Dietary breadth since the advent of industrial agriculture

Most human populations currently consume a restricted diet, compared with a century ago, a study finds. The carbon and nitrogen isotope composition of human tissues can provide clues to past and present diets and food webs. To directly compare the diets of modern and ancient humans, Michael Bird and colleagues collated isotope compositions of collagen, hair, and nail keratin from three populations dating to before and after the manufacture of industrial fertilizer in 1910. The authors converted the data to a common reference frame termed modern diet equivalent (MDE) isotope (δ13CMDE and δ15NMDE) values. For modern individuals consuming a traditional subsistence diet, δ13CMDE values ranged from -30.1‰ to -11.7 ‰, and δ15NMDE values ranged from -1.8‰ to +15.1 ‰. These values imply a diverse diet covering multiple trophic levels and largely overlapped with those from samples dating to before 1910. By contrast, tissue from modern urban individuals consuming a globalized diet had δ13CMDE values ranging from -24.2 ‰ to -18.7 ‰ and δ15NMDE values ranging from +0.45 ‰ to +5.7 ‰. According to the authors, the compression of dietary breadth by two-thirds for most modern human populations may be due to the rise of industrialized agriculture and animal husbandry practices as well as the globalization of food distribution networks.

Article #20-24642: “A global carbon and nitrogen isotope perspective on modern and ancient human diet,” by Michael I. Bird, Stefani A. Crabtree, Jordahna Haig, Sean Ulm, Christopher Wurster

MEDIA CONTACT: Michael Bird, James Cook University, Cairns, AUSTRALIA; tel: +61 7 4232 1137; email:

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