Since I've moved to Las Vegas, my social and romantic situation has changed. Being the new kid means that I'm still working on creating a social millieu. I'm also not currently in a relationship. Having gone through marriage (rather like having gone through "the war"), long term relationships, graduate school with a cohort, raising my daughter, and living with my family of origin, this is the first time I've really been alone. Its a strange feeling.
On the one hand: I don't need to check in with a partner or a parent or get a babysitter if I decide I'd like to do something. I can play torch songs as loud and and frequently as I please. My wine making projects can hijack the spare bedroom and my wool can sit anywhere it wants. If I don't want to clean the kitchen/livingroom/bedroom, no one complains. I can make decisions on money, vacations, and everything else without consulting anyone. That's nice. It's an enviable amount of freedom.
On the other hand: It's sometimes lonely.
So, why does loneliness bother us, meaning me? I think it's because humans are mammals, specifically primates. All animals have social constructs. This is for the protection of the individual as well as the health of the herd or troupe or flock. The worst thing that can happen to an animal is to be separated from the group. It leaves them in a vulnerable position, open to starvation, illness and predation. In primate groups and horse herds, if a member misbehaves they are pushed to the fringes of the circle until they show that they are sorry for their behavior.
In Celtic society, there was no corporal punishment. Instead, offenders were exiled, usually to Scotland. Solo travel was greatly discouraged in most countries until the 19th century because of the dangers lurking behind every tree. These were very real dangers that included banditry, animal attack and sexual assault. Women who had been widowed and lived alone were targeted by their neighbors as witches. Individuals in abusive relationships will stay even to the point of death in order not to be alone. It has always been safer to live in the herd or to be coupled than to be alone.
The benefits of the herd are numerous. Sharing the food, the labor, the childrearing. We need laughter, music and storytelling. We help each other with building shelter, protect each other in times of danger and share our individual gifts to make life better and richer.
So, aside from the reproductive imperatives of coupling up with a mate to make more of ourselves we are also hardwired to need to be part of a group of some kind. The medical evidence shows that people with active social lives are healthier and live longer. Married men are healthier and live longer (married women not as much). If we could all find ways to keep these social needs met in a supportive way that doesn't lead to destructive behavior, it would lead to healthier, happier members and a happier, healthier world.