Does nature or nurture make a top sprinter?

Reuters – 3 hrs ago LONDON (Reuters) - The dominance of Jamaicans and Americans of west African and Caribbean descent in world class sprinting has sparked intense debate about whether running at speeds that push the limits of what is humanly possible is all in the genes.

It is an idea that has its attractions. After all, it does seem baffling that the tiny island nation of Jamaica with a population reaching barely 2.8 million can consistently produce world-beating sprinters, while the whole of Europe can hardly register more than a handful of athletes in the top 100.

Yet sports scientists and geneticists say pinning sprinting success purely on nature rather than nurture is overly simplistic and ignores a wealth of cultural and societal factors that are equally important to beating the clock.

"What we know about genes in sport is that genetic make-up accounts for about 50 percent of variability in baseline performance," said Ken van Someren, director of sports science at the English Institute of Sport.

"What that basically tells is that sports performance is a combination of both nature and nurture."

SPRINTING GENES?

Bengt Saltin, a professor of human physiology at the University of Copenhagen's Muscle Research Centre in Denmark, says the balance of fast twitch to slow twitch muscles is key.

Fast twitch fibers produce the same amount of force for each contraction as slow muscles, but they get their name because they can fire far more rapidly - making them better for explosive, fast and forceful sports such as the 100m final.

And while training and practice can obviously improve muscle performance, evidence suggests slow twitch fibers cannot be converted into fast twitch, meaning that what athletes have is what their genes gave them.

"If you don't have at least 70 to 80 percent fast twitch muscle fibers, I'd say it's unlikely you could be among them (the world's top sprinters)," Saltin told Reuters.

"But if you have that kind of level you could probably do well - and if you have 80 to 90 percent that's even better."

A flurry of excitement about the idea of genes for athletics prowess took off in 2003 when Australian scientists found that a gene called ACTN3 has certain variants which may give the muscles of elite athletes a performance advantage.

Their study, published in the American Journal of Human Genetics, found that ACTN3 could give sprinters a boost because it gave extra power to fast twitch muscles.

Studies show this version of ACTN3 - dubbed the "sprint gene" - is more common in Jamaicans and other people of West African descent than in people of European ancestry.

Scientists are keen to point out, however, while the "right" kind of genotype is likely to be more prevalent among successful sprinters, for example, than among the general population, there is also likely to be wide variation between genetic profiles of those at the top of the sport.

"The closer towards elite you get, and the closer towards the limits of performance, so genetic make-up may well put some sort of glass ceiling there," said van Someren.

"But there is no single gene that accounts for speed and power, or for sprinting. From what we know so far it appears to be a really complex interaction of lots of genes.

So it's impossible to say there's a west African genotype for sprinting, or an east African genotype for endurance running. Genes only play a part."

BEYOND THE GENOME

Scientist say any gene-centered explanation also dismisses the importance of a whole host of psycho-social and cultural factors that are likely to be major contributors to the success of Jamaican sprinters.

Track and field holds a position of high respect in Jamaica. The annual school athletics championships, known as Champs, is a major national event whose significance ranks with the Super Bowl for Americans or the FA Cup final for the English.

Experts also note Jamaica's investment in an infrastructure and training system to pick out and nurture potential elite track athletes, a culture that idolizes sprint heroes, and a powerful desire among young Jamaicans to use sport to lift themselves and their families out of poverty.

"They have role models and opportunities, it's a fun, sociable and competitive event from a very early age, and it has great rewards, both financial and social," said van Someren.

Daniel MacArthur, one of the researchers who published the 2003 paper linking ACTN3 and sprinting performance, says he regrets the study has led to far too much emphasis being put on what some like to see as an evolutionary advantage.

"It is almost certainly true that Usain Bolt carries at least one of the 'sprint' variants of the ACTN3 gene," he wrote in a science blog about the issue. "But then so do I - along with around 5 billion other humans worldwide.

"That doesn't mean you'll see me in the 100 meter final in London in 2012. Unfortunately for me, it takes a lot more than one lucky gene to create an Olympian."

(Editing by Alastair Himmer)

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Feces fossils show connection between Native-Americans, diabetes: Did fat-hoarding genes develop from the nature of ancient feasts?

ScienceDaily (July 24, 2012) — Why do Native Americans experience high rates of diabetes? A common theory is that they possess fat-hoarding "thrifty genes" left over from their ancestors -- genes that were required for survival during ancient cycles of feast and famine, but that now contribute to the disease in a modern world of more fatty and sugary diets.

See Also:Health & MedicineNutritionDiet and Weight LossCholesterolFossils & RuinsAncient CivilizationsArchaeologyFossilsReferenceDiabetic dietSouth Beach dietGlycemic indexMediterranean diet

A newly published analysis of fossilized feces from the American Southwest, however, suggests this "thrifty gene" may not have developed because of how often ancient Natives ate. Instead, researchers said, the connection may have come from precisely what they ate.

The research, which appears in the latest edition of the journal Current Anthropology, suggests that the prehistoric hunter-gatherer civilizations of the Southwest lived on a diet very high in fiber, very low in fat and dominated by foods extremely low on the glycemic index, a measure of effects food has on blood sugar levels. This diet, researchers said, could have been sufficient to give rise to the fat-storing "thrifty genes."

"What we're saying is we don't really need to look to feast or famine as a basis for (the genes)," said Karl Reinhard, professor of forensic sciences at the University of Nebraska-Lincoln's School of Natural Resources and the study's lead author. "The feast-or-famine scenario long hypothesized to be the pressure for 'thrifty genes' isn't necessary, given the dietary evidence we've found."

Natives have some of the highest rates of Type 2 diabetes of any group and are more than twice as likely to develop the disease as are Caucasians. The notion the gene's origin goes back to feast-and-famine cycles among prehistoric hunter-gatherer ancestors has been discussed for nearly a half-century.

To fully understand the basis of the high rates, Reinhard said, "one has to look at the best dietary data one can find. That comes from coprolites (the official term for fossilized feces). By looking at coprolites, we're seeing exactly what people ate."

The coprolites are from Antelope Cave, a deep cavern in northern Arizona where, over several thousands of years, was home to various cultures. That includes the Ancestral Pueblan peoples, who are believed to have lived there seasonally for at least 450 years.

Reinhard and Keith Johnson, an archeologist at California State University, Chico, studied 20 coprolites found in the cave and combined it with analysis from other sites for hints of ancient Natives' diets. They found clues to a food regimen dominated by maize and high-fiber seed from sunflowers, wild grasses, pigweed and amaranth. Prickly pear, a desert succulent, was also found repeatedly in the samples.

By volume, about three-quarters of the Antelope Cave coprolites were made up of insoluble fiber. The foods also were low on the glycemic index; some research suggests that high-GI foods may increase risk of obesity and diabetes.

The analysts' findings led them to deduce that the nature of the feast, and not necessarily its frequency, was enough to lock the "thrifty" genes in place -- and leave modern Natives more susceptible to diabetes as their diets evolved to lower-fiber, higher-GI foods.

"These were not just famine foods," the authors wrote. "These were the foods eaten on a day-by-day basis during all seasons in both feast and famine. They continued to be eaten even after agriculture was developed. Antelope Cave coprolites show that this high-fiber diet was eaten during the warmer seasons of food abundance."

In addition to UNL's Reinhard and California State Chico's Johnson, the study was authored by Isabel Teixeira-Santos and Monica Viera of the Escola Nacional de Saude Publica in Rio de Janeiro, Brazil.

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