We write on behalf of the Chinese Biological Investigators Society, a professional organization of overseas and native Chinese scientists (www.cbisociety.org), to express our concern over your online News 'Explainer' about the performance of Ye Shiwen, a 16-year-old Chinese swimmer who won gold medals in the 200- and 400-metre individual medley during the London 2012 Olympics (http://doi.org/h55; 2012). We feel strongly that you overlooked some important facts.

You join in the widespread speculation that Ye's performance was anomalous, in which it has generally been implied that no one else has accomplished such a feat before without the aid of performance-enhancing drugs — a premise that, in our view, stems from data cherry-picked to support an unfounded accusation.

You indicate that Ye's 400-metre performance was about 7 seconds faster than a time she set at a major meet a year earlier. Ye's personal best was actually set in 2010, when she was 14 years old. She improved her performance at the Olympics final by 5s over her earlier personal best — a feat that is not anomalous, but is expected for elite swimmers of Ye's age as they grow bigger and stronger.

Credit: COURTESY GUANGBO CHEN, STO WERS INST. FOR MED. RES.

There are many examples of elite swimmers who showed a significant improvement at a young age. For example, Australian swimmer Ian Thorpe took 5s off his 400-metre freestyle time between the ages of 15 and 16, and UK swimmer Adrian Moorhouse, Seoul Olympics gold medallist in 1988, improved by 4s in the 200-metre breaststroke aged 17. The same happened to the other seven finalists in the 2012 Olympics women's 400-metre medley (see 'Young swimmers' improvements'). Also, Rūta Meilutytė, a 15-year-old Lithuanian swimmer, improved her personal best by more than 4% in the 100-metre breaststroke, compared with Ye's improvement of 2% in the 400-metre medley.

You say that Ye “raised eyebrows” by her showing in the last 50 metres of the race, noting that she swam faster than US swimmer Ryan Lochte when he won gold in the men's 400-metre medley, the second-fastest time ever for that event. What you do not mention is that Ye was actually more than 23s slower over 400metres than Lochte, an eternity for elite swimmers at this distance.

In fact, the time for Lochte's last 50 metres is nowhere near the second-fastest ever for that event: several other swimmers in the same men's final were faster than he was and faster than Ye. Lochte ranked only fifth in the last 50 metres, at 29.1s, which was significantly slower than Japan's Yuya Horihata (27.87s) and three other swimmers competing in the same event. Ye's time was 28.93s.

All of this information is available on the Internet. It is unfortunate that Nature seems to have put a stamp of scientific approval on the Western media's unsubstantiated speculation that Ye's feat is humanly impossible without the aid of performance-enhancing drugs.

We emphasize that our data serve only to provide a more complete backdrop to Ye's achievement, and not to negate her spectacular performance in winning two golds and shattering the world record.