WHY WE KEEP GETTING FASTER Widely recognized world records for events ranging from the mile to the marathon existed by the late nineteenth century (although the marathon distance was not formalized at 26 miles, 385 yards until well into the twentieth century). In 1886, the mile world record was 4:12.75. In 1908, the marathon world record was 2:55:18. The world records at these distances and every distance in between have dropped dramatically over the past century. At the time of this writing, the men’s mile world record stood at 3:43.13 and the men’s marathon world record at 2:03:59. The rate at which world records are broken has slackened in recent decades compared to when the events were new, but they continue to fall, as do major national records and age-group records. Experts have forecasted the imminent end of running record progressions for generations, and while we are certainly closer to the end now than ever before, it is amazing how long we have been able to sustain the march. Explaining this phenomenon has become a fun parlor game for running fanatics with a scientific mind-set. Many have pointed to a growing talent pool as part of the explanation. For example, until the 1960s East Africans did not compete internationally in running. When they began doing so, the rate of record-breaking increased. Now that people in most parts of the world have the opportunity to run, it is the growth of the world’s population that increases the talent pool. Everyone knows that a runner must first win the genetic lottery to have any hope of breaking records later through proper training and long-term development. Researchers have already isolated a number of genes that support endurance performance, each of which exists in only a minority of the population. For example, a gene variant called R577X, which exists in just 18 percent of the population, alters metabolism in fast-twitch muscle fibers in a way that enhances their endurance capacity. As of 2007, scientists had found 23 such genetic variants that tend to favor endurance performance. The odds of any single person having all of them are 0.0005 percent, according to Alun Williams of Manchester Metropolitan University in England, who published a paper on this topic.1 And it is widely agreed that other performance genes are yet to be discovered, bringing the chances of the perfect runner being born even lower. However, Williams noted in his paper, with population turnover, the chance of such genetically gifted individuals existing increases. In other words, as the world population grows, genetic lottery winners with increasing numbers of endurance performance genes are born. Consequently, Williams concluded, with population turnover world and Olympic records should improve even without further enhancement of environmental factors, such as better training and nutrition.