Changing patterns of human resource use and food consumption have profoundly impacted the Earth's biosphere. Until now, no individual taxa have been suggested as distinct and characteristic new morphospecies representing this change. Here we show that the domestic broiler chicken is one such potential marker. Human-directed changes in breeding, diet and farming practices demonstrate at least a doubling in body size from the late medieval period to the present in domesticated chickens, and an up to fivefold increase in body mass since the mid-twentieth century. Moreover, the skeletal morphology, pathology, bone geochemistry and genetics of modern broilers are demonstrably different to those of their ancestors. Physical and numerical changes to chickens in the second half of the twentieth century, i.e. during the putative Anthropocene Epoch, have been the most dramatic, with large increases in individual bird growth rate and population sizes. Broiler chickens, now unable to survive without human intervention, have a combined mass exceeding that of all other birds on Earth; this novel morphotype symbolizes the unprecedented human reconfiguration of the Earth's biosphere.

Little is known about the early history of the chicken (Gallus gallus domesticus), including the timing and circumstances of its introduction into new cultural environments. To evaluate its spatio-temporal spread across Eurasia and north-west Africa, the authors radiocarbon dated 23 chicken bones from presumed early contexts. Three-quarters returned dates later than those suggested by stratigraphy, indicating the importance of direct dating. The results indicate that chickens did not arrive in Europe until the first millennium BC. Moreover, a consistent time-lag between the introduction of chickens and their consumption by humans suggests that these animals were initially regarded as exotica and only several centuries later recognised as a source of ‘food’.

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Domestic chickens (Gallus gallus domesticus L., 1758) were integrated into agricultural systems in the Horn of Africa as early as the pre‐Aksumite period (c. 2,500 years ago), after they were introduced from Asia through land and maritime trade and exchange. In this paper, we explore the development of chicken landraces in this region by examining continuity and change in chicken body size. Specifically, we compare the measurements of chicken bones dating from 800 BCE to 400 BCE from the pre‐Aksumite site of Mezber in northern Ethiopia, with those of modern chickens (of known age and sex) from northern Ethiopia and a population of known age and sex cross‐bred red junglefowl (Gallus gallus L., 1758), curated at the Natural History Museum at Tring (UK). Considered together, these datasets provide insight into African poultry development and offer the first metrical baselines of chickens with known history in the region. Thus, this study has the potential to underpin future studies of domestic fowl morphology in Africa.