“How often do you feel close to people?” As many as 30 percent of Americans don’t feel close to people at a given time…

Natural selection favored people who needed people. Humans are vastly more social than most other mammals, even most primates, and to develop what neuroscientists call our social brain, we had to be good at cooperating. To raise our children, with their slow-maturing cerebral cortexes, we needed help from the tribe. To stoke the fires that cooked the meat that gave us the protein that sustained our calorically greedy gray matter, we had to organize night watches. But compared with our predators, we were small and weak. They came after us with swift strides. We ran in a comparative waddle.

So what would happen if one of us wandered off from her little band, or got kicked out of it because she’d slacked off or been caught stealing? She’d find herself alone on the savanna, a fine treat for a bunch of lions. She’d be exposed to attacks from marauders. If her nervous system went into overdrive at perceiving her isolation, well, that would have just sent her scurrying home. Cacioppo thinks we’re hardwired to find life unpleasant outside the safety of trusted friends and family, just as we’re pre-programmed to find certain foods disgusting.

via The Lethality of Loneliness