Thesis Spotlight: Eli Visio (Proteomic Analysis of Equine Milk Consumption)

Milk Roads: A Proteomic Analysis of Equine Milk Consumption in Central Asia’s Agro-Pastoral Societies

This study explores the patterns and frequency of horse and ruminant milk consumption among pastoral communities within Kazakhstan, Uzbekistan, the Russian Federation, Mongolia, and Kyrgyzstan between the 8th and 15th centuries CE. While horses are well understood through their contributions to mobility and warfare within Inner Asia, their impact on everyday subsistence is less clear. The project is placed within the context of the Silk Road, a network of trade routes and regions critical to human development that linked China, Central Asia, the Middle East, and Europe from the 2nd century BCE to the 16th century CE. It seeks to generatively contribute data to the question of how ancient populations subsisted in this ecologically diverse region. The project is based on a Liquid Chromatography Tandem Mass Spectrometry investigation of dairy proteins preserved within dental calculus. Protein extraction and analysis via LC-MS/MS will identify the presence or absence of dairy proteins and the species they come from. The primary questions to be evaluated are: What types of dairy were consumed, if any, and in what quantities? Do the kinds of dairy consumption and intensity vary by ecological regions or points in time? What is the relationship between the consumption of horse dairy, the chronology of horse domestication, and the relationship between animal management and mobility across Inner Asia?

This project seeks to contribute to understanding the history of  dairy consumption in Asia and to help address the scarcity of direct evidence on equine milk. Specifically, it contributes to underdeveloped datasets documenting the time dairy consumption emerged, and the regions the practice emerged. Current biomolecular evidence suggests that horse milk consumption only became prevalent in the archaeological record more than a millennium after domestication and thousands of kilometers east of where the earliest horse cultures began, creating an interesting puzzle. The differences in geography and timing make it difficult to determine how fast dairying developed alongside horse management and mobility. Current approaches  for identifying dairy consumption often rely on characterizing the carbon isotopes of milk fats in pottery, but this can be challenging to apply to horse milk. Unlike for ruminants, the adipose and milk fats of equids are isotopically highly similar, and pottery can also be reused—meaning that many different fats may be mixed together, thus giving a mixed signal. Proteomic investigations get around these problems and have the added advantage of being highly species-specific. This project investigates the milk protein β-lactoglobulin, which preserves in the dental calculus (calcified dental plaque) of ancient people, and its detection provides a highly individualized picture of milk consumption in the past. 

The broader goal of this study is to better understand horse milking’s connection to past and present subsistence systems. The consumption of dairy is still an integral part of modern-day subsistence; pastoralism remains a critical lifeway today. Because dairy products allowed mobile herders to survive in areas where agriculture wasn’t ecologically feasible, pastoralism can be viewed as an adaptation that influenced how many modern communities sustain themselves today. By evaluating the history of horse and ruminant dairying, this study aims to understand past and present connections between mobility, the environment, and human subsistence throughout Central Asia. Understanding when horse dairying began and how common it was is key to understanding both the economic importance and cultural meaning of horse-human relationships on the steppe in the past and their impact on modern society.