The Sports Gene:Inside the Science of Extraordinary Athletic Performance

Date Reviewed
January 20th 2014

I don't recall ever having read a non-fiction book that was such a page turner. Part of that certainly is my personal interest in the subject, but David Epstein, a senior writer for the magazine Sports Illustrated, has not unexpectedly, a great storytelling knack. He employs it regularly at the outset of every chapter as well as within them to introduce heavier material more painlessly.


The term “sports” in the title, certainly is valid and colloquial to draw a readership in, but the subject is basically about primal genes of athleticism. But he does briefly venture into genetic contribution to pain tolerance and mental and emotional characteristics that can optimize performance. One's willingness to train, or not, may also be genetically inspired.


However, the environmental aspects of developing talents is certainly dealt with. In allowing the subject a modern lingo, Epstein refers to the genetic heritage as the “hardware” and the environmental as the “software”.


He delves into such subjects as the Jamaican sprint hothouse and Kenyan equivalent in middle and long distance running. And he spends time in both of these places giving further credence to his observations and comments. Along with that he regularly incorporates scientific findings broadly selected from studies around the world.


In the early part of the 20th century it was thought there was one ideal sports physique for all sports, specialization and training shows this not to be the case. Shot putters have been getting bigger while distance runners and gymnasts smaller.


“But the winner take all effect (huge salaries), combined with a global marketplace that has allowed many more people to audition for the miniscule number of increasingly lucrative roster spots, has indeed altered the gene pool. Not the gene pool in all of humanity, but certainly the gene pool within elite sports.”


A recent paradigm, the 10,000 hours to mastery of something, popularized by writer Malcolm Gladwell in his book 'Outliers' is challenged fairly convincingly.


Not only are the obvious natural talents investigated, but also the less obvious, that in many people may remain undiscovered.


For those with an amateur interest in genetics and the consequences of the unravelling of the genome intriguing aspects are brought forward, in some cases profiled convincingly and in others, hinted at.


An interesting perspective relayed is that “white people all look alike” same with Asians and natives of the western hemisphere are even more identical. It is the blacks who show the greatest variability. And that is because the human gene pool did most of its evolving in Africa. The migrant streams that flowed intermittently out of Africa were small and as such took a limited sample of genetic material.


That limited stream was parsed to an even smaller selection when people migrated out of Asia to the Americas.


Certain characteristics were reduced, eliminated or emphasized by natural selection, often according to the environment in which the people lived. In addition, mutations of genes continue to occur some taking hold in populations and others not.


While there is little reluctance to explore genetics revolving around gender, there is, said Epstein, with race, where political implications discourage the publishing of some research.


And while there are 'hotbeds' of certain genes they can occur almost anywhere, if with less frequency. A tall basketball prospect may come from the diverse gene pool of the pygmy community (where men average 5 feet tall) but the likelihood isn't worth planting an NBA scout there.


One researcher thought she had pinned down the “speed” gene. The gene proved to be absolutely essential, but by itself didn't guarantee speed. Other genes in combination were needed, as is the case with many characteristics.


In conclusion, Epstein says there is no single gene for sports or even a consistent pattern of combinations. The closest to a single transcendent gene mutation was found in a Finnish cross country skier who won seven olympic medals in the 1960s and retired possibly before reaching his peak.


There was a “minor” variant in one gene in “the 19th chromosome” that allowed him to produce far more than the average amount of hemoglobin. In effect, he naturally had a condition that professional cyclists, will risk death and banishment for... more oxygen carrying ability in the blood. While it can be life threatening through compromising circulation, this man remains healthy.


And there is no doubt, says Epstein, that the environment is what may allow the genetic “gifts” to bloom or not and as such, is equally important.


I know nothing about, nor have read anything, about dogsled racing before being immersed in a chapter in this book. The key point is that the dogs won't run nearly to death for reward or to escape punishment. They run because they like to, says Epstein. The reward may be hormonal and pleasurable.


