The Sports Gene: Inside the Science of Extraordinary Athletic Performance

Chapter 11 explores a theory about the dominance of Jamaican sprinters that runs counter to the one put forth in Chapter 10. Scientist Erol Morrison connects sprinting ability with genetic variants that protect against malaria, specifically in western Africa, where malaria is (and was, at the time of the slave trade) rampant. Morrison’s theory relies on research from friend and fellow researcher Patrick Cooper, who “documented the fact that athletes with western African heritage become highly overrepresented in sprint and power sports almost immediately once they are allowed a fraction of their white counterparts’ access to sports” and set out to explain this phenomenon (176).

Two traits common to people with “recent sub-Saharan ancestry in west or central Africa" became relevant in Cooper’s research (177). One is the sickle-cell trait, which refers to “a mutation that causes round red blood cells to curl up in a sickle shape in the absence of oxygen, potentially impairing blood flow through the body during vigorous exercise” (177). Sickle-cell carriers are “genetically disadvantaged for long-distance sports” (177). Genetically low levels of hemoglobin, also common in people with recent sub-Saharan ancestry, also constitute a “disadvantage for endurance sports” (178). Cooper successfully argued “that sickle-cell trait and low hemoglobin are evolutionary adaptations to malaria” (180).

Cooper then searched for a “compensatory mechanism” in healthy athletes with these traits. He consulted research on a study of non-athlete students in western Africa that showed that “a higher proportion of muscle in the African students was composed of fast-twitch muscle fibers, and a lower proportion was slow-twitch muscle fibers compared with white students” (179). The conclusion was that western Africans “are, in terms of skeletal muscle characteristics, well endowed for sports of short duration” (179).

It is unknown and relatively untested, however, whether low hemoglobin was an evolutionary precursor to a higher proportion of fast-twitch fibers. Many scientists resist this type of research for fear that findings suggesting a certain ethnic group has a physical advantage over another would be socially problematic. Epstein cites Cooper in saying: “The concept that physical superiority could somehow be a symptom of intellectual inferiority only developed when physical superiority became associated with African Americans” in 1936 (185).

This chapter begins with a profile of KenSAP, the Kenya Scholar-Athlete Project, and its founder, John Manners. With KenSAP, Manners identifies academically high-scoring Kenyan high school students and has them run a timed trial of a 1500-meter race. He then selects the fastest students—many of them without prior training—and assists them in applying to American universities, soliciting admissions recommendations from prospective coaches.

KenSAP exists because Kenya is known for producing elite long-distance runners. Epstein focuses on the Kalenjin tribe, a population living in Kenya’s Rift Valley who “represent about 12 percent of Kenya’s population, but more than three quarters of the country’s top runners” (190). One theory Manners once put forth was one of artificial selection, in which ancestral members of the Kalenjin tribe participated in cattle-raiding, a practice that involved taking cattle from other tribes, traveling long distances, and reaping social rewards (like status and wives). Descendants of the best cattle-raiders, the theory holds, would carry genetic advantages in distance running.

Epstein lists anecdotes of Kalenjin runners who rose to prominence on the world stage of long-distance running despite backgrounds that wouldn’t suggest that path. Manners believes “the proportion of people who will become extremely fast middle-and long-distance runners extremely quickly upon training is significantly higher among the Kalenjin” than it is among other Kenyan tribes or other people around the world (192). However, Epstein suggests that “stumbling upon hidden distance running talent is not exclusive to Kenya” (194-95), and he argues that “the very systematizing of the process by which talent is stumbled upon makes it less like stumbling and more like tactical filtering” (195).

Scientists who studied Kalenjin and Danish boys found that the physiological advantages Kalenjin boys have are longer legs and, perhaps more influentially, thinner legs all the way down. Because the leg works like a pendulum, the less weight there is at the bottom (distal weight), the less energy it takes to swing the leg. As Epstein says, “when they were using the same proportion of their oxygen-varying capacity, the Kenyans were going faster for that same effort” (198).

Kalenjins possess an “extreme of a slender body build” (199) known as Nilotic build, referring to populations from the Nile Valley. This body type, therefore, isn’t unique to the Kalenjins, whose ancestors came from southern Sudan before migrating north to modern Kenya. As Epstein notes, however, “long-distance runners from Sudan are almost absent from international competition” (199). Epstein, and the athletes and journalists he spoke to, explains this in terms of sociocultural causes: discrimination within Sudan (now South Sudan) against athletes from the south, and a near-50-year civil war that left “no sports culture or infrastructure whatsoever in southern Sudan” (200). Epstein embarks on an unofficial study of his own on the “‘Lost Boys of Sudan’ […] who fled the violence that engulfed their homes” (200), 3,600 of whom settled in the United States in the year 2000. From this group came several distance runners who won titles in college tournaments and beyond.

One statistician posits that “80 out of every 1 million Kenyan men have world-class running talent, compared with about 1 out of every 20 million men in the rest of the world” (201), but Epstein argues that these projections “do not shed much light on whether the natural gifts required for world-class running are more prevalent among Kenyans” (202). He presents data that shows that other countries, once powerhouses in distance running, have produced fewer world-class runners in the last few decades as those countries have grown “increasingly wealthy, increasingly overweight, increasingly interested in other sports, and increasingly less likely to train seriously in distance running” (202). 

Epstein opens Chapter 13 with a story about a Kenyan 24-year-old named Evans Kiplagat who trains in long-distance running in the hopes of rising out of poverty. In Kenya, the average income is so low that elite runners who bring home prizes can “become one man or one woman economies” (206). As Epstein puts it, “the result of these economic incentives is an army of aspiring runners who undertake training plans fit for Olympians” (206).

Yannis Pitsiladis, the researcher from Chapter 10 who studies the DNA of elite runners, has found something in common amongst professional runners from Kenya: “81 percent […] had to run or walk a considerable distance to and from primary school as children” (207). The Oromos in Ethiopia, who also produce top runners, are another “traditionally pastoralist ethnic group” (208). As Epstein says, a childhood spent running is not necessary or sufficient to become an elite runner, but in a culture in which it’s common for children to run, those with genetic advantages will emerge. Pitsiladis calls it a “socioeconomic phenomenon.”

Pitsiladis also believes Kenya’s high altitude plays a role in Kenyan sprinting dominance. Research into populations with ancestries at high altitudes—in the Andes and Himalayas, for example—reveals that different populations developed different genetic adaptations for survival at high altitudes, and not every adaptation is suited for running. Experts theorize that there’s a “sweet spot” for altitudinous training for athletes, and Kenya and Ethiopia occupy that sweet spot. Epstein concludes that “a helpful combination, perhaps, is to have sea-level ancestry—so that hemoglobin can elevate quickly upon training at altitude—but to be born at altitude, in order to develop lung surface area, and then to live and train in the sweet spot. This is exactly the story of legions of Kalenjin Kenyans and Oromo Ethiopians” (215). It’s also the story of American runner Anthony Sandoval, whose running journey Epstein profiles in detail and who is said to resemble Kenyans in his physiology.

Epstein closes by saying, “just as it is tough to find genes for height—even though we know they exist—it is extraordinarily difficult to pin down genes for even one physiological factor involved in running, let alone all of them” (222).