New Faculty: Elizabeth (EA) Quinn
by EA Quinn

Infant formula choices abound in the Philippines, as shown in this photograph taken in a grocery store in Cebu City, Philippines, in 2007.

EA Quinn trains field staff at the Office of Population Studies, University of San Carlos, in minimally invasive fingerprick biomarker collection methods.

For much of human history, the first food infants received was human milk. Although the archaeological and historical record have available examples of artificial feeding, this was comparatively rare. Artificial infant formulas, which did not come into common use until the 1950s, are currently a multibillion-dollar-a-year industry. Despite the public health mantra "breast is best," most infants in the United States and abroad are not breastfed for the recommended four to six months (American Academy of Pediatrics; World Health Organization). Additionally, the actual composition of milk, and the way maternal physiology, genetics, diets, and ecological factors may contribute to this variation, are relatively understudied. Both breastfeeding behaviors and human milk composition have been largely the purview of nutritionists and public health researchers, with environmental and evolutionary dimensions missing from analyses.

Why then, given the central role milk has played in human (and mammalian) evolutionary history, have anthropologists paid so little attention to it? Breastfeeding has been investigated in some depth, but human milk, as a natural part of human biological variation, remains comparatively understudied. Breast milk is, in fact, highly variable in composition, with the greatest variation between women in the same population although there is considerable variation between populations as well. The underlying physiological factors that predict these differences are poorly understood. My immediate work focuses on milk macronutrients (fat, protein, carbohydrates), calories, and fatty acids with future work expanding to milk hormones and immunological proteins. In my research, I have found additional evidence for an independence of milk macronutrients from the mother's diet or body composition—how much she eats or what she eats does not dramatically influence the fat, protein, or energy in her milk. However, the mother's diet is an important determinant of the fatty acids in her milk, especially the omega-3 and omega-6 fatty acids important for infant neurological development, brain growth, and weight gain.

My work adds to this growing body of knowledge by specifically taking a life course and developmental approach to human biology, especially reproductive investment. My prior research has investigated these questions in a birth cohort of 1,100 women born from 1983-1984 in Cebu, Philippines, and followed bimonthly from birth to two years and every two or three years afterward. These infants are now adult women having their own children. My research specifically works with these two generations, specifically looking at how milk composition, breastfeeding, reproductive behaviors, and reproductive investment are influenced by the mother's own infancy and childhood characteristics.

Future work will expand these preliminary analyses in two directions. The first direction will look at longitudinal changes in milk composition over the first year of lactation. As part of this research, I will be looking at correlations of growth between generations, with milk composition and hormones as possible co-factors mediating these correlations. The second direction will be a cross-population comparison of breast milk composition and hormones under different ecological conditions. Understanding how ecology may influence milk composition, along with maternal development in diverse ecologies, will provide insights into evolutionary pressures on human lactation.

As part of my research, we will be establishing a new lab in the anthropology department focused on studies of human biology and health using minimally invasive, field-friendly techniques for studying biomarkers. This will include the development of hormonal assays to look at reproductive and metabolic hormones in mothers and infants in blood, saliva, urine, and breast milk. I'm particularly interested in developing field-stable methods for studying breast milk hormones and composition. I am teaching Developmental Plasticity and Human Health, where we discuss many of these themes in a comparative, population-based perspective. I hope to offer future courses on reproductive endocrinology and lab-based methods courses in human biology research.