The four tastes humans are most familiar with are sweet, sour, salty and bitter. In 1908 a Japanese chemistry professor discovered a fifth - savory. Now a behavioral geneticist has discovered that mice have receptors that detect calcium. Because mice and humans have many genes in common, it’s likely calcium is a sixth taste. Supposedly calcium is what gives high-calcium vegetables - like kale and collard greens - their bitter flavor. The reason we don’t detect calcium when we eat dairy products is it binds with fats and proteins. Further research, however, will confirm if human tongues actually have these “miceroscopic” receptors.