Sibling rivalry is a fierce thing, but it seems like more often than not, athletic talent isn’t limited to just one star son (or daughter). Case study: Devin, Danielle, and Dustin Wahl attempted to make history on July 27 by becoming the first brother-and-sister trio to successfully swim the English Channel (and raise a bunch of money for the Alzheimer's Association while they were at it). Dustin was sidelined by cramps and sickness, leaving his brother and sister to complete the swim—not a history-making finish, but still impressive in its own right.
The Wahls certainly have genetics in their favor, as their mom and dad were both endurance athletes in their heyday. But their quest raises an interesting question: Are parents likely to pass on their athletic ability to all of their children equally, or is natural talent essentially a hereditary crapshoot?
Probably a bit of both, says Dr. Steve Roth, associate professor of kinesiology and director of the Functional Genomics Laboratory at the University of Maryland. Understanding shared family talent comes down to good old nature and nurture. First, there are the physical traits: "Siblings share a significant amount of the genetic variation they get from their parents, so if those parents have traits that lend themselves to certain performance characteristics, then a group of siblings will be more likely to carry those and share those, than say, three or four random people," Roth says.
But siblings can also inherit few of the same traits and still turn out similar in big ways. Consider the Williams sisters, says Roth: "They have very different physiques, but they've both managed to excel at tennis despite their physical differences."
Which leads to the other part of it: physical characteristics aren't the only advantages kids can inherit from their parents. "Being an elite athlete requires motivation, focus, competitiveness—all of which have genetic components as well, and can very likely be passed on to some or all of one's children."
The fact that the Wahl kids have two athletic parents certainly increases the chances of inheriting advantageous genes, says Roth, both physically and psychologically. But more importantly, it has shaped the environment they grew up in.
"They probably watched their parents train and were involved earlier in sports because of their parents' lifestyle," he says. In fact, Roth says we often don't give the latter side of the nature-versus-nurture argument the credit it deserves. "I'd say that genes are less important than environment, if I had to put money on it—and that's coming from someone who's made a career out of studying genetics."
Research backs this up, too: While scientists have found more than 200 genes that seem to be related to athletic ability, most admit that these components only tell part of the story. As a 2012 review published in the British Journal of Sports Medicine puts it, "Individual performance thresholds are determined by our genetic make-up, and training can be defined as the process by which genetic potential is realized."
As far as the Wahl siblings go, their genetic potential certainly seems to have been realized—English Channel record or no. The oldest of the three, Devin, has completed two Ironmans, and middle-sibling Danielle already conquered the channel last year, the fastest American to do so in 2013.
Youngest brother Dustin, just 19, had been training five hours a day to prepare. He may have science on his side, as well: Studies have shown that younger-born children report less sports-related performance anxiety, take more risks, and are more likely to become elite athletes.
Bottom line: There's a good chance that athletic siblings share at least some natural talent—but more importantly, they've shared an environment and support system that's fostered their true ability. Consider that next time you’re around your siblings and feel that old competitive urge rearing its head.