This tells the tale.
Ethiopian Women are above their competition. Notice that every (top)contender on this race either achieved Personal Best (PB) or National Record (NR) when racing against the Ethiopian women.
Pos Bib Athlete Country Mark
1 204 Dibaba Tirunesh ETH 14:38.59 (CR)
2 202 Defar Meseret ETH 14:39.54
3 203 Dibaba Ejegayehu ETH 14:42.47
4 210 Melkamu Meselech ETH 14:43.47
The rest:
5 120 Xing Huina CHN 14:43.64 (PB)
6 722 Mohamed Zakia Mrisho TAN 14:43.87(NR)
7 457 Ngetich Prisca Jepleting KEN 14:44.00 (PB)
8 458 Ochichi Isabella KEN 14:45.14(PB)
9 664 Shobukhova Liliya RUS 14:47.07(PB)
10 53 Kravtsova Olga BLR 14:47.75 (NR)
11 117 Sun Yingjie CHN 14:51.19 (SB)