It is the percentage of humans who, across all cultures, time periods studied, and corners of the globe, preferentially use their right hand. In more than 95% of right‑handed people, language resides in the left hemisphere. In the human brain, hand and speech travel together. And from the way the oldest flakes are knapped, archaeologists can infer that most of those hominins struck with the right hand. A non‑dominant hand, a dominant hand, and two million years of questions that still lack a definitive answer.