Could human engineering stabilise the Earth's climate and chemistry in the long term? Or will life eventually be extinguished by the expanding sun? Could humans seed life on other planets? And what will be our ultimate legacy in the Earth's geological record?

Tim Lenton of Exeter University explains why the Gaia hypothesis is the key to understanding the future of life on Earth. But what about life beyond Earth? Justin Rowlatt speaks to astronomer Lisa Kaltenegger - a hunter and explorer of planets outside our solar system - and to the science fiction author David Brin. Plus paleobiologist Jan Zalasiewicz describes what might remain of human civilisation in the geological record 100 million years hence.

Producer: Laurence Knight

(Photo: Skull fossil artwork from the Modern Fossils collection by Christopher Locke. Credit: Christopher Locke/Heartless Machine) Show less