American Lindsey Van in action during the Nordic World Ski Championships. (Mike Hewitt/Getty Images)

David Epstein is the author of “The Sports Gene.”

The Russian men’s ski jump coach offered a chilly welcome to the athletes who will be competing in the debut of the women’s event at the Winter Olympics on Tuesday. “I’m not a fan of women’s ski jumping,” Alexander Arefyev told the newspaper Izvestia. “It’s a pretty difficult sport with a high risk of injury. If a man gets a serious injury, it’s still not fatal, but for women it could end much more seriously.” For good measure, Arefyev added: “Women have another purpose — to have children, to do housework, to create hearth and home.”

As jarring as that sounds in 2014, it is that sort of thinking about sex differences and athletic performance that helped keep women’s ski jump out of the Olympics until this year. If Arefyev could see past his prejudice, he might notice that female biology can be advantageous in his sport. The goal, after all, is to be an in­cred­ibly light projectile in a semi-permeable suit. Women can be endowed to fly as far as men, or in some cases farther. Ahead of the 2010 Winter Games, American Lindsey Van held the overall record for longest jump at the Vancouver Olympics site. She’ll be one of three U.S. women ski jumping in Sochi.

But this breakthrough moment shouldn’t herald the end of separate men’s and women’s events. Certainly, a shameful history of discrimination has hindered female athletes. Willfully ignoring sex differences, though, isn’t good for women’s sports, either.

The pseudoscientific ideas that blocked female ski jumpers for so long are similar to the ill-informed notions that put hurdles in front of women’s track. In the interest of protecting female runners from feared consequences such as infertility and premature aging, all women’s events longer than 200 meters were eliminated after the 1928 Amsterdam Summer Games. News reports described an awful scene at the finish of the women’s 800-meter race that year, with runners sprawled on the cinders in exhaustion. A New York Evening Post reporter wrote about “11 wretched women, 5 of whom dropped out before the finish, while 5 collapsed after reaching the tape.” A New York Times piece concluded: “This distance makes too great a call on feminine strength.”

Women’s and men’s world records in many events are separated by persistent gaps.

Except that’s not actually how the race went. As Running Times reported in 2012, none of the women dropped out, only one fell at the finish while leaning for the line — not unusual for men or women — and three others bested the previous world record. It’s hard to believe that the Evening Post scribe even attended the race, as there were only nine women competing.

The fallacies he promoted were stubbornly persistent. Women’s middle- and long-distance events were banned for 32 years. Not until 2008 did women have all the same events on the Olympic track as men. Before Kathrine Switzer became the first woman officially to finish the Boston Marathon in 1967, she was told that her uterus would collapse. It was only around the millennium that the guidelines for exercise during pregnancy flipped, and rather than something to be avoided it is now recommended. British marathoner Paula Radcliffe was celebrated for training well into her third trimester and then leading the 2007 New York City Marathon from gun to tape 10 months after giving birth.

In fact, as women were given opportunities to participate, they began gaining on men. In 1992, the journal Nature published a paper by two UCLA physiologists with the title: “Will women soon outrun men?” The physiologists graphed men’s and women’s running records through history and saw that the improvement in women’s times was far steeper. By extrapolating the curves into the future, the authors determined that women should beat men in all running events in the first half of the 21st century. “It is the rates of improvement that are so strikingly different,” they wrote. “The gap is progressively closing.”

In 2004, Nature featured another such paper: “Momentous sprint at the 2156 Olympics? ” — a reference to the projected date when women would outstrip men in the 100-meter dash. A paper the following year in the British Journal of Sports Medicine did away with the question mark and simply declared in its title, “Women will do it in the long run.” Could it be that male dominance of world records was all along an artifact of the discrimination that kept women from competing? Well, no.

The papers predicting that women would overtake men implied that the progression of women’s performance from the 1950s to the 1980s was part of a stable trajectory. In reality it was a momentary explosion followed by a plateau — a plateau that women, but not men, have reached. In terms of top speed in a range of running events, women began leveling off by the 1980s, and their records stagnated after the crackdown on mega-doping of female athletes from some Eastern Bloc nations. The numbers are now unequivocal: Elite women are not catching elite men nor maintaining their position. Men are ever so slightly pulling away.

