased consumption of potatoes and (2) improvement in transportation systems.