In 1900, off the coast of South Africa, a British torpedo boat attempted a solemn burial at sea for a 37-year-old Englishwoman. The coffin bobbed straight back to the surface, forcing the crew to fish it out and strap an anchor to it before the ocean would accept her. It is the perfect metaphor for Mary Kingsley, who spent 29 years confined to a London house as her invalid mother's caretaker, educated by nothing but her explorer father's library, until both parents died within months of each other in 1892 and an inheritance handed her total freedom. She spent it on a ticket to uncharted West Africa.

Her methodology was as radical as the trip itself: she lived with local populations instead of in fortified settlements, traded practical nursing care for wilderness survival training, learned indigenous fish traps well enough to discover specie ...