Crosstalk is a monthly column on the history and philosophy of science.
“The fault Brutus lies not in our stars, but in ourselves that we are underlings.”
– Shakespeare, Julius Caesar
Another thrilling Olympic season passes and we marvel at the prowess of Michael Phelps, Usain Bolt and Mo Farah as they defy age and expectations to consolidate their superhuman status. We admire the new stars emerging and also cheer on our favourite underdogs, who, despite all their circumstances, overachieved enough to defy belief. Expectedly, the disappointment of Indian athletes not crossing that final medal hump has prompted several post-mortems, including the usual murmurings of how Indians are genetically not cut out for physically competitive athletic sport. Most of this does not rest on any scientific fact but only on hyperbolic conjecture. But we can use this as an excuse to understand some of the genetics (if any) of super athletes and look at the likelihood of having many such people in India.
Finding super-humans has been a human obsession for millennia, be it mythical heroes who slayed monsters and moved mountains or through the Olympic games themselves in ancient Greece, where the “best” specimens of Greeks competed in the arena. In recent times, the Nazis created a system to breed “super race” children, with perfect white “Aryan” features (by euthanising or eliminating children with non-desirable characteristics). Thankfully, the myth of white Aryan supremacy was shattered by Jesse Owens in the Berlin Olympics. Meanwhile, the American comic book writers Joe Simon and Jack Kirby imagined Captain America, the weakling turned super-athlete, to combat the Nazis.
Are super-athletes actually born and not made? If so, what kind of genetic abilities help make super athletes, and what more is there to it?
Truth be told, all attempts to explain superior athleticism in ethnic groups based on genetics (or even culture) are largely unscientific. Given the genetic diversity within humans, it is impossible for a “super race” to exist. However, what can definitely occur are genetic traits in individuals that might make that individual more suited (than average) for a particular activity. For primarily skill based sport (everything from fencing and shooting to tennis and football), there really cannot be any genetic attributes that will help. The only things that help are some talent, skill, practice, dedication, perseverance, the right training and mental attributes. But for some sports that require unique physical attributes, there are a few genetic attributes that will help, and these have been called super-genes.
What are super-genes?
David Epstein writes extensively about the perfect athlete in his book The Sports Gene, discussing many now-famous genes like ACTN3, myostatin, ACE1 and EPAS1. What are these genes and what do they do differently in elite athletes? Perhaps the most famous example is ACTN3. This gene makes a protein called alpha-actinin, which is found in humans. In skeletal muscle, there are two types of fibres: fast-twitch and slow-twitch. The slow-twitch fibres are very efficient at using oxygen to generate energy while the fast-twitch, which is inefficient at using oxygen to make energy, can create more force by firing faster and consuming more energy. Sprinters need fast-twitch fibres while long-distance runners need very efficient slow-twitch fibres.
It turns out that ACTN3 is mostly found in fast-twitch muscles and helps them work very efficiently. However, many humans have a mutation in this gene, a single nucleotide polymorphism (or SNP), that makes the gene non-functional and so won’t have ACTN3 protein. This makes their fast-twitch fibres less efficient. On the other hand, humans who have two copies of ACTN3 are likely to have more effective fast-twitch fibres and so become better sprinters. Similarly, the complete loss of ACTN3 makes you more metabolically efficient, and makes your slow-twitch fibres more effective.
But having ACTN3 functioning, as we will see in a bit, is completely insufficient to make you a champion sprinter because of the numbers. The story is similar with other super-athletic genes like myostatin (which helps build bigger, stronger muscles) or EPAS1 (which helps people better adapt to low oxygen conditions at higher altitudes). All of these are overrepresented in different populations: for example, the ACTN3 gene in people of West African descent, the EPAS1 in several high-altitude populations like Tibetans, etc.
But how do we understand the cause and functioning of such mutations? Ironically, one of the best ways to understand these SNPs might be to look at a mutation that doesn’t make you superhuman but actually causes a devastating disease. Sickle-cell anaemia is a rather severe disease present across populations in Africa, the Mediterranean and Arabia, Iran and India. We all know that red blood cells carry oxygen (using a molecule called haemoglobin), and a single mutation in the globin gene changes the haemoglobin protein just so slightly. This in turn slightly alters its ability to bind to oxygen.
Since humans have two copies of all genes, if this mutation is there in only one copy of the globin gene, and the other copy is normal, there is no visible effect in the red blood cell because the normal gene makes half the haemoglobin and such people are carriers. But if both genes are mutated, the red blood cells become fragile and sickle-shaped, and prone to breaking easily. The consequences are terrible.
