30 articles
Anesthesiologists have long joked that redheads need more anesthesia. Studies back it up, at least partly. What the research found about redheads, pain and anesthetics, and what it means at the dentist.
Natural red hair is the rarest hair color in the world. The gene behind it, where redheads are most common, how two brown-haired parents can have a redheaded child, and the myths…
Eight common blood types, ranked by how often they show up in the U.S. population, plus who can give to whom and why O-negative donors are always in demand.
Only a few dozen people on Earth have been reported to have Rh-null blood, nicknamed golden blood. What it is, why it's so valuable, the health challenges, and how it was discovered.
One blue eye and one brown, or a splash of a second color in one iris. The three types of heterochromia, what causes them, how rare it is, and why it's common…
About 1 in 10 people is left-handed. What the largest study ever found, why the number changes by country and era, and the myths and facts about lefties.
