The morning after the night before there was only one name on everybody's lips. It was not Ryan Lochte or Michael Phelps. In fact it was exactly the same person those two had been talking about themselves: Ye Shiwen. The 16-year-old, born and raised in Hangzhou out on the east coast of China, became the first swimmer to break a world record at these Olympics when she knocked more than a second off the time that won Steph Rice gold back in Beijing in 2008. And Rice had the advantage of swimming in a polyurethane suit, of the kind long since banned by the sport's governing body, Fina. It was not just Ye's speed, or her age, that was so staggering – it was the manner of her victory.

After 300m of fly, back and breaststroke, Ye was eight-tenths of a second behind USA's world champion, Elizabeth Beisel. And then, with 100m to go, something extraordinary happened. She swam her first 50m of freestyle in 29.25sec, and her second in 28.93. Those are just numbers, and mean little to those who do not study the sport. To put them in context, consider this: Ye was faster in the final 50m of her own 400m IM than Lochte was in his.

"Yeah, we were talking about that at dinner," Lochte said. "It is pretty impressive. She's fast. If she was there with me, she might have beat me." There's no might about it. Ye was 0.17 quicker over the final 50m of freestyle than the man many reckon to be the greatest all-round swimmer in the world. Beisel, Lochte's training partner, had no chance. She was two seconds slower over the final 50m.

It is the first time in history such a thing has happened. But it will not be the last. Ominously, Ye is certain she can get better still, and seeing as she is only 16, who can doubt her? "There's much room for improvement," she said. "It's true for breaststroke I am lagging behind but I think my freestyle result is also not that good. Usually I'm very bad at turning. This is one of my worst basic skills, but turning is a very important skill, therefore I was practising my turns before the competition." She says she is even better at the 200m IM, the event in which she won gold at the world championships in Shanghai last year, when she was 15.

Ye's team-mate Li Xuanxu took bronze and she is only 17 herself. She too came home in under 30 seconds, with a time of 29.77. The next best split was almost a second slower.

Then there was Sun Yang, 20, and also from Hangzhou. The world knew a little more about him, after he beat the longest-standing record in swimming at the world championships last year, taking 0.42 off the 1500m time set by the great Grant Hackett back in 2001.

Sun won the 800m in Shanghai, too. In London he has already won gold and set a new Olympic record in the 400m freestyle, beating South Korea's world and Olympic champion Park Tae-hwan. And on Sunday morning he was the fastest-qualifier in the heats of the 200m freestyle, pipping Lochte. It is entirely possible that Sun will sweep all the freestyle distances from 200m to 1500m.

China's success has prompted, with tedious predictability, dark mutterings about exactly how they are achieving it. Over the course of the 1990s they had 40 swimmers banned after positive doping tests. The sceptics – or perhaps cynics – would say that the doubts about Ye, Li and Sun are the inevitable consequence of that history.

There is, of course, no evidence to support such thoughts other than the talent and speed of the athletes themselves. Surely the success of this young generation stems from a legacy of a very different kind – that of the Beijing Olympics. China has sent 49 swimmers to these Games, and 27 of them were born after 1990. On the women's side, there are eight who were born in 1995 or after. The country's success in the Aquatics Centre surely owes a lot to the investment in the sport made before the 2008 Games.

Their medals could also owe something to the unique talent identification system China uses to stream children into different sports. In his excellent 2003 profile of Yao Ming for the New Yorker, Pete Hessler, talks about how Chinese basketball players are selected strictly on the basis of their height and genealogy. "We go to the schools and look at the children's height, and then we check their parents' height," Hessler was told by one high school coach. "The method of early recruitment is a product of China's inability to provide every public school with coaches and sports facilities," Hessler wrote. "The system has proved effective in low-participation, routine-based sports like gymnastics and diving." And also, it seems, swimming.

Ye says she started swimming in 2003 because her "teacher spotted she had big hands". In swimming, where physique determines so much, the rather-rudimentary method of recruiting young athletes on the basis of their physical characteristics rather than their talent or inclination for the sport, appears to work well. It is coupled, of course, to an infamously fierce training programme, to the point where Ye was asked whether she resented being treated like a robot. "Of course not," she replied. "I think we have very good training, very scientific-based training, that's why we all have progressed."