Breastfeeding! Noreen Tuross and isotopes

Noreen and Marilyn about 1995

Marilyn and Noreen about 1993

         Although I’d upped my wardrobe at the Geophysical Laboratory from K-Mart specials to L.L. Bean clothing, I was certainly not fashionable. In 1978, I met visiting student Noreen Tuross who had been working with my colleague Ed Hare on amino acids in ancient bones. Noreen was getting her Masters degree from Bryn Mawr College, a fancy women’s school on the Philadelphia Mainline. We met just prior to her around-the-world trip funded by a fellowship from the Watson Foundation. Watson, one of the founders of IBM, created a foundation that recognized students from smaller schools who had big ideas for changing their science discipline. Noreen was, and still is, a visionary with respect to weaving an understanding of medical science with the study of ancient humans.

         The day we met Noreen, a natural platinum blonde, is as far away from a “dumb blonde” as you can get. She wore tall leather boots, a mid-calf skirt, and a long woolen coat, probably from a swanky department store like Bloomingdales or Garfinkels. She spent the following year climbing into caves with her new husband, Dick Waldbauer, finding saber tooth tiger and other extinct animal bones that she brought back for analysis at the Geophysical Lab.

         In 1985, Noreen had finished up a Ph.D. in medicine from Brown University and was moving with her family, including her precocious 5-year old, Jacob Waldbauer, now a Professor of Biogeochemistry at the University of Chicago, to the start a postdoc at the National Institutes of Health working on the chemistry of bone formation. I offered them a place to stay at my small house in Wheaton, MD, until they could find a somewhere to live. They moved in for a month finally buying a house a couple of miles away in Rockville. We became good friends. When Chris and I married a year later, Noreen, a trained opera singer, sang at our wedding.

         Noreen started a second postdoc at the Geophysical Lab in 1987, specializing in both modern and fossil protein studies, having training in immunology and ancient DNA methodology, as well as protein biochemistry. She wanted to investigate the nitrogen isotope fractionation between a mother and her nursing infant. This idea was important for understanding why the human population rose dramatically after the origin of agriculture. Theoretically, infants should have a nitrogen isotope composition that is slightly greater than their mothers, because “you are what you eat” plus a little bit more.

         Our hypothesis was the following: prior to a secure source of food for raising children, mothers (i.e. hunter gathers) needed to nurse their children for longer periods of time. Once food could be grown and cached, mothers (e.g. agriculturalists) could wean their children earlier, get pregnant and have more children, thus leading to a rise in population. At the time of this study, I was pregnant with my daughter Dana. We eagerly anticipated her birth. In fact, Noreen came to the hospital with a bucket of dry ice to save my placenta for “further study”, when we got old and had nothing better to do. She also came when Evan was born, so we have a replicate placenta. The placentas were kept at the Smithsonian Institution for years, and small pieces now remain in her lab at Harvard University! Dana and Evan at first were embarrassed by this fact, but now they’re proud.

         I began sampling Dana’s fingernails and mine right after she was born. The first set of fingernails was “in the bag” so to speak, but they then seemed to be growing very slowly. I would examine them every day when I returned from work. Our day care “mother” Susan Agugua was watching Dana full time. Finally, I mentioned to Susan that I was puzzled as to why Dana’s fingernails were not growing. Turns out, Susan was trimming them! Thereafter, she saved them and the study continued.

         In addition, samples were obtained from more than a dozen other mothers and their infants who were exclusively breastfed. As we predicted, we found an enrichment in nitrogen isotopes between mothers and infant pairs as we had hypothesized.  As the babies were weaned onto solid diets comparable to what their mothers were eating, the nitrogen isotope differences between mothers and babies decreased over time (Fogel et al., 1989). After babies were fully weaned, their nitrogen isotope values were the same as their mother’s.

         We then recruited Douglas Owsley, a forensic anthropologist at the Smithsonian Institution, to analyze human bones from two populations: hunter gathers from Tennessee and corn-growing Indians from South Dakota. We found that even though these two populations depended on very different sources of food, children were weaned about at the same age, roughly a year old, and their nitrogen isotope values in bones matched the adults in the population by the time they were two to three years old. The nursing effect has been measured in populations of other mammals---seals (Newsome et al., 2010), cave bears, killer whales (Newsome et al., 2009), as well as being a keystone work for anthropological investigations of ancient civilizations (Katzenburg and Waters-Rist, 2018; Xia et al., 2017). 


            The study was published in the Carnegie Institution of Washington’s Yearbook, but was never accepted at a peer-reviewed journal. Although Science magazine published a photograph of Noreen and me and wrote about our work in their news column, the paper was rejected without review because it was deemed to not be of “general interest”. The Journal of Physical Anthropology rejected the paper because a reviewer wasn’t sure the study was widely applicable to different populations. We were disappointed and frustrated that this important work was not recognized appropriately. Today, people accept our findings as important, but not everyone has read that original paper with Dana’s and my fingernail data prominently displayed in a figure.   This study is yet another example of how scientists need to stick to their ideas. If the data is good, then let time and follow up research decide if it is relevant.