The winners of Monday's Boston Marathon are in, and Ethiopians for the first time ever swept the men's and women's races, taking five of the six winning spots in a race that had been dominated by Kenyans for decades.
Lemi Berhanu Hayle won the men's race in 2 hours, 12 minutes, and 45 seconds, beating out defending champion Lelisa Desisa by 47 seconds. Yemane Adhane Tsegay came in third, 30 seconds behind Mr. Desisa, to round out the men's top three spots dominated by his countrymen.
Atsede Baysa, two-time Chicago Marathon champion, won the women's race in 2 hours 29 minutes, and 19 seconds, 44 seconds ahead of fellow Ethiopian Tirfi Tsegaye. Joyce Chepkirui, the only Kenyan to receive a medal this year, came in 47 seconds after Ms. Tsegaye.
Whether it's Ethiopians or Kenyans who dominate the top ranks of the world's most competitive marathons, both east African countries are running powerhouses.
The world's best runners come from three mountainous districts near the Rift Valley in Africa, according to the BBC: Nandi in Kenya and Arsi and Shewa in Ethiopia.
Out of 149 male marathon performances faster than 2 hour and 10 minutes in 2013, 80 were by Kenyans, 47 by Ethiopians, and eight by Eritreans and Ugandans, who are from the same region and of similar ethnicity, as Runner's World reports.
Of the 300 best men runners in the world in 2014, 246 were east African. While the women's ratios are less extreme, they are becoming more so every year, reports the running magazine.
What makes people from this region exceptional runners is a question that many are trying to answer.
Some people suggest that because East African runners train at high altitudes, they have increased red blood cells which helps them excel at endurance sports. But as Ben Oakley, head of Childhood, Youth and Sport at Open University in Milton Keynes, England, and a former Olympic coach, points out to the BBC, this doesn't explain why there aren't more great runners from the Mexican Andes and from large parts of central Asia.
"My reading suggests the efficiency of an east African runner's light and lean body could be a significant factor," wrote Mr. Oakley.
Some studies have shown that East African runners use less energy compared to Caucasian ones. One reason for this might be that they carry a few less grams on the feet and ankles, wrote Oakley, a feature of the most common body shape in East Africa, which means these runners require less energy to keep a fast pace.
But this is mostly informed speculation; nobody knows for sure.
"Of these explanations the influence of biology is hotly debated, but overall the work ethic needed to succeed at the top level takes place in a social and economic milieu that, for me, is a major influence,” Oakley wrote.
Monday's Boston marathon results come as the World Anti-Doping Agency put Kenya on probation after more than 40 athletes tested positive for performance-enhancing drugs since the 2012 Olympics. Earlier this year, the general secretary of Ethiopia's anti-doping agency said that nine runners from that country, five of them "top athletes," were under investigation for doping. There have been major doping scandals among Russian runners, as well, dealing blows to a sport in the buildup to the Olympics in Rio de Janeiro in August, as USA Today reported.
With their focus on qualifying for the Olympics in Rio, most of the top American runners, including 2014 winner Meb Keflezighi (who is Eritrean-born), sat the Boston Marathon out after running in the US Olympic trials in February.
This report uses material from the Associated Press.