Thirty-five years ago, a hundred tennis-playing children were tested for general athleticism. One girl was rated by the psychologist leading the analysis as “the perfect tennis talent”. She outperformed her contemporaries at every tennis drill, as well as general motor skills. Her lung capacity suggested that she could have become a European champion at 1,500 metres. The girl’s name? Steffi Graf, who went on to win 22 grand slams.

I was reminded of Graf’s innate sporting talent during a recent conversation with the geneticist and former Economist journalist Matt Ridley. We were discussing the common argument that greatness, even genius, is the result of 10,000 hours of dedicated practice. This has been the sales pitch of several widely read books, the subtitles of which include “The genius in all of us” and “Greatness isn’t born, it’s grown”.

If nurture is so dominant and nature such an irrelevance, then an unavoidable question follows: how many people, of all those born in 1756, had the potential, if they were given the right opportunities, to be as good as Mozart? Or in this case, how many women, of all those born in 1969, had the potential to become as good at tennis as Graf? According to the logic that a genius lurks in all of us, the answer must lie somewhere between “most” and “many”.

Ridley’s answers were a bit different: four Mozarts and about 30 Grafs. There was mischief, of course, in attaching numbers to such hypothetical questions. But his answer rang true.

The surprise here is that the idea of talent finds itself on the ropes, beaten and bruised by those who believe in nurture alone. Acknowledging a role for genes, any role, can feel almost immoral. When I was quizzed by a newspaper about the genetic arguments in my book “Luck”, the interviewer sounded surprised — even though he agreed — that I dared to take on the gene-denial industry. His reticence was understandable. The anti-genes lobby often suggests that it is a short hop from recognising the existence of genetic talent to believing in eugenics. Personally, I’m pretty confident we can distinguish between the two.

The role of innate talent in elite sport, just as it has been written out of the causal narrative, is actually in the ascendant out on the pitch. Consider the example of modern tennis. In the late 1970s and 1980s, tennis was still catching up with the implications of professionalism. John McEnroe enjoyed going for a burger much more than going to the gym. It fell to the underrated Ivan Lendl, a less talented all-round player than his elite rivals, to dedicate his whole life to the pursuit of self-improvement. To protect his joints, Lendl pioneered aerobic training on bikes rather than road running. He even installed an exact replica of the court at Flushing Meadow, home of the US Open, in his own back garden in Connecticut. Less gifted than McEnroe, Lendl relied on being fitter and more prepared. He used nurture, if you like, to make up for a shortfall in nature. And it worked. Lendl overhauled his rivals and spent 270 weeks as the world number one.

One up for nurture. But what if all the top players hire nutritionists, masseurs and specialist coaches? That is what happened within 20 years. The upshot was that for 302 weeks between 2004 and 2009, the world number one was Roger Federer, widely rated the most talented player ever to pick up a racket. This view hardly needs anecdotal support, but if you’re sceptical, perhaps you can take his greatest rival’s word for it. “His DNA”, Rafael Nadal says, “seems perfectly adapted to tennis.”

During the amateur era and the early decades of professionalism, tennis players came in all shapes, sizes and training regimes. So it was possible to gain a significant edge through sheer hard work. But when a sport becomes fully professional and global, and nurture equilibrates, nature once again has the upper hand.

In youth sport, evidence is mounting that the 10,000-hour paradigm, based on a questionable experiment of the early 1990s, is now doing serious harm. First, it has entrenched a feeling of misplaced entitlement among kids who end up depressed and disorientated because they did not, after all, become the new Tiger Woods, despite putting in the hours. Secondly, it has reinforced the delusions of another type of tiger: the maternal variety. Parents increasingly view bullying their children into intense athletic training as a rational pension plan for themselves. Expect some future tensions here. Thirdly, specialising is proving counter-productive, even in the relatively narrow field of acquiring skills. A 2011 study of 243 Danish athletes found early specialisation to be either entirely irrelevant or actively detrimental. When teenagers are still growing and muscles developing, the evidence now suggests that they are better off having a broad sporting education — just as their minds develop better on a varied diet of academic subjects.

The balance is finally swinging back to common sense. David Epstein, author of the solidly researched book “The Sports Gene”, pinpoints an eclectic array of genetic influences. A high belly button, for example, is correlated with success at sprinting; a low belly button with an aptitude for swimming.

None of this undermines the importance of hard work. All sporting stories rely on the subtle interaction between nature and nurture. But success relies just as much on finding your niche, the right lock for your key, as it does on blind perseverance. Older brothers and sisters help too — because they introduce you to games young, drag you up to their level, and, unlike many parents, believe in brutal honesty. At the age of eight, I toyed with trying to play football for England, rather than cricket. “Waste of time,” said my older sister, “you’re not fast enough.” And she was right. But why didn’t she suggest golf?