Nausea and vomiting during pregnancy (commonly referred to as morning sickness) affects approximately two-thirds of human women, with debilitatingly-severe effects in up to 3% of women. Despite how common morning sickness is, there is an ongoing debate about why morning sickness has evolved. One hypothesis–the prophylaxis hypothesis–suggests that nausea during early pregnancy leads women to avoid eating products that could disrupt organ development and, in support of this hypothesis, morning sickness is more common in societies that more commonly eat toxic foods. Additionally, a claim has been made that morning sickness is unique to humans, despite evidence that our closest relatives, the primates, also suffer from a lack of appetite and dietary changes in early pregnancy. This project will test the prophylactic hypothesis in a desert-dwelling primate with a high diet of toxic foods: the chacma baboon. There will be a large fieldwork component comparing diets of baboons at different stages of pregnancy and developing methods to remotely detect nausea using thermal imaging in the wild. Baboons are an ideal species for this because they are numerous; reproductive events, including ovulation and pregnancy, are obvious; and visibility is excellent, allowing detailed behavioural observations to be made in situ.