Changes in human skull morphology across the agricultural transition are consistent with softer diets in preindustrial farming groups
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Edited by Clark Spencer Larsen, The Ohio State University, Columbus, OH, and approved June 19, 2017 (received for review February 14, 2017)

Significance
Agriculture changed not only human culture and lifeways, but human biology as well. Previous studies indicate that softer agricultural diets may have resulted in a less robust craniofacial morphology in early farmers. However, obtaining reliable estimates of worldwide subsistence effects has proved challenging. Here, we quantify changes in human skull shape and form across the agricultural transition at a global scale. Although modest, the effects are often reliably directional and most pronounced in craniofacial features that are directly involved in mastication.
Abstract
Agricultural foods and technologies are thought to have eased the mechanical demands of diet—how often or how hard one had to chew—in human populations worldwide. Some evidence suggests correspondingly worldwide changes in skull shape and form across the agricultural transition, although these changes have proved difficult to characterize at a global scale. Here, adapting a quantitative genetics mixed model for complex phenotypes, we quantify the influence of diet on global human skull shape and form. We detect modest directional differences between foragers and farmers. The effects are consistent with softer diets in preindustrial farming groups and are most pronounced and reliably directional when the farming class is limited to dairying populations. Diet effect magnitudes are relatively small, affirming the primary role of neutral evolutionary processes—genetic drift, mutation, and gene flow structured by population history and migrations—in shaping diversity in the human skull. The results also bring an additional perspective to the paradox of why Homo sapiens, particularly agriculturalists, appear to be relatively well suited to efficient (high-leverage) chewing.
Footnotes
- ↵1To whom correspondence should be addressed. Email: david.katz{at}ucalgary.ca.
Author contributions: D.C.K., M.N.G., and T.D.W. designed research; D.C.K. performed research; D.C.K., M.N.G., and T.D.W. analyzed data; and D.C.K., M.N.G., and T.D.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
See Commentary on page 8917.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1702586114/-/DCSupplemental.
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