Statistically at least, a boy born in 1850 could anticipate living for 38.3 years, a girl for 40.5 years - a life expectancy not much altered in thousands of years. A boy born in 2085 will anticipate living - according to the U.S. Social Security Administration, which apparently needs to know these things 75 years in advance - for perhaps 93.8 years, a girl for 96.1 years. In other words, the grandchildren of boys and girls born this year will routinely anticipate living long enough to know their own great-great-grandchildren.
The Social Security analysts who crunch actuarial numbers don't make predictions. They calculate probabilities. They concede that life expectancy for U.S. males born 75 years from now could be as low as 81.3 years, a mere 5.7 years longer than for male babies born in 2010, as low as 84.7 years for females, a mere 3.9 years longer than for female babies born in 2010. But the probability of the larger increase is as great as the probability of the smaller increase. And although humble in comparison with best-scenario advances in life expectancy, the smaller gains still represent stunning change.
Assuming that advances in longevity continue at even a modest rate - extending life expectancy, say, another month every couple of years - the best-scenario average lifespan will be taken for granted long before it actually happens. By 2085, centenarians will number in the hundreds of thousands in the U.S., in the tens of thousands in Canada. (The U.S. now has 100,000 centenarians, Canada 5,000.) The longevity analysts already calculate life expectancy rates for 119-year-olds. They will need to extend this "last year of life" calculation to an improbable 135 years to maintain the same relative statistical perspective.
Canadians live longer than Americans. Assuming that this cross-border gap holds for the next 75 years, a Canadian boy born in 2085 should be able to anticipate living - again, best-case scenario - for 96.5 years, a Canadian girl for 98.2 years. After more than 200 years of increases in lifespan, though, the gender gap will remain, whittled down from 2.2 years in 1850 to 1.7 years in 2085.
The average global life expectancy blends the very highest rates in the world with the very lowest. Japanese women (current life expectancy: 86.1 years) now live longer than anyone else. They will be the first to anticipate a 100-year lifespan as a national average. The breakthrough could occur as early as 2028. Around the world, with the exception of African countries cursed with 1850s lifespans, any person who subsequently dies at 70 - "threescore years and ten," in the King James tradition - will have died young. This, too, is epochal change for a humanity accustomed to lives that were historically nasty, brutish and short.
How long can life expectancy keep increasing? The best answer is a calculation of probability. U.S. average death rates have fallen by 1.07 per cent a year for the past 100 years. They have kept falling, in recent years, at a quickening pace - "constantly," the trustees of Social Security say, "exceeding expectations." There is no reason to think that death rates won't keep falling.
In Psalm 90, a melancholy poet dismisses long life itself as a curse. "The length of our days is 70 years - or 80, if we have the strength," one translation runs. "Yet their span is but trouble and sorrow, for they quickly pass and we fly away." Most translations use the words "labour" or "toil" instead of "trouble" - reflecting the pervasive mindset, then and now, that equates work with pain and suffering. The psalmist forgets that the only alternative to a long life is a short one. And, everyday lamentations aside, most people find meaning and solace in work.
We are often informed that the "greying" of the advanced countries means wrenching social and economic change - and an acute shortage of workers. ("What on earth will we do with all the elders?" writer Judy Steed once asked. "Cut them loose on melting ice floes?") But people will defy mortality not only by living longer but by living, in Olympian terminology, faster, higher and stronger.
Technology will help. In BlackBerry Planet , the compelling story of the "little device that took the world by storm," Ottawa historian and seer Alastair Sweeny anticipates - among other fascinating things - "TeleBrain" implants that extend indefinitely the memory functions of healthy brains. Most elderly people will keep working. Freedom 75 will replace Freedom 55. Few people will want to spend the last 40 years of their lives playing golf.