One annoyance that I encountered was the use of the phrase “exact same”. This redundancy should be axed by any editor paying attention, unless couched in a direct quote.


Maybe more than any other review I have done, putting the meat on the bones of the generalities outlined above is compelling.




We are drawn into the story with the chapter title “beat by an underhand girl”. Those beat by the softball pitcher are the best hitters in major league baseball and they were all hapless against her. She is throwing from softball distance so her 60 mph gets on them like a 95 in hardball, but it is a bigger ball.


From here Epstein discusses the key attributes of a hitter in baseball and it isn't reaction time, some are actually quite pedestrian in that area. The crucial aspect is how quickly they can perceive what is being thrown.


This comes from recognizing arm angle, body position and other features they have unconsciously absorbed over the years. “Watch the shoulder” is more relevant than “keep your eye on the ball”. The underhanded pitch makes all this learning largely useless.


However, this early recognition of what is happening is crucial in sports where reaction time is critical. But this is also a characteristic of the 'good' versus the 'mediocre' chess players, also a function of familiarity with the game.


One of the most important characteristics for hitting a baseball is eyesight, visual acuity in all its aspects. And in fact good hitters in baseball and softball have the best eyesight of any athletes, with archers and tennis players close. Fencers are strong in depth perception.


Normal good eyesight is described as 20-20 which means one can see at 20 feet what one is supposed to see at 20 feet. Baseball hitters are regularly 20-13 and better (that is can see at 20 feet what the 20-20 can see at 13) some approaching the theoretical human limit of 20-8 with many around 20-10. Epstein terms it 'major league vision'. It allows them to pick up on the relevant cues sooner making reaction time less crucial.


Mike Piazza, one the best of hitting catchers, was tagged while in minor league obscurity by an optometrist as having hitting potential based on eyesight.


While the 10,000 hours of practice to mastery may be valid in some sports it varies from sport to sport and person to person.


In his 'Tale of Two High Jumpers' Epstein details the decades long practice and honing of technique by Swedish high jumper Stefan Holm, winner of the event at the 2004 olympics. At less than six feet tall with a relatively ordinary vertical jump ability, he utilized conversion of speed and good technique and “draping” to clear the bar without actually getting his centre of gravity to the height of the bar.


Still near his prime, he lost the 2007 word championships to Bahamian high jumper Donald Thomas. Thomas a 'basketball addict' with a great vertical jump,was goaded into trying high jumping on a dare that he couldn't convert his ability. His first time out he jumped 7 feet and was convinced to try track. With less than a year of haphazard training he bested Holm. His style was stiff and as such his centre of gravity over the bar, once measured beyond 8 feet, inches above the height cleared, was consistently higher than the fluent Holm. He never improved much nor reached the ultimate height of Holm, but his raw jumping ability put him in the same league with less than 1,000 hours of training.


The physical characteristic the two had in common was exceptional development of the achilles tendon. Both had thick stiff tendons, but Thomas' at 10 inches, was extraordinarily long for his height. It is believed that 'spring' is stored in minute stretching of the tendon at takeoff. While training can increase the thickness and stiffness, there appears to be a strong genetic component.


As well as having the “right” genetic makeup and the environment a person must be guided into a sport at the right time. Often, says Epstein, that seems by the age of 12 so that crucial neuromuscular connections are reinforced before the opportunity is lost. An athlete may gain the masters level starting later but it is less likely. It is the case with much learning. There is an optimum time for the brain.


This was an explanation given for why Michael Jordan, an extraordinary athlete, could not learn to hit a baseball well.


Specialization, with intense training too early at the expense of general development, can lead to an early plateau.


Epstein has some interesting information on gender biology in sports. “The trouble is that human biology simply does not break down into male and female as politely as sports governing bodies wish it would.”


It seems there are combinations beyond just the XX and XY chromosome paradigm with additional Xs and Ys and various combinations of gender organs. Then there is the “testosterone” problem. Some women have an unacceptable, to sports bodies, level of testosterone, but in one case sighted by Epstein, the female runner's body could not utilize it, so there was no advantage.


