Paleoproteomic evidence reveals dairying supported prehistoric occupation of the highland Tibetan Plateau

Abstract

The extreme environments of the Tibetan Plateau offer considerable challenges to human survival, demanding novel adaptations. While the role of biological and agricultural adaptations in enabling early human colonization of the plateau has been widely discussed, the contribution of pastoralism is less well understood, especially the dairy pastoralism that has historically been central to Tibetan diets. Here, we analyze ancient proteins from the dental calculus (n = 40) of all human individuals with sufficient calculus preservation from the interior plateau. Our paleoproteomic results demonstrate that dairy pastoralism began on the highland plateau by ~3500 years ago. Patterns of milk protein recovery point to the importance of dairy for individuals who lived in agriculturally poor regions above 3700 m above sea level. Our study suggests that dairy was a critical cultural adaptation that supported expansion of early pastoralists into the region's vast, non-arable highlands, opening the Tibetan Plateau up to widespread, permanent human occupation.

Fig. 1.. The distribution of modern land use on the Tibetan Plateau.

(A) Map shows the distribution of modern grassland/pasture (green) and cropland (red) (text S1). The dashed square shows the study region of the barley hypothesis paper (9). Triangles display published sites with domesticated animal remains for different time periods (dataset S1). (B) Left: Percentage of total land area constituted by different elevation ranges on the plateau. Right: Relative proportion of modern cropland and grassland at different elevations of the plateau (table S1).

Fig. 2.. Map, chronology, and elevation of samples included in this study and protein results for studied individuals.

(A) Distribution of sites investigated in the present study and preservation of milk and oral proteins for individuals from those sites (table S2 and datasets S2 and S3). (B) Timeline and elevation of studied samples, total number of human individuals from each site, and protein preservation and dairy recovery from their calculus (text S2 and dataset S2).

Fig. 3.. Proteomic evidence of dairy products in dental calculus from the interior Tibetan Plateau.

Timeline and altitude of individuals whose calculus produced dairy peptides, together with information about their age, sex, and the taxa identified (confident attribution of animal species shown in black and indistinguishable species shown in gray) (details in Materials and Methods, “Protein identification” section; table S4).

Fig. 4.. Representative individuals with milk consumption evidence.

(A) MS/MS spectra of a goat BLG peptide from the earliest individual from whom dairy peptides were recovered (DA793; cal. 1500 to 1312 BCE). (B) Highest altitude individual in this study (DA742; cal. 601 to 758 CE; 4654 masl), from the Ounie cemetery in northern Tibet, accompanied by cattle/yak (Bovinae) and sheep/goat (Caprinae) bones (photograph by Z.C.).