A 31,000-year-old skeleton, which was found two years ago in a cave in East Kalimantan on the island of Borneo in Southeast Asia, has revealed something truly fascinating. The individual was missing his lower left leg, and analysis of the stump showed that the bone healed after the leg was lost, several years before the individual died. Even more startling, it was a clean cut, meaning that this was no accident or animal attack — it was a deliberate amputation. And it must have been amputated by someone with deep knowledge of human anatomy, necessarily including blood vessels and nerves. After the surgery, the wound likely needed to be disinfected regularly, again indicating impressive knowledge...