Natural selection being the thrifty thing it is, the biology behind those feelings and thoughts was a straightforward extension of the biology embodying those original values. Brain-scan studies have shown that the same parts of the brain that mediate physical pain also mediate the pain of social rejection. Which helps explain why opiates and other painkillers can take the sting out of social setbacks. Even extended doses of Tylenol, one study showed, can dull the pain of social rejection.
