Hypertension is the silent killer driving the global public health burden of cardiovascular and renal disease. Blood pressure is strongly influenced by the distribution of sodium chloride (salt) between fluid compartments of the body and within tissues. Most societies consume 10 times more salt than is required by physiological need. This high salt intake is strongly linked to hypertension. The World Health Organisation targets a ∼30% reduction in salt intake in order to arrest the high levels of death due to cardiovascular disease. But how does an habitually high salt diet cause blood pressure to rise? This lecture presents the concept that hypertension is a modern disease caused by our changing world. It first examines how our ancestral DNA provided an evolutionary selection advantage during early mammalian development but is now maladaptive. The lecture discusses the control of body salt by multiple organ systems in the body and ends with new evidence that our brain exerts a significant effect on blood pressure by controlling our hunger for salt.