From the 100 meters to the 10,000 meters, the gap between elite male and female performers generally stands around 11 percent. At the pro level, that’s a chasm. The women’s 100 record would have been too slow by a quarter-second to qualify for entry into the men’s field at the 2012 Olympics. In the 10,000 meters, the women’s world-record performance would be lapped by a man who made the minimum Olympic qualifying standard. Larger gaps occur in throwing and pure explosion events. In the long jump, women are 19 percent behind men. The gap in distance swimming races is smaller — 6 percent in the 800-meter freestyle.

Thanks in large part to testosterone, men are generally heavier and taller than women. They have longer limbs relative to their height, bigger hearts and lungs, less fat, denser bones, more oxygen-carrying red blood cells, heavier skeletons that support more muscle — 80 percent more in the upper body, on average, which is about the difference between male and female gorillas — and narrower hips that make for more efficient running and decrease the chance of injury. But since these differences generally don’t appear until puberty, boys’ and girls’ records in track tend to be identical before age 10. There’s scant biological reason to separate young boys and girls in competitions.

In 2011, the NCAA, after consultation with scientific experts and bodies like the National Center for Lesbian Rights, determined that male-to-female transgender athletes should sit out a year while undergoing testosterone-suppression treatment before competing on women’s teams. That guideline fits well with the experiences of transgender athletes such as Joanna Harper, a 57-year-old medical physicist and 2012 U.S. national cross-country champion for the 55-to-59 age group.

Harper was born male but started hormone therapy in August 2004 to suppress her body’s testosterone and physically transition to female. Like any good scientist, she recorded data, and she found herself getting slower by the end of the first month. “I felt the same when I ran,” she says. “I just couldn’t go as fast.”

Harper’s time in the Helvetia Half Marathon in Portland, Ore., was about 50 seconds per mile slower in 2005 than it was in 2003, just before the transition. But age- and sex-graded performance standards indicate that Harper is precisely as competitive now as a female as she was as a male. And data she has for a half-dozen other athletes with similar histories follow the same pattern.

Given the history of discrimination, it is easy to understand why some supporters of women’s athletics might feel the urge to deny the male advantage in many sports. But it can be taken to ridiculous extremes.

In the 2007 book “Playing With the Boys,” for instance, Eileen McDonagh and Laura Pappano wield a misleading statistical argument in an attempt to show that women are faster than men and that there should be no sex separation. The authors analyze the times of the top 207 finishers from the 2003 Boston Marathon and find that the women in that group finished several minutes faster on average than the men. Of course, that is because the race unfolds like this: The pro men finish; 15 minutes later, the pro women finish; then a stream of people, mostly amateur men, finish. So the authors are really slicing the data so as to compare pro women to pro men diluted by amateur men. A more telling stat would have been simply to say that only 16 women finished in the top 207 runners, and the 16th woman was more than 20 minutes behind the 16th man.

As Alice Dreger, professor of clinical medical humanities and bioethics in the Feinberg School of Medicine at Northwestern University, told me: “The reason we have females separated in sports is because in many sports, the best female athletes can’t compete with the best male athletes. And everybody knows that, but nobody wants to say it. Females are structured like a disabled class for all sorts of, I think, good reasons.”

If we wanted simply to see the fastest runners, we could have cheetahs race instead of humans. But sports are the ultimate contrivances: Take agreed-upon rules, add meaning. We must be vigilant to ensure that all women who want to compete have the opportunity to do so, but the idea that women’s athletic performances must be equivalent to men’s in order to be deemed remarkable belittles the achievements of female competitors.

Similarly, in instances when women do equally well or better than men, as can happen in ski jump, it should come as no affront to male athletes. Biology may help explain those times, those distances, those records. In long-distance swimming, for instance, the performance gap between men and women closes, particularly when the water is very cold, perhaps because women’s higher percentage of body fat becomes advantageous.

As the Russian coach’s comments show, though, men who grew up believing that they have a monopoly on biological advantages in sports may have trouble accepting female athletes’ success. Whitney Childers, spokeswoman for the U.S. women’s ski jump team, says that some of the resistance to women competing had to do with the idea, especially in Northern Europe, that women “would diminish the masculinity of the sport.”

That idea is silly, and it was never the point of the fight for inclusion of women’s ski jump in the Olympics. “The women are super stoked for their male [ski jumping] friends,” Childers says. “They don’t want to compare themselves, they just wanted their own competition. They just want to show that they’re devoted and are not these fragile little creatures.”

Come Tuesday, if not for the announcers, you won’t be able to tell if those are men or women with their skis splayed, flying through the air. All you’ll see are athletes.

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