Will humans wipe out humanity?

THE importance of science in society has no greater spokesperson than Lord Martin Rees. From his perch at Cambridge--and a centre he formed on studying existential risks--he has served as both a promoter, populariser and the moral conscience of scientific endeavour far beyond his academic field of astrophysics. In "Our Final Century" in 2003 (retitled more breathlessly "Our Final Hour" in the American edition) he presented a range of global challenges, from bioterrorism to nuclear weapons. He put the risk of human extinction by 2100 from our technologies at around 50%. His latest book, "On the Future", is more sanguine.