Sexually dimorphic traits are associated with subsistence strategy in African faces from the Sahel/Savannah belt

Previous research revealed that in some African populations, food-production strategies are associated with facial shape. Nomadic pastoralists living in the African Sahel/Savannah belt have a different facial morphology than their sedentary neighbours. We investigated whether the lifestyle associated with a subsistence pattern has an impact on sexual dimorphism in the facial structure. We employed several methods from geometric morphometrics and demonstrated such effect in four ethnically distinct populations that share the same geographic space. We show that the facial traits which correlate with a subsistence strategy are systematically associated with levels of facial sex-typicality. In particular, we found that faces with more pronounced pastoralist features have on average more masculine facial traits and that this effect is more pronounced in men than in women. In general, though, the magnitude of overall facial dimorphism does not differ between pastoralists and farmers. Pastoralists (in contrast to farmers) tend to have a more masculine facial morphology but facial differences between the sexes are in both groups the same.