In 19 countries, from Singapore to Iceland, people have a life expectancy of about 80 years. Of all the people in human history who ever reached the age of 65, half are alive now. Meanwhile, women around the world have half as many children as their mothers. And if Japan is the model, their daughters may have half as many as they do.

Homo sapiens is ageing fast, and the implications of this may overwhelm all other factors shaping the species over the coming decades – with more wrinklies than pimplies, more walking frames than bike stabilisers, more slippers and pipes than bootees and buggies, and more grey power than student power. The longevity revolution affects every country, every community and almost every household. It promises to restructure the economy, reshape the family, redefine politics and even rearrange the geopolitical order over the coming century.