ABSTRACT
According to life history theory, human behavior and biology are shaped by natural selection throughout the life course to maximize biological fitness, which is often measured as the number of surviving offspring. Infancy has likely been an immunologically risky time throughout human evolutionary history. Risks are currently most pronounced in many of the world's less-affluent regions due to environmental pathogenicity and limited food and monetary resources. A number of changes transpired during this period. A water piping system was installed in 1998, further decreasing the energetic costs of water hauling for women. Several small stores have opened, facilitating village-wide increases in soda consumption. To evaluate the time cost of breastfeeding, we compare observed patterns of maternal employment and agricultural and domestic labor over time. Yucatec Maya women continue to practice prolonged and intensive breastfeeding, despite a number of changes in energetic and epidemiologic conditions over time.
