How about this for an argument to raise the retirement age: If you don't keep working, your community could die off. That's the threat posed by an intersection of biology and economics which could finally make some famous two-hundred-year-old predictions come true. As the world's population grows and successive generations consume more resources, can our economic productivity keep up?
More than two centuries ago, Thomas Malthus warned that food production couldn't keep up with population growth. Then the Industrial Revolution - and later the Green Revolution - proved him wrong. But you couldn't blame him for saying what he did in the late eighteenth century; as Sylvia Nasar's recent book, "Grand Pursuit", points out, humans' economic productivity was basically stagnant until the early 1800s. It was only as productivity shot up that we were able to support bigger communities and eventually to raise living standards as well.
This basic insight may be at the root of a counterintuitive twist of evolution. In recent years, scientists including Cynthia Kenyon and Ronald DePinho have
discovered "aging genes" that, when switched off or altered, allow organisms to live much longer. But the genes' presence in the first place is puzzling; why would animals evolve to live shorter lives?
The reason may be the lack of productivity gains in the animal kingdom. When animals live longer, the population of their community tends to grow; they have more time to procreate, and it takes them longer to die off. Yet this growth can make a community unwieldy - too many individuals to support using the same territory, resources, and command structure. In other words, there are decreasing returns to scale. If there weren't, herds of apes, flocks of birds, and other animal communities would be as populous as termites in a mound. So aging may be a natural form of population control, different and appropriate for each species.
It's not too hard to see how this would work in an evolutionary setting. What would happen, for example, if an animal was born with a mutation that slowed down aging? The animal's offspring might be expected to dominate its community, since they would live longer and procreate more themselves. If the animal's community grew too big as a result, however, it would collapse. Animals with the mutation would die out along with the others before they could spread their genes and dominate the entire species.
For humans, the story has been startlingly different. We are the first species to enjoy a huge increase in productivity like the one we've seen in the past two centuries. It's what has allowed our communities to grow, sometimes even generating increasing returns to scale. Our rising life expectancies are still a source of tension, though, because of constraints like pension programs and the the costs of health care for the elderly.
Falling birth rates may be helping with population control, but they also make paying those pensions and health care benefits even harder. Moreover, they tend to happen in countries that are getting wealthier, and parents want to invest a lot in just one or two children - fewer kids, but more consumption demanded by each of them.
As science helps us to live even longer, how well we live will depend greatly on whether our economic productivity can keep up. An easy way to raise productivity is to convert people from non-workers to workers. And one of the easiest ways to do that is to raise the retirement age. The only question is, will longer working lives - like longer working hours - mean fewer people being employed? We're almost certain to find out, as
Malthus rears his well-coiffed head again.