Living alone doesn't necessarily make you lonely. But it certainly doesn't help. Individuals have varying levels of need for connection with others. 1 But when your needs and your situation don't match up, you may feel a little pain in your heart to go along with that unpleasant impression that you're floating alone on a raft in the middle of the ocean. And that's a good thing, says University of Chicago neuroscientist John Cacioppo, who recently co-wrote a book called "Loneliness." In the same way that physical pain helps protect you from physical danger, says Cacioppo, social pain evolved to help keep individuals from the dangers of social isolation. 2 Just as the discomfort of skin tells your brain to pull your hand away from boiling water, loneliness developed as a stimulus to get humans to pay more attention to the people around them, thus reaching out and touching someone. 3 Here's how it works: The empty feeling of loneliness is an alarm signal embedded in our genes that devotes itself to telling us when to reach out to others and causes a chain of physiological reactions that we know as the fight-or-flight response. Fight-or-flight creates increased resistance in our cardiovascular system and floods our bodies with hormones that pump us up. Long ago, these hormones helped our ancestors run from danger or fight it off. Today, however, in the absence of imminent attack by a tiger, these chemicals can be a corrosive force to the body. In contemporary society, the fight-or-flight response may not be over quickly. We can suffer the same feelings of loneliness week after week, year after year, wearing down the body's metabolism. All of this means we need to take the problem of lagging civic engagement and growing social isolation out of the realm of the social sciences and put it in the physical sciences. We have to stop looking at declining civic participation as a primarily political problem that is solvable through increased activism. 4 Although activism may increase participation, which in turn translates into less social isolation, it does not get to the deeper problem of the quality of connections we form with the people who surround us on a day-to-day basis. As Cacioppo puts it, 5 "If civic engagement is to contribute substantially to relieving loneliness, then it cannot be something merely similar to networking at a trade show." Nature gave us a warning system that reminds us of the dangers of being isolated from our fellow man. Millions of alarm bells are ringing.