Before my Jamaican-born grandfather, Egan “Teddy” Brooks, left Harlem for Scotland in 1935, he was on the track team at George Washington high school in New York. Somebody wrote on his yearbook photo: “Can he run!”
This week’s Commonwealth Games will provide a further demonstration of the Jamaican flair for sprinting. The fact that my grandfather, Usain Bolt and many other Jamaican-born athletes are so fast is, in scientific terms, an anomaly. Anomalies are often the harbingers of a profound scientific insight. So what might we learn from this one? The answer has nothing to do with reinforcing prejudices about the sporting abilities of black people. It’s about facing up to the consequences of past events.
Scientists have looked into the genetics of Jamaican sprinters’ dominance. The first gene associated with powerful sprinting is the angiotensin-converting enzyme, or ACE, gene. If you have a particular variant of this gene (known as the “D allele”) you are likely to have a larger than average heart capable of pumping highly oxygenated blood to muscles quicker than the average human. That also gives your body a better response to training. In people of west African origin, the frequency of the variant is slightly higher than in those of European and Japanese origin. In Jamaica, it’s a little higher than in west Africa.
That is interesting because, of the 10 million people forcibly removed from Africa in the transatlantic slave trade, more than a million died en route. The last stop for the Caribbean slave ships was Jamaica; if you made it this far, you were among the toughest of the tough.
This small effect may be amplified by the ACTN3 gene. This encodes instructions to create a protein called alpha-actinin-3, which helps muscles generate strong, repetitive contractions. Like the ACE gene, it comes in different types. The desirable variant for a sprinter is known as 577RR. While only 70% of US international-standard athletes have the desirable variant, 75% of Jamaicans have it whether they are athletes or not. That gives Jamaica another edge.
There may be another tiny advantage: Jamaican soil. University of the West Indies researchers Rachael Irving and Vilma Charlton discovered that a disproportionate number of Jamaica’s Olympians – including Usain Bolt and Veronica Campbell – come from the region containing the island’s aluminium ore deposits. Even more Olympians’ parents were born and raised there. The ACTN3 gene can only make a difference during the first three months of pregnancy when the number of fast twitch muscle fibres is determined. Irving and Charlton’s suspicion is that aluminium in the mother’s diet promotes the gene’s activity. We already know that aluminium in the environment or diet can alter a gene’s creation of certain proteins. Jamaica’s food crops will contain especially high amounts of aluminium when grown in bauxite-rich soil. If that promotes the development of fast-twitch muscle fibres in growing foetuses, that could add to the Jamaican edge.
The truth is, we don’t have enough information to draw firm conclusions about the Jamaican dominance of sprinting. But there is good reason to dig deeper – and it has nothing to do with athletics. We now have evidence that extreme stress, heat, cold, malnutrition and pollution (including tobacco smoke) trigger changes in the way genes are activated or silenced. Long-term studies of populations in various countries have shown that these conditions can induce adverse health effects that cascade down generations. Slavery is likely to be no different.
One of the effects of slavery seems to be a susceptibility to diabetes, hypertension and other cardiovascular problems. Studies show 35% of all retired Jamaican athletes suffer such afflictions. It’s a similar story in America: nearly half of all African American adults develop some form of cardiovascular disease. According to a paper published in the New England Journal of Medicine in 1990, an African American man in Harlem is less likely than a man in Bangladesh to survive to the age of 65.
The problem has been traced to low birthweights. The descendants of slave populations have suffered persistent low birthweights since the first data was taken in 1897. Becoming more affluent makes no difference, and it is not strictly genetic: the west African population doesn’t suffer a similar problem. Something is different about the descendants of slaves. Epigenetic factors – changes that turn genes on and off – could well be responsible.
We may be risking the health of our children and grandchildren because of unexplored epigenetic effects induced by poverty, poor diet and pollutants. We need to chase down this difficult but important branch of science at speeds even greater than Bolt – and maybe my grandfather – could manage.
Michael Brooks is a consultant for New Scientist and the author of 13 Things That Don't Make Sense and At The Edge of Uncertainty.