Takumi Tsutaya

Detection of breastmilk protein in an archaeological infant dog skeleton

Takumi Tsutaya§, Meaghan Mackie£, Takao Sato#, Jesper V. Olsen±, Enrico Cappellini£

§ Japan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka, Kanagawa, 237-0061, Japan; £ Natural History Museum of Denmark, University of Copenhagen, 1350 Copenhagen, Denmark; # Department of Archaeology and Ethnology, Faculty of Letters, Keio University; ± Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark

Proteomic analysis of ancient bones has previously been used to reveal phylogeny, developmental stage, and physiological status of individuals who lived in the past. These studies targeted the endogenous proteins in the bone tissues. In this study, proteomic analysis was applied to rib and vertebra of an archaeological infant dog skeleton excavated at the Hamanaka 2 site (430–960 cal AD), Rebun Island, Hokkaido, Japan. The age at death of this individual was estimated as 5–6 weeks after birth from the evidence of tooth development and eruption. Several proteins (e.g., alpha-fetoprotein and epiphycan) that are expressed exclusively in fetuses and developing infants were detected, which is consistent with the result of morphological age estimation. Furthermore, dog beta-lactoglobulin, one of the proteins that is expressed exclusively in the whey fraction of milk, was also detected. Infant dogs consume a large amount of milk (approximately 15% body weight) per day. Our results indicate that the analyzed bone remains belonged to a dog who most probably died shortly after it was fed with milk. During the decomposition of the dog’s body, the consumed milk diffused from the digestive tract and was absorbed in the bones. The results of this study indicate bone palaeoproteomic analysis can also be used to investigate exogenous protein markers (e.g., for milk consumption) and to reconstruct events occurring close to death.