Skull and limb morphology differentially track population history and environmental factors in the transition to agriculture in Europe

Abstract

The Neolithic transition in Europe was a complex mosaic spatio-temporal process, involving both demic diffusion from the Near East and the cultural adoption of farming practices by indigenous hunter-gatherers. Previous analyses of Mesolithic hunter-gatherers and Early Neolithic farmers suggest that cranial shape variation preserves the population history signature of the Neolithic transition. However, the extent to which these same demographic processes are discernible in the postcranium is poorly understood. Here, for the first time, crania and postcranial elements from the same 11 prehistoric populations are analysed together in an internally consistent theoretical and methodological framework. Results show that while cranial shape reflects the population history differences between Mesolithic and Neolithic lineages, relative limb dimensions exhibit significant congruence with environmental variables such as latitude and temperature, even after controlling for geography and time. Also, overall limb size is found to be consistently larger in hunter-gatherers than farmers, suggesting a reduction in size related to factors other than thermoregulatory adaptation. Therefore, our results suggest that relative limb dimensions are not tracking the same demographic population history as the cranium, and point to the strong influence of climatic, dietary and behavioural factors in determining limb morphology, irrespective of underlying neutral demographic processes.

Bone functional adaptation does not erase neutral evolutionary information

“…Some of our results conflict with those previously reported by Betti et al (), who found that long bone variation was more indicative of climate than of population structure. Similar results were reported by von Cramon‐Taubadel, Stock, & Pinhasi (), who found long bones (grouped by limb) were not useful to discern neutral genetic information, being more influenced by environmental variables like temperature and latitude. The differences between our results and theirs are likely due to methods and sampling.…”

“…There are also a number of other minor differences, including standardization method. Both Betti et al () and von Cramon‐Taubadel et al () used geometric mean while we controlled for mass effects and Z ‐score transformed our data to control for size. Another difference was our emphasis on diaphyseal properties.…”

Gradual decline in mobility with the adoption of food production in Europe

“…However, unlike craniometric variables (51), limb bone dimensions do not appear to track population history in Europe (52). Recent work also indicates that the general genetic pool from which all Holocene Europeans were derived is ancient, extending back before the earliest specimens in our sample (53) and implying overall continuity despite periodic migrational events.…”

Sexual Dimorphism of the Human Tibia through Time: Insights into Shape Variation Using a Surface-Based Approach

“…Adult long bone morphology is a complex product of genetic and environmental interactions [64,65] but major evolutionary features may be principally genetic and the remaining skeletal features are more or less environmentally modifiable [65]. Thus we assume that most of the observed temporal variation is derived from epigenetic influences such as climatic, dietary and behavioural factors [66]. …”