According to super brains such as Stephen Hawking
Daily Mail 
September 13, 2013
They are an improbable group of superheroes. But some of Britain’s greatest minds have got together to focus their powers on saving humanity from itself.
Once the threats have been identified, the group intend to devise ways of ‘ensuring our own species has a long-term future’.
Although nuclear annihilation and a giant asteroid obliterating the planet remain distinct, if unlikely possibilities, Lord Rees now believes ‘the main threats to sustained human existence now come from people, not from nature.’
Other scenarios being considered by the 27-strong group, which also involves academics from Oxford, Imperial, Harvard and Berkeley, include extreme weather events, fast spreading pandemics, and war or sabotage resulting in a shortage of food and resources.
Speaking last night at the British Science Festival at the University of Newcastle, Lord Rees said: ‘In future decades, events with low probability but catastrophic consequences may loom high on the political agenda.
‘That’s why some of us in Cambridge – both natural and social scientists – plan, with colleagues at Oxford and elsewhere, to inaugurate a research programme to compile a more complete register of these existential risks, and to assess how to enhance resilience against the more credible ones.’
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