Why did this disease persist in a population? It so happens that the populations prone to sickle cell are in regions endemic to malaria (sub-Saharan Africa, Arabia, the Mediterranean, India). Malaria is caused by a parasite that lives and reproduces inside red blood cells. If the red blood cell is prone to breaking easily, the malaria parasite cannot reproduce effectively, so such a person is resistant to malaria. So people with one copy of the mutant globin (the carriers), who have some defective red blood cells but are mostly ok, are a little resistant to malaria, but don’t have the devastating forms of the disease. This gives them a survival advantage in malaria-endemic regions compared to others. Unfortunately, those who have two mutant globin genes suffer the disease, so a fine balance decides if the mutation is advantageous or not.
It is largely the same with the super-genes. Depending upon whether none, one or two copies of the functional gene are present, and whether the advantages are greater than the disadvantages and what selective advantage was provided by this mutation, the mutation might persist or become overrepresented in a particular population.
There are two ways by which a certain genetic trait can become prevalent in a population. Most – like in the sickle cell anaemia example – provide a small survival advantage for a particular population, which over time will increase in that population. So these become prevalent over time by natural selection. Of course, having sickle-celled anaemia today in, say, African American populations in the US (a country where malaria has been eradicated) is not an advantage at all. Over time, through natural selection and if allowed to run its course, the percentage of African Americans with sickle cell anaemia will decrease compared to those in Africa, where malaria remains endemic. Artificial selection, where individuals with certain traits are constantly bred for, is one other way. If sprinters only marry sprinters for many generations, their offspring are likely to be even better sprinters.
Common genetic traits v. outliers
What needs to be remembered is that at a population level, there will be enrichments (or overrepresentations) for genetic traits. Let’s take the example of Jamaican sprinters. Most Jamaicans are of West African descent (having been brought centuries ago to the West Indies as bonded or slave labor). This population has an enrichment for SNPs like ACTN3 or ACE1 that build fast-twitch muscles, and helps in sprinting. Let’s say this is present in 50% of these populations compared to a 5% worldwide average prevalence (these are hypothetical, exaggerated numbers, but would be considered HUGE overrepresentations for a geneticist).
This means about a million and a half Jamaicans have this mutation. But perhaps only a few hundred of them would ever be able to actually run 100 meters in the 10-second-range, if they were spotted early enough and spent years in single-minded training. That is because this gene is a necessary requirement for sprinting but is not in itself sufficient. This tiny number then is less than 0.1% of the population and statistically insignificant. Yet Jamaica produces an endless stream of superb sprinters. That is because the success of a few has resulted in a culture of sprinting, and a system that identifies and trains sprinters very successfully. You have an ecosystem for sprinting success. Jamaica massively outperforms the much larger population of all of West Africa in sprinting, where the genetic advantage is actually endemic.
Now, let’s take a very large population – India’s. There might be a strong selection bias against, say, the ACTN3 SNP or other SNPs that help make great sprinters. So using those same imaginary numbers, we can use a number like 1% of the population with the mutation, which is a huge underrepresentation of the worldwide average. But for a larger population, that will mean a huge number of people (over 15 million, more than five-times the population of Jamaica) with this mutation. Now genetically normalised, there will be 10-times as many people in India who can potentially run a 10-second 100-meter race – but only if they were identified early enough and entered an appropriate lifetime of training and conditioning.
Given this information, every elite athlete (regardless of country of origin or race) in the world is likely to have mutations or SNPs considered required for super-performance. At that level, there will be little genetic variation since this is a selection by whittling down numbers beyond statistics. This will be the nature of all genetic outliers, which will always come down to prevalence in a population along with the population size. So for athletics, it is a simple enough numbers game, where if there is a large enough society with a supportive-enough system for sport (and a means to identify and efficiently support individuals), this society will dominate athletics.
The key to athletic success therefore comes from having sufficiently efficient systems and resources to support such athletes, and the athletes themselves putting in the appropriate quality of 10,000 hours. This is why the US will remain dominant in athletics, and why China over the past decades has become a powerhouse. To complete the example, the average East Asian is not built for sprinting. But with an efficient system, China has produced individuals (like Su Bingtian) who can run a sub-10-second 100-meter race. In fact, both China and Japan were competitive in the sprints at Rio (Japan won the silver at the 4 x 100 relay and China finished fourth).
Coming full circle: for the purely physical sports requiring specific attributes that can be genetic, what of India and Indians? Given the population size, and the fact that the Indian populations are amongst the most genetically diverse in the world (a healthy mix of almost all racial types thanks to location and history), pretty much every single desirable and undesirable genetic trait is probably there in substantial numbers. But the likelihood of finding a super-athlete will remain low because of our own systemic failures to provide environments and conditions that encourage even basic sports, leave alone champions.
Sunil Laxman (@sunillaxman) is a scientist at the Institute for Stem Cell Biology and Regenerative Medicine, where his research group studies how cells function and how they communicate with each other. He has a keen interest in the history and process of science and how science influences society.