I've lived in East Asia for the past 35 years, and competed internationally out here (and elsewhere) for the 8-10 of those years that corresponded to my post-university-but-working-a-day-job prime). I first competed in China in 1991, when the country was fantastically poor. It was a fantastic experience. In my events (800-5000) most of the competitive athletes came from the hardscrabble northeast and northwest. Windburned farmers who knew how to "eat bitter". Few spoke Mandarin (the linguistic diversity of China roughly corresponds to the linguistic diversity of Europe). For the most part, athletic performance tracks to economics. But also, as someone noted, they don't run imperial distances in China (or anywhere outside of the U.S. and U.K.). That said, I ran 1500 in track meets in China back in the 90s at the time the men's national record was in the low 3:40s. At that time there was 1-2 guys in the entire 1.4 billion country who could beat me. Mind-blowing. China was at the beginning of its long and astonishing emergence from the Cultural Revolution and Great Leap Forward and other economic catastrophes, and there was no culture at all of running or exercise. If I went for a training run, locals would stop and stare at me like I had landed from another planet. Today there are hundreds of road races in China and tens of millions of "hobby joggers" who pursue and enjoy fitness activities. That said, the running/sports culture is still very new there. Chinese women's running success can be attributed to doping, as everyone knows but World Athletics refuses to acknowledge. Ma's Army athletes have admitted it, and other proof has been tabled. Doping in the 90s disproportionally benefited women, and that's the reason the Chinese women have always been better than the men. Chinese Olympic success can be attributed to a very intentional targeting of "soft" sports/medals. Olympic success is political success. Google "Project 119" to see the sports they (very successfully) identified as good opportunities. If you are looking for real-world Chinese sporting success, check the table tennis teams of the top 20 table tennis-playing nations. It's the Chinese A team, B team, C team, etc. Japan is maybe the only exception, hahaha. As for DNA and body type, as one poster noted, Chinese come in all shapes and sizes (Yao Ming the obvious example). In my view, running (and sporting) success is economics (society-wide health), then desire (and role models). As another posted noted, there are still hundreds of millions of Chinese scratching out an existence, despite the enormous leaps the country has taken over the past 40 years.