Wherever we look, population is the driver of the most toxic issues on the political agenda. But the population bomb is being defused. Half the world's women are having two children or fewer. Within a generation, the world's population will be falling. And we will all be getting very old. So should we welcome the return to centre stage of the tribal elders? Or is humanity facing a fate worse than environmental apocalypse? Brilliant, heretical and accessible to all, Fred Pearce takes on the matter that is fundamental to who we are and how we live, confronting our demographic demons.