above map from trans-atlantic slavetrade database
The African Diaspora was the movement of Africans and their descendants from their homeland to places throughout the world - predominantly to the Americas, then later to Europe, the Middle East and other places around the globe. However there was a much earlier migration of families out of Africa that impacts the entire human family even today.
The term "Diaspora" is applied in particular to the descendents of the Black Africans who were enslaved and shipped to the Americas by way of the Atlantic slave trade, with the largest population in Brazil. People of Sub-Saharan descent number at least 800 million in Africa and over 140 million in the Western Hemisphere, representing around 14% of the world's population.
Based on human genetics, it is widely believed that prehistoric Africans who left the continent within the past 100,000 years are the ancestors of all non-African humans. But as communities began to form, especially in Egypt and the Middle East, these migrations were greatly reduced because the only land route out of the African continent is through the Sinai Peninsula. After the rise of civilization and the development of sailing, black Africans traveled to the Middle East, Europe, and Asia in a number of occupations. Many of these individuals settled in Europe and Asia and invariably intermarried with the local populations. Today, human genetic research suggests that mitochondrial DNA and Y chromosome haplotypes in Europeans and Asians have distant African ancestry. But these early migrations out of Africa are dwarfed by those associated with the Atlantic and Arab slave trades.