Jill Heinerth is the world's top underwater cave explorer. More people have walked on the moon than have ventured to some of the places she has dived. Originally from Canada, and now living in Florida in the US, Jill has broken records mapping whole water courses underground, and once had a narrow escape from cave-diving in an Antarctic iceberg. She takes photographs and video whilst underground, and says that she would never attempt a dangerous dive just for the thrill of it - there has to be a new discovery to pursue.

Elen Feuerriegel is a PhD student from Australia who was catapulted into one of the most exciting scientific discoveries of our time, when her caving experience and slim build led to her joining the Rising Star Expedition. This all-women team excavated over a thousand fossils from a deep cave system in South Africa, which at its narrowest point measures just 18 cm. It was announced in September 2015 that these bones were from a previously unknown species of human ancestor, Homo Naledi.

(Photo: (L) Jill Heinerth in diving gear, Credit: Wes Skiles. (R) Elen Feuerriegel holding MH1)