Africa’s evolution conundrum

How was Africa’s evolution  different from other continents from a human evolution perspective ?

Africa had a headstart when it came to human evolution.( mentioned one of the earliest hominin species – Lucy being in Ethiopia in my earliest posts )
Africa was the first continent to have evolved into Homo Sapiens – the “smarter” human species..which replaced the Neandrathals in Europe and Hominids in Asia .
Africans appear to have enjoyed geographically huge head starts over humans on other continents.  That makes Africa’s economic struggles today, compared with the successes of other continents, particularly puzzling.  It’s the opposite of what one would expect from the runner first off the block” ( Source : Jared Diamond – National Geographic 2005 )

But what made these Homo Sapiens expand into other continents like Europe , Asia etc .
Coupe of factors
a.) Agriculture  – Much of African landscape esp on the North consisted of jungle , swamps , desert, plateaus which were difficult to grow rice/ wheat /other crops of daily use. Infact on the contrary the vegetation did give Africa a head start in diseases/ epidemics…malaria/ yellow fever and other virulent diseases

b.) Beasts of burden – Africa’s wildlife – the rhinos, gazelles and the giraffes refused to be easy beasts of burden

c.) Rivers of trade – Most of Africa’s rivers also pose an issue as they are not navigable and hence restrict trade..While Europe , Asia had huge navigable rivers which facilitated trade and hence a common culture

Interesting to imagine how human evolution may have been different of any of these factors may have spanned differently in history or if the early African Homo Sapiens may have found a way around these .