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

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 13,533 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 between ancient and modern human diets and the natural environment. This approach reveals a broad diet in ancient times, 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, dietary breadth across modern non-subsistence populations has dramatically compressed by two-thirds, largely as a result of the rise of industrial agriculture and animal husbandry practices, as well as the globalization of food distribution networks.