Men are favoured over women structurally in throwing because of a longer forearm and in running because hips are narrower. Boys being exposed to testosterone in the womb are generally better at visually tracking and intercepting flying objects.


This all translates into a 30 per cent advantage in throwing speed for men and an 11 per cent advantage for running at all distances and 19 per cent in the long jump, all based on elite performance.


The narrowest gap is in the 800 m. swim where women are only six per cent behind men, again using elite standards.


From the 1950s to the 1980s women runners were closing the gap, but efforts plateaued, while men incrementally are pulling away.


Women's wider hips, leading to a greater knee angle makes them more susceptible to anterior cruciate ligament tears. Wider hips also lead to more wasted energy in running.


And then there is the difference in muscle mass. Men have 80 per cent more in the upper body and 50 per cent more in the legs. More muscle mass is packed into a given space in men than in women. In addition men's muscles respond faster to weight training and the heart to endurance training.


His story on 'trainability' (how quickly the body responds to training from the baseline is also genetically influenced) profiles a boy about to enter high school and searching for a sport that he can succeed at. Although taller than average, no other aptitude stood out. He went out for the cross country team as a sophomore.


However, 40 years later he was picked over Tiger Woods and Lebron James as the greatest American high school athlete of all time. Jim Ryun, the dominant middle distance runner of the late 1960s was the first high school student to run a sub-four minute mile. He thrived on “crushing” workouts.


Ryan had the two genetic advantages. He had a natural high aerobic capacity (VO2 max), but maybe more importantly it increased rapidly with training. Some may have a high VO2 max yet not respond much to training.


British triathlete Chrissie Wellington, who had astounding feats in her sport, with comparatively little training, but rapid improvement, seems one of those “naturally fit” people. Blood volume capacity of the heart seems part of the condition.


This innate ability to respond to training muddles the notion of innate ability prior to training.


The genetic influenced response to training underlines the idea that there is no one-size-fits-all training plan.


As with aerobic training, people have different rates of response to muscle building training. In the case of muscle building, the presence of satellite cells waiting near muscle fibres to be activated seems common.


Fast twitch muscle fibres (explosive but tire quickly) grow twice as much as slow twitch. Hence the more fast twitch muscle fibres in a muscle the greater the growth potential. A turkey or chicken dinner allows you to recognize the fast twitch muscle, the white meat, and the slow twitch, the dark meat. Slow twitch require abundant oxygen hence more blood vessels making the muscles darker.


Most people have slightly more than half their muscle slow twitch. However, athletes have percentages favouring their sport. Sprinters may have 75 per cent fast twitch in their calves where half milers are nearer 50 per cent. It is not certain whether the sport selected causes the development or whether the development causes the selection of sport.


Aerobic training may make fast twitch muscles more endurant and weight training make slow twitch muscles stronger.


A high proportion of fast twitch muscles means less tolerance for training. And the fastest athletes are more likely to get injured, often hamstring. Also a high proportion of fast twitch muscles make losing weight harder than for people with more slow twitch muscle, whose fuel is fat.


One's success can depend on the sport that best matches up with the proportions of fast and slow twitch muscles.


As with muscle types, variation in limb length (levers) for different sports is needed. Ironically football recruiters make a common mistake in early selection of football players. They use the bench press as a standard for strength. However, that lift favours the athlete with shorter arms and everything about football favours longer arms.


Sticking with football for a minute, cornerbacks and running backs needing speed and agility have been getting shorter over the last forty years while humanity has been getting taller.


One of the most profound body type anomalies was British marathoner Paula Radcliffe who at 5'8” was literally head and shoulders above the competition, but her wins were predominantly in the cooler seasons, when she was nearly unbeatable. Her greater size made it more difficult for her to 'unload' heat during a race, making it harder to win in the summer, coincidentally when the Olympics are held. She never contended at either of her two Olympics.


