It has been suggested that certain physical cues can be used to predict mate quality, and that sensitivity to these cues would therefore be adaptive. It follows that in environments where the optimal values for these features differ, attractiveness preferences should also be different. In this study, we show that there are striking differences in attractiveness preferences for female bodies between Thai observers in affluent, industrialised environments as compared to Thai observers in resource-poor, hill tribes. These differences can be explained by different local optima for survival and reproduction in the two environments. In industrialised societies, a high body mass is correlated with low health and low fertility, and the converse is true in rural Thailand. These results suggest that humans have mechanisms for acquiring norms of attractiveness that are highly plastic, and which allow them to adapt to different ecological conditions through learning.