If human culture emerges from the modal personality of a population, can global variation in parasitism that affects personality lead to cultural diversity among nations? The answer could help explain why people seem to vary so much from one land to another. Thomas et al. (2005) review how parasites manipulate behaviour, inc v t d g m r s r b r t p i r Other parasites are much more common in human populations. Some may have the ability to enact subtle, but long-term, changes in behaviour – to the extent of changing personality. The most notable example is Toxoplasma gondii. This parasite is primarily of concern because it can cause pathology under some