A global carbon and nitrogen isotope perspective on modern and ancient human diet

Abstract

Stable carbon and nitrogen isotope analyses are widely used to infer diet and mobility in ancient and modern human populations, potentially providing a means to situate humans in global food webs. We collated 13,666 globally distributed analyses of ancient and modern human collagen and keratin samples. We converted all data to a common "Modern Diet Equivalent" reference frame to enable direct comparison among modern human diets, human diets prior to the advent of industrial agriculture, and the natural environment. This approach reveals a broad diet prior to industrialized agriculture and continued in modern subsistence populations, consistent with the human ability to consume opportunistically as extreme omnivores within complex natural food webs and across multiple trophic levels in every terrestrial and many marine ecosystems on the planet. In stark contrast, isotope dietary breadth across modern nonsubsistence populations has compressed by two-thirds as a result of the rise of industrialized agriculture and animal husbandry practices and the globalization of food distribution networks.

Keywords: diet; isoscape; isotope; trophic.

Fig. 1.

(Main) δ¹³C_MDE and δ¹⁵N_MDE of modern subsistence and nonsubsistence individuals plotted as ellipses representing the population μ (ellipse center) and 2σ (ellipse extent). Vegans/vegetarians within the modern nonsubsistence category are highlighted by green-shaded ellipses. The modern nonsubsistence data are plotted on an expanded scale by region in SI Appendix, Fig. S1. (Side) Bagplots of δ¹³C_MDE and δ¹⁵N_MDE pairs for PHB individuals (gray circles on the main panel) within cold C₃, arid C₃/C4, and humid C₃/C₄ environments. Black contours enclose the central 50% of individuals, and colored contours enclose the central 95% of individuals. The modern nonsubsistence data are plotted on an expanded scale by region in SI Appendix, Fig. S1. Both PHB and modern subsistence data points are plotted in SI Appendix, Fig. S2. Isotope values are reported relative to the international reference scales of Air for nitrogen and Vienna PeeDee Belemnite (VPDB) for carbon.

Fig. 2.

Modern diet equivalent data for all PHB individuals (gray points) representing the full dietary spectrum. Terrestrial (green) and Marine (blue) plant/animal δ¹³C_MDE and δ¹⁵N_MDE ranges are given (solid lines) for comparison. Dashed arrows indicate where tropic enrichment (TE) extends this range to higher values. The marine range for primary production taken from ref. for nitrogen and ref. for carbon. The terrestrial range of values for primary production are also shown for carbon (29, 30, 32, 72) and for nitrogen (27, 29, 31).