Human societies, at all times and places, have organised themselves around the will to live with others, not alone. But not any more. During the past half-century, our species has embarked on a remarkable social experiment. For the first time in human history, great numbers of people – at all ages, in all places, of every political persuasion – have begun settling down as singletons. Until the second half of the last century, most of us married young and parted only at death. If death came early, we remarried quickly; if late, we moved in with family, or they with us. Now we marry later. We divorce, and stay single for years or decades. We survive our spouses, and do everything we can to avoid moving in with others – including our children. We cycle in and out of different living arrangements: alone, together, together, alone.
Numbers never tell the whole story, but in this case the statistics are startling. According to the market research firm Euromonitor International, the number of people living alone globally is skyrocketing, rising from about 153 million in 1996 to 277 million in 2011 – an increase of around 80% in 15 years. In the UK, 34% of households have one person living in them and in the US it's 27%.