The Masai didn't have atherosclerosis on traditional diet

[invisible]

http://www.cholesterol-and-health.com/Did-Masai-Have-Atherosclerosis.html

Summary: The smaller sample of Masai in an isolated region shows no atherosclerosis. Broader study with large sample size (covering larger geographical area) did, however many of the Masai in that often cited study had flour and sugar in their diet.

[TylerDurden]

The article admits to heavy speculation without any real evidence. Also, grains seem to have always been a small  part of the Masai diet, not just appearing in 1950s onwards.