Â鶹Éç

Available for over a year

Why do humans have five fingers on each hand? The answer is: pure chance. Dr Lauren Sallan explains how our ancestors had seven or eight digits but then a mass extinction event wiped out most of life on Earth, except for small pockets of survivors. All the seven- and eight-digited animals never appeared again, but when our tetrapod ancestors emerged 15 million years later, they had five fingers.