PERSONAL HEALTH Evolution is an excellent teacher when it comes to figuring out what and how much people should eat. For example, primates (including those with two legs and big brains) evolved on foods rich in potassium and very low in sodium. Early humans evolved to conserve sodium, which was hard to obtain, and to excrete excess potassium, abundant in many fruits and vegetables. But Western-style diets these days are the reverse of what those early humans consumed, rich in processed foods, loaded with sodium and relatively poor in potassium. Consequently, according to a report released this year by the...