Swimmers have an interesting combination of proportions. Long arms, large hands and feet and a long torso with comparatively shorter legs are ideal. One swimming coach told me that is a perfect description of swimmer Michael Phelps.


Wrestling and weightlifting favour shorter arms and paddling events long arms. All running favours longer legs. Those with African ancestry have longer legs and narrower pelvises than Europeans. While there are racial predispositions to certain proportions, exceptions can occur anywhere in the world.


As well as lever lengths, the amount of bone also limits muscle mass. Generally the human limit is five times as much muscle mass as the weight of the bones supporting it. Individual bone mass can respond to exercise increasing the amount of muscle that can be supported. This is prominent in the racquet arms of tennis players.


Not many sports are helped by being a bit fatter. Shot put is one where extra body mass offsets the weight of the shot and the distance travelled in the put is short.


Because the world is now so successfully scoured for the ideal body types, records will now increase more slowly.


While basketball recruiters focus on height, that may be an indirect way to get something more crucial...height reached which is a combination of height and “wingspan” (distance between fingertips with arms stretched to the side). Manute Bul, recruited from the Dinka tribe of Africa, was more than 7'5” inches tall but what capped it off was a wingspan well in excess of 8 feet.


Body proportions are the result of genetic selections for the environment. Long limbs add more skin hence more cooling for those living in the tropics. Conversely short limbs conserve heat for those living near the Arctic.


In his chapter 'We are all Black (Sort of)', Epstein elaborates on the genetic variation in Africa compared to the other parts of the world. “There is more genetic variation among Africans from a single native population than among people from different continents outside of Africa. On one particular stretch of DNA, geneticist Kenneth Kidd observed more variation in one population of African Pygmies than in the entire rest of the world combined.” However, there are certain genes where there may be more diversity outside of Africa. Gene selection and emphasis did continue after leaving Africa.


“Essentially every modern human outside of Africa can trace his or her ancestry to a single population that resided in sub-Saharan East Africa as recently as ninety thousand years ago.”


This African diversity suggests that not only may the fastest humans and highest jumpers be from Africa, but the slowest and lowest also, but who measures 'slow' and 'low'? They don't make it into motivational speeches.The same extremes may be the case with most other genes.


At the DNA level humans are 99 to 99.5 per cent the same and 95 per cent similar to chimpanzees. The differences in the latter five per cent are significant.


The Jamaican sprint factory is based on a gene package that came from equatorial west Africa where slaves were secured. Hence it is also in parts of the Caribbean and the Americas.


That it manifests itself so much in Jamaica (more specifically the north west part of the island where the fiercest slaves were brought) seems to be environmental. Sprinting is the best economic option (such as scholarships and athletic career) for speed in Jamaica. And of course now there is a tradition with its own momentum. “Youth track is the rage.”


In the United States, that speed has other more popular and profitable places to go, maybe most notable football.


Almost all Jamaicans have the “that without which not” gene of sprinting , ACTN3, but it is widely spread throughout the world.


Another genetic mutation in the blacks deriving from equatorial west Africa is the sickle cell in the blood. This is an evolutionary response to malaria. When blood is low on oxygen the cell changes shape toward a 'sickle' and in this form it tends to impair blood flow during vigorous exercise. People with this gene mutation are under represented in aerobic endurance sports.


There is a correlation with this low haemoglobin protection against malaria and an increase in muscle tissue relying less on oxygen to create energy. This is quick twitch muscle, ideal for short duration.


There is an evolutionary genetic tradeoff here.


Directly across the continent from the evolutionary base of many of the world's greatest sprinters is the base of the world's greatest middle and long distance runners. The Kalenjin are a tribe in Kenya that lives on the equator at about 7,500 feet on the heights of the Rift Valley.


It may be more than coincidence that their homeland is too high for mosquitoes and hence there is no sickle cell effect on the haemoglobin.


