No relationship we enter into ever has quite the intensity of romance. It is weird and wonderful thing that has haunted poets, philosophers, kings and queens and the humblest citizens in every age. As thought from nowhere the whole body changes, the mind grows besotted and no longer the master of its on destiny. The signs are unmistakable: a dreaminess of demeanour, a constant desire to be with the beloved, a willingness to oblige their every whim, and a near complete indifference to everyone and everything else. To be sure, not everyone suffers the full rigours of the condition, but it is general enough and (occasional denials notwithstanding) sufficiently cross-cultural to count among the handful of human universals in addition to laughter and tears. Peculiar of they are, romantic relationships share with friendships the same processes of evaluation and assessment, the same dependence of trust, the same fragility when exposed to being let down, the same risk of abandonment when somebody better comes along.

—Robin Dunbar, Friends, Little Brown, 2021