It might surprise you to learn that human cells commit suicide. The process is called apoptosis. What happens is, cells in a dense cluster send each other survival signals, but those that get isolated from the group begin to self-destruct. As the biologist Martin Raff once wrote, the only thing keeping cells from killing themselves "is that other cells are constantly stimulating them to live."
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Turns out whole human beings may behave in a sadly similar way.
A new scientific working paper (spotted by Tim De Chant of Per Square Mile) contends that as population density decreases, the suicide rate among young people increases. This effect becomes particularly pronounced below 300 inhabitants per square kilometer—roughly the density of San Diego County. The research team, led by Chinese ecologist Lei Wang, wonders if social "shock" of moving from a dense city to a sparse countryside might have something to do with this unsettling link:
If young persons are more connected to their social environment, then the shock of moving out to a countryside environment will be more painful to them and, just as in the case of widowhood but with smaller magnitude, it will result in inflated suicide rates.
Let's backtrack a minute and consider density and mortality in general. The city has always seemed (at least to outsiders) like a hazardous place of crime and disease and countless interactions with complete and potentially dangerous strangers. But life at low densities has plenty of its own environmental perils: speedier roads and social disconnection, among them.