Mother Nature doesn't give a crap about our moral imperatives. She doesn’t care if people we judge to be worthy (the poor, the persecuted, the people of colour, the handicapped, the fashionably oppressed) should be lifted on to our lifeboat, only if it is overloaded. And whether the passengers live together without class barriers or in feudal subjugation is of no concern to nature either. The laws of physics trump the laws of any Holy Text, ethical system or left-wing manifesto. If we want to survive, we will have to play by nature's rules, not ours.