Asked by: David, Fulford-Brown, by email
Because wanting to avoid the situations that cause it would have helped our ancestors survive. We are a social species that naturally lives together in close-knit groups. So those of our ancestors who felt awful when they were rejected by friends or family would have tried to avoid such events. They would have made better group members and been more likely to survive and pass on the capacity for emotional pain to their offspring. When things do go wrong, the pain suffered can act as a reminder – don’t get into a relationship like that again! Or don’t treat people the way you did before. Perhaps unsurprisingly the underlying mechanisms are closely related to those for physical pain. For example, social rejection and grief have effects visible in the brain’s anterior cingulate cortex, which is also involved in physical pain, and both types of pain affect the heart and hormonal systems. This is why we say “it hurts” when we feel rejected or unloved.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.