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.
The pool of potential athletes has expanded in other ways, too. First, the population has exploded. Second, we are coming ever closer to a worldwide middle class, the class from which athletes typically are drawn. Whether, in an age of multinational capitalism, we may talk reasonably about a post-colonial era is way beyond the scope of this article. The fact remains, however, that the developing world is doing just that--developing. Even Mozambique, which ranks at, or near, the bottom of national per capita gross national product tables, has shown an increase of some 20 percent in adult literacy rates over the past 20 years. Literacy rates are merely an index of education, which itself is another way of talking about a global move away from a hand-to-mouth lifestyle.
The decline of empire has its Olympic corollaries. Britain won, on average, 17 gold medals per Olympics in the five official games held in its imperial heyday before World War I. That average has dropped to only five medals per Olympics in the 17 held since. This is not a reflection of declining athletic standards in Britain, however; it's a function of how much more competitive other nations have become. The Olympics originally were the preserve of the socioeconomic elite of the socioeconomic elite among nations. Consider this: Only 13 nations participated in 1896, but there were 172 in 1992. Black Africans didn't take part until the third modern games, held in St. Louis in 1908. Even this was accidental: Lentauw and Yamasami, Zulu tribesmen, entered the marathon because they happened to be in St. Louis as part of an exhibit about the Boer war. Lentauw finished ninth despite being chased into a cornfield by dogs.
Since all these are changes in how we live, not anything innate, we have to conclude that what we are describing here are effects of environment, not genes. Let us assume that our 1900 and 1990 12-year-olds are identical twins magically born 90 years apart. The 1990 girl still will grow up faster, end up bigger, menstruate earlier, and live longer than the 1900 girl. Perhaps way, way back in human history, when our forebears were still fleeing saber-toothed tigers, natural selection for athletic prowess came into play. But all that ended long ago. Indeed, the laws of natural selection probably work against athletes these days: Given the rigors of training schedules, it is possible that today's top athletes have fewer children than average.
Just because nurture has a more significant effect on athletic performance doesn't mean that nature lies dormant, though. Genetic variation exists for just about any trait you choose to study, and the ability to run quickly would be no exception. To take a trivial case, we know that the inheritance of extra fingers or toes is determined genetically. It is quite possible that the possession of an extra toe would hinder an aspiring miler--their genes have affected their athletic performance. One genetic factor that may be influencing performance trends is what is known as "hybrid vigor." Cattle breeders have known about this for a long time: Take two inbred lines of cattle, cross them, and what you have is "better" (say, larger) than any single individual in either of the two parental lines. This does not require natural selection; it is the accidental byproduct of combining two previously isolated stocks. There are a number of theories to account for this at the genetic level, but it has proved difficult to discriminate among them. It is possible that modern humans exhibit some form of hybrid vigor simply because migration and admixture of populations are now occurring at unprecedented rates. Perhaps, just perhaps, such hybridization is being translated into enhanced performance.
That doesn't mean, however, that genetic differences in athletic ability can be correlated automatically with race. That is a claim that is impossible to test, because you cannot control, in an experimental sense, environmental differences among the study groups. Sure, you will find more Africans or descendants of Africans standing on the podiums at the end of Olympic track events. And you will find far fewer Asians on those same podiums. But can you, therefore, conclude that Africans have better genes for running than Asians do? No. Environmental differences between the two groups could account for differing levels of athletic success. It is scarcely surprising that Ethiopian or Kenyan distance runners do better than everyone else, since they are in the habit of running immense distances to and from primary school, middle school, and high school. The training is what's crucial, not the blackness. The Chinese sports establishment also has carried out an enormous, and effective, experiment to help dispel the myth that race has a direct relation to athletic ability. Until recently, a quick glance at the medals table confirmed every stereotype people held about Asians and sports. Then the Chinese decided to produce record-breaking female distance runners (and swimmers), and, boy, did they ever. In 1992, China ranked fourth in the Olympic-medal haul.
You can bring a single generation up to speed through training, but the trends we're dealing with transcend individual generations. Which brings us to another question: Will there come a time when the human machine will hit some sort of natural limit and an Olympic Games pass without a single record tumbling? In principle, yes.
There are some barriers that simply cannot be broken. We will never run a mile at the same speed at which we now run 100 meters, for instance. The laws of oxygen exchange will not permit it. Race horses seem already to have hit that outer limit. For years, they were as good as human athletes at pushing back speed records, but then they simply stopped getting faster. Take the prestigious British Derby. From 1850 to 1930, winning times dropped from 2:55 to 2:39. But from 1986 to 1996, the average time has been--2:39. Unlike people, race horses are specifically bred and reared to run. Generations of careful genetic selection have ensured that today's race horse has every possible speed-enhancing characteristic. Training techniques, too, are tremendously sophisticated. But you can go only so far. You can only breed horses with ultralight thin bones to a certain point; the bones will break under stress if they get any lighter.
Human improvement, like race-horse improvement, must eventually bow to the basic constraints of biomechanics. The age of menarche cannot keep on falling forever. On the other hand, it is clear from the remarkable demographic changes of just the past 20 years that these long-term trends are with us still. They may be slowing down in some more developed societies, but they roar along in others. And these trends will continue to fuel the improvement in athletic performance. Several new records will be set in Atlanta. And in Sydney in 2000, and wherever the Olympics are held in 2044. We will continue running faster and jumping further for a good long while to come.