I spent some time living and working in Kenya's Western Rift Valley. The school I worked at was at an altitude of 2000m+ and the locals claimed that their tribe had at one time or another held every long distance running record in World Athletics.
I used to train the school football team in the evenings and I would often get to the playing fields a little early to chat with the students and also to warm up with the runners. I was a decent middle-distance runner at school - 1500m was my best event so I enjoyed running with these guys. However, I could only keep up for 2 laps! After 1 lap I thought - these guys are gonna get tired soon. After 2 laps I thought I better quit while i'm still alive. It was like watching the Duracell Bunny advert, my batteries ran out quickly but they just kept going and going and going and going.
For a lot of the locals, athletics represents one of their best chances to escape a life of poverty. That part of Kenya is a beautiful place, with amazing people and wonderful athletes but unfortunately, it is very poor.
Edit - If you look at the photos you've used, those athletes with the prefix "Kip" on their name are likely members of a tribe from the Kalenjin group who inhabit the area of Kenya I was in
RE: See The Reason Why Kenyans Are Dominant In Marathons