Paper short abstract:

Milk’s evolutionary function is to support infant growth. Bovine infants grow rapidly to large sizes, so consumption of bovine milk by human children may enhance growth and possibly accelerate maturation. I report on life history effects of bovine milk intake in children from the U.S. and India.

Paper long abstract:

The use of domesticated mammalian milk had a profound effect on human populations, as evidenced by the high frequency of the allele for lactase persistence among populations that adopted this practice. However, despite evidence for strong positive selection for this trait, the fitness benefits associated with dairy consumption beyond the weaning period are not clear. Hypotheses have included an overall increase in high quality food, or calcium in the diet, or lactose's ability to substitute for Vitamin D have been put forward, but evidence supporting any of these is scant. Alternatively, given milk's unique evolutionary function as a food to support the growth and development of nursing infants, and the fact that bovine infants grow rapidly to large body sizes, it is possible that consumption of bovine milk by post-weaning age human children could enhance growth and possibly accelerate sexual maturation. This could result in earlier or more successful reproduction, and ultimately enhanced fitness among milk drinkers. This paper reports on data indicating life history effects of bovine milk consumption among children from a large cross-sectional survey in the United States and an ongoing cohort study in Maharastra, India. The research in India provides a useful counterpoint to U.S. or European studies as milk has a deep history there and frequencies of lactase persistence show a strong cline across the subcontinent, but milk consumption occurs against a very different dietary and ecological backdrop.