Nature or nurture?

How important is the body you were born with, when it comes to sports excellence? Is it crucial? Or is it just one factor in a big bag of factors?

The successes at the Rio 2016 Olympics tonight of American gymnast Simone Biles and American swimmer Michael Phelps, each of whom reinforced their ranking among the greatest their sport has seen, has reopened the debate about how important body shape is. That is, nature.

As opposed to training and coaching. Which is nurture.

For one of these athletes, the conversation about “the perfect body” has been going on for a decade.

Phelps has been the subject of “freakish body perfect for swimming” stories since before Beijing 2008, at the latest.

Here is one of them.

In short, the evidence cited claims Phelps has unusually long arms, unusually short legs, a long torso and particularly flexible ankles, all of which is advantageous for the sport of swimming.

However, the magazine Scientific American which, as the title suggests is not produced by sports journalists, in 2008 did a Q&A with a sports medicine practitioner who rebuts pretty much the whole of the “Phelps’s weird body makes the difference” stuff.

Which brings us to Simone Biles, the 4-foot-8 gymnast who led the U.S. women’s team to the gold medal.

She clearly is in prime condition and has devoted her life to excelling in her sport, like Phelps. But …

She is remarkably short even in a sport which seems populated by shorter-than-average people. (In women’s gym, the tall one in the group photo is 5-foot-2.)

It would seem that being short is helpful in standing out in the sport.

The New York Times recently did a multimedia piece that seems to suggest that Biles’s signature (and eponymous) floor-exercise move, a “double layout with a blind twist and a blind landing” is helped by Biles being 4-foot-8. Her ability to be at top speed very quickly gives her a “longer pass” in her tumbling runs — long enough to finish off her famous move.

But, getting back to Scientific American, though certain sports seem to favor certain bodies — hello, basketball — an exception can nearly always be found. The short swimmer with a gold medal. The average-sized gymnast. A tall sprinter.

Thus, perhaps as specific as we can be about this is … a body type may give an athlete a boost, but the rest of it is up to training and coaching and mental toughness and maybe luck … and all the other factors that produce champions.