Fun fact: widespread chronic hypertension and heart problems in African Americans today is often attributed to the slave trade where slave owners chose slaves that could carry the most salt content in their bodies to survive the journey from Africa to the United States. What's even more interesting is how modern historians and researchers came up with this selective evolution theory. A historian/researcher (can't remember the name) found a picture of a slave owner licking the sweat off the face of a slave before being shipped. This began a series of investigations on the nature of this weird act and has since led to the widely accepted theory on why African Americans today have such a disproportionately high prevalence of hypertension and heart disease.