Why the human race keeps getting faster.

Why the human race keeps getting faster.

By Andrew Berry

(2,168 words; posted Thursday, July 4; to be composted Thursday, July 11)

On May 6, 1954, at Oxford University's Iffley Road track, Roger Bannister became, by just half a second, the first man to run a mile in less than four minutes. The Holy Grail of middle-distance running was his. Forty-two years later, however, that achievement seems less significant. Four-minute miles are commonplace; the current record, held by Algerian Noureddine Morceli, is 3:44 , more than 5 percent faster than Bannister's speed. What Iffley Road witnessed was just another step along the road to an ever quicker mile, part of the inexorable improvement of athletic performance that we usually take for granted, particularly when the Olympics roll around. If you stop to think about it, though, such constant progress is remarkable. After all, as biomechanical machines with a standard set of parts, humans should be subject to the same limitations we see in, say, automobiles. How come they aren't?

A lot of entrepreneurs and technophiles would like us to think that the answer has to do with discoveries in the world of sports technology. A new Nike shoe is trumpeted as something that will shave at least one-thousandth of a second off your 100-meter time. Trainers measure the rate of buildup of lactic acid in your muscles, then claim that their programs will control it. Nutritionists fine-tune athletes' diets. Even the old sexual-abstinence-before-the-race dogma is being re-evaluated under the all-seeing eye of science. But I consider all this little more than tinkering. Sports records would continue to tumble even if training methods or athletic clothing or sexual practices were exactly the same today as they were in 1896, when the first modern Olympics took place. These minor miracles are the product neither of technology nor of training but of demographic patterns that affect us all.

Over the past century, the human race has been affected by a slew of what demographers call "secular" trends. (In this context, "secular" does not refer to a trend's lack of spirituality but to its longevity: Secular trends are long-term modifications, not just brief fluctuations.) One such trend is an increase in average size. You have to stoop to get through the doorways of a Tudor cottage in England because its inhabitants were smaller than you are, not because they had a penchant for crouching. Another trend is in life expectancy. People are living longer. Life expectancy in Africa increased over the past 20 years from 46 to 53 years. Over the same period in Europe, where things were already pretty comfortable to begin with, life expectancy increased from 71 to 75 years. The global average was an increase from 58 to 65 years.

Probably the most striking change, though, is how much more quickly children are maturing. A 12-year-old child in 1990 who was in what the World Health Organization calls "average economic circumstances" was about 9 inches taller than his or her 1900 counterpart. This is not solely the product of the first trend--the increase in average size--but also due to the fact that children develop faster. Girls menstruate earlier than they used to. The age of menarche (the onset of menstruation) has decreased by three or four months per decade in average sections of Western European populations for the past 150 years. There is a good chance that our 1990 12-year-old already had started to menstruate. Her 1900 counterpart would still have had three years to wait.

What do such trends have to do with athletic performance? Well, if we're living longer and growing up faster, that must mean we're producing bigger, better bodies. Better bodies imply faster miles. We run faster and faster for the same reason it is now common for 11-year-old girls to menstruate. But why are these things happening?

Demographers have offered a variety of explanations, but the main one is that our diet is improving. A 12-year-old ate better in 1990 than she would have in the Victorian era. This conclusion is supported by studies of the social elite: Because its members were well-nourished even in the early years of this century, this group has experienced relatively little change, over the past 100 years, in the age girls first menstruate. Another explanation is that health care is getting better. In 1991, according to the WHO, more than 75 percent of all 1-year-olds worldwide were immunized against a range of common diseases. Smallpox, that scourge of previous generations, now is effectively extinct. Probably the best measure of how much healthier we are is the rate of infant mortality, which measures both the health of the mother (a sickly mother is more likely to produce a sickly baby) and the health of the baby. In the past 20 years, infant mortality around the world has dropped from 92 deaths per 1000 live births to just 62. A lot of this can be chalked up to primary-heath-care programs in the developing world--the African average, for instance, has dropped from 135 deaths per 1000 births to 95. But there are also significant improvements in the developed world, with infant deaths dropping in Europe over the same 20-year period from 24 per 1000 live births to just 10.

Better health care affects athletic ability directly. This is true in the trivial case in which, say, antibiotics cure a runner's fever before the big race, but it may also be true in a more significant way. Diseases contracted in early infancy can have a lifetime impact on health--not necessarily a big one, but an impact nevertheless. Previous generations bore scars from all sorts of non-life-threatening diseases, the stuff everyone picked up as a baby. Nowadays, though, more and more people grow up with no history of disease. Since top athletes inevitably are drawn from the healthiest sector of the population, a generally superior system of health care means a bigger pool of people to draw from. You are much more likely to find someone who can run a mile in 3:30 in a sample of several million superbly healthy people than you are in a sample of 10,000.