As a herding tribe they engaged in cattle raiding on neighbouring groups, a practice common in East Africa. This often involved running great distances at night.


To put the running prowess into perspective 17 American men have run the marathon faster than 2:10. Thirty-two Kalenjin men did it in the month of October in 2011.


Studies suggested that one of the key advantages of these people is smaller girth of their legs, particularly the lower leg. Since the leg works like a pendulum the amount of effort used to run is a function of the mass of the leg and how far down it is. Weight has a more negative effect on running toward the end of the leg than anywhere else on the body. Large shapely calves may be visually appealing, but they are counter to running. The Kenyan runners also have relatively long legs and long achilles tendons.


As with other people who evolved in equatorial Africa, the Kalenjin, a Nilotic people, have long slender limbs and narrow hips ideal for cooling in hot temperatures. Another Nilotic tribe, the Dinka, with similar long limbs have produced basketball players such as the already mentioned Manute Bol.


A study suggested that 80 out of a million Kenyan runners have the world-class running talent compared to one in 20 million in the rest of the world. If only the Kalenjin were compared, the ratio would be even more extreme.


On the environmental front, those who had dominated distance running, the British, Finnish and Americans got wealthier, fatter and interested in other things.


Correlated with the Kalenjin success is poverty and running as a form of transportation and as a way out of poverty. The stronger foot muscles from running shoeless is also a factor. This is coupled with running as a tradition to emulate, as in Jamaica or Canadians with hockey.


Epstein explains that the normal response to high altitude is an increase in haemoglobin and red blood cells which allows the blood to carry more oxygen, but increases its viscosity impairing circulation hence altitude sickness.


Tibetans are the only people who don't respond this way. A version of the gene EPASI regulates production of red blood cells so the blood does not become thick. Another response is an extremely high level of nitric oxide in the blood which relaxes and widens blood vessels increasing the volume of circulation, particularly to the lungs hence supplying more oxygen. In addition, they breathe deeper and faster.


For the rest of us the sweet spot for altitude training seems to be 6,000 to 9,000 feet. Hard training is impaired above that. This is where the Kenyans and Ethiopians live. Those born there seem to have larger lungs. It is an environmental response, not genetic, but will not occur past adolescence. These responses can occur in other places, but are not so common.


The Kenyan national record in the 100 m. wouldn't make Olympic qualification. The west Africans are comparably hapless in the 10 k race.


Changing direction, Epstein says, each sport has a signature pattern on heart development. Cyclists and rowers have enlarged heart chambers and walls, from their training. Weightlifters have thicker walls, but not larger chambers.


Concussions are big news in North American contact sports. It seems the ApoE4 gene while not making a person more susceptible to concussion, may affect the recovery. But a certain gene may increase the likelihood of 'blowing out a knee'. 'Prehabilitation' may be used to increase the strength of tendons and ligaments reducing the risk.


Flexibility also has a genetic factor. Inflexibility may favour running. Apparently flexible isn't for everyone.


A big one vaguely related to “no pain no gain”. There are genes that effect perception of pain. Also pain is to an extent learned, not just innate. All this makes it hard to know somebody else's pain.


Humans have evolved so to a degree they can block pain in extreme situations. Sports do try to tap into this.


Briefly back to Eero Mantyranta, the diminutive Finn from the Arctic Circle who dominated cross country skiing in the 1960s armed by a single key genetic advantage. Skiing for him was a mode of transportation and an opportunity to escape the lumber camps for a better job as a border guard. When greater incentives were offered from training he embraced that. But he quit skiing relatively early because he didn't really like it or the attention, despite the success.


The rare gene mutation he had were in several other family members, a couple of whom went on to fame as cross country skiers, but none had the haemoglobin concentration he had.


For most activities several genes are at play, says Epstein. It would be extremely rare for any one person to have more than 16 of the 23 believed relevant for endurance. And he cautions that a lot of work goes into exploiting genetic advantage to the fullest. `