How Global Interrelatedness had been demonstrated in Africia

I am writing a paper for my 20th Century World History class. I need some information on how Africa has demonstrated global interrelatedness. The areas of interest are colonialism 1800's to Post-conlonalism Era. Period should cover late 1800's, 1960 and 1990's. Plus please explain what is global interrelatedness and why it was late coming to Africia?