During the 2016 Summer Olympics, I was on a family hiking holiday in Yorkshire in the north of England. And in the evenings, after a meal and a couple of drinks in the pub, we would sit down to watch coverage of the biggest sports. My favourite to watch? Track cycling.
If you’ve never watched a bunch of athletes, all of whom have thighs with larger circumferences than a supermodel’s waist, racing around a polished wooden track on bikes that only have one enormous gear, no freewheel, and no brakes, at ridiculous speeds, I can highly recommend it. It is a sport that the UK particularly excels at.
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We even have our own ‘golden couple’ of track cycling, Jason Kenny and Laura Trott, who were at the time engaged to be married. Sir Jason and Dame Laura Kenny, who were respectively knighted and damed (I made that word up) in 2022, have an unbelievable 12 Olympic gold medals between them.
On this particular evening of competition, Laura had already completed all of her events and she was cheering Jason on to winning his third and final Rio gold medal. As the crowd, and we in our small Yorkshire hotel room, roared Jason across the finish line, Laura tweeted: "Arghhhh!!!!!! I love him to bits! Our kids have to get some of these genes right?!"
Naturally, this piqued the interest of the geneticist in me. What actually are those odds? Will their future offspring be sporting superstars, or will they be watching the Paris 2024 Olympics on the sofa with the rest of us?
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Although an off-the-cuff comment, Laura has good reason to be very hopeful. The chances of her and Jason's combined genes producing children who are not only very athletic but potential Olympians are a lot higher than for the rest of us.
It's the same as fast bowler Stuart Broad having a better chance of becoming a star cricketer because his father Chris batted for England. Or British middleweight boxing champion Chris Eubank Jr being more likely to become a top boxer than his friends at school. Or long-distance runner Eilish McColgan thanking Olympic medallist mother Liz for her athleticism. Likewise, any Jason-Laura offspring (they have two children) will have a huge genetic head start.
However, while there are some human traits (such as those that control hair colour, lactose intolerance, and the ability to tan) that can be tracked down to single genes, this is clearly not the sole case for one’s possibility of becoming an Olympic athlete.
My own field of expertise is the genetics of body weight, where we know of the involvement of over a thousand genes. Consider some of the characteristics needed to be an elite cyclist. You'd need the right mix of ‘fast-twitch’ and ‘slow-twitch’ muscle fibres, great balance, high aerobic capacity, a fast recovery speed, a high pain threshold and the ability to focus – just to name a few.
One can only imagine the genetic complexity underlying the confluence of these multiple traits. With so many genes involved, it is currently impossible to make exact predictions about how talented Jason and Laura’s kids will be.
These complex traits always come down to an ideal combination of genes and environmental factors, plus a dash of plain luck.
Nature vs nurture
Being brought up in a household with two multiple gold medal-winning cyclists would have a powerful influence on their children. They will grow up in a highly competitive environment and are likely to be heavily involved in sports in their daily lives.
Similarly, the type of food that such children eat is going to be better than most. Two Olympians such as Laura and Jason, with nutritional advisers coming out of their ears, are unlikely to feed their children junk.
But however helpful or unhelpful your environment, you still need the right genes to flourish. That is why, across all areas of life, we see examples of dazzling genes passing down through generations – musical parents often breed musical children, and good looks pass from parent to child.
The question is how the child handles the genes they have been given. They can either use them to their advantage or not. To use the hand of poker analogy: you can have a good hand or a bad hand in terms of genes, and you can only blame your folks for that. But you can still win with a bad hand and still lose with a good one, depending on how you play the game.
So, nothing is certain, and there will come a day, perhaps in the next 20 years, when we will understand in detail how our genes make us fat or thin, or fast or slow, or govern how we look, perform or behave.
For now, though, it's safe to say that Jason and Laura’s children will have such a genetic and environmental head start that you probably wouldn't want your children lining up against them on sports day.
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