This is why I asked if these 'experts' knew how many countries there were in east Africa. To me there's east Africa(Kenya, Tanzania, Uganda...sometimes Egypt and Sudan but those are mostly considered North Africa by alot of people.) and the horn(Eritrea, Ethiopia, Somalia, and Djbouti).
I disagree with that one. I noticed that south Sudanese(nilotic people) (not all) are more lanky in built. You have very thin people in the North, but many also are generally more husky or has similar built at times as rugby players. As far as body building goes, i noticed men in the North along with Egyptians usually developed well defined physique quite easily.
Egyptians
South Sudanese Rugby player based in Australia.
Sudanese Rugby player. Notice how much thicker body wise than the southern counterparts.
Both play the same sport, but obviously different body type. Then again you can find different body types in all groups, but what is basically comes down to genetic. For example many women in the North both Nile Valley Northern Sudan and Upper Egyptians, are more shapely bodywise than our southern counter parts that are usually very thin, talk, and lanky. Which make them suited for models in the western world.
, yet between 18-27 they were 
