Source: David Eltis and David Richardson, Atlas of the Transatlantic Slave Trade

Before the advent of DNA testing, scholars relied on shipping records that listed the African ports from which slaves were exported to determine where in Africa the African-descended population of the United States originated. But these lists were quite limited because they noted only the port of departure and not the actual community from which the enslaved were taken. 

Advancements in DNA analyses, along with African shipping records, have revealed that African Americans do not have roots in the entire continent. A relatively small number of African groups supplied the lion's share of the ancestral African population.

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In fact, three large regions of Atlantic Africa were the major contributors to the slave trade: Upper Guinea, including the modern countries of Senegal, Mali, Gambia, Guinea, Sierra Leone and Liberia; Lower Guinea, including the southern portions of Eastern Ivory Coast, Ghana, Togo, Benin and Nigeria; and West Central Africa, which encompassed mostly the western portions of the Democratic Republic of Congo and Angola. In all, these regions made up only about 15 percent of Africa's total area, all on the Atlantic side of the continent.

People were once skeptical of claims made by early DNA ancestry-tracing services that they could identify a subject's "tribe" or "ethnicity" in Africa; the available data didn't seem to sustain such claims. But new ways of calculating ancestry from the genome and larger African samples can make determining ethnic identifications more accurate.

The Language Connection

Today, speaking a common language is the primary way to identify an African tribal or ethnic affiliation. Since African languages are quite stable and reports of these languages demonstrate that there has not been any large population movement within the slave-exporting region of Africa in the past 400 years or so, it should be relatively easy to match modern ethnicities or tribes with those of the slave-trade era. However, the names of these languages and ethnic groups have changed over that period. For example, in 1767 a German missionary named Christian Georg Andreas Oldendorp did a survey of slaves living in the Danish West Indies to try to determine which languages should be used for evangelical purposes. The Danish West Indies received slaves from the same shipping route that North America used.

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Oldendorp, calculating ethnicity by language, listed 30 apparently different languages (his terminology sometimes makes it unclear where political and where linguistic units divided), and he provided vocabulary for 26 of these languages, which allows us to be certain of the modern equivalent. 

In the Americas, Africans were most likely to form social units with other people who spoke their language, even if they might belong to different political units; in Africa their identity was more likely connected to a political unit. Their rulers collected taxes, demanded service (including the military service that resulted in their enslavement) and rendered justice, while neighboring polities might well be hostile even if they spoke the same language.

People collecting information about identity in America were likely to choose linguistic units, while those commenting on it in Africa were more likely to focus on political units. This created an interesting paradox: The names of African "nations" in America often did not match exactly with the names of "nations" in Africa.

For African Americans seeking to learn about their African ancestry, there is also the issue of ethnic associations. Since the inception of colonialism, Africans have come more and more often to cast their identity in terms of ethnicity, or by "tribal" identity. While most certainly do recognize themselves as citizens of Senegal, Ghana or Angola, they are also quite likely to recognize identity as Wolof, Akan or Mbundu.

Neither the political units nor, as often as not, the linguistic units are directly comparable to designations of nations or states given for the era of the slave trade. In fact, less than one-third of Oldendorp's language names are the current names for the language. Ethnic maps, like the famous map published by George Peter Murdock in 1959, are the basis for most understandings of today's ethnicity, and researchers collecting DNA samples are likely to ask for these names when collecting the sample and report their results using the same names.

African Americans seeking their roots must understand that there was no Senegal or Ghana in the era of the slave trade, and that while Angola and Congo were commonly used as ethnic names, these places did not have anything like their modern borders. The names of some of the ethnic groups of today have changed, and anyone attempting to find the links to African ancestors must know something about the history of the group.

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According to Murdock's ethnic map, Africa has more than 1,000 ethnic groups and as many languages. By Oldendorp's definition, barely 30 of the ethnic groups on Murdock's map contributed to the population of the Americas. Africa appears to be somewhat less diverse in the era of the slave trade.

But using the geographic information that Oldendorp supplied, and plotting the borders and ethnicity according to the Murdock map, it becomes clear that Oldendorp's 30 ethnic groups encompassed 46 of today's ethnic groups. (This is because some modern ethnic groups make up two or three of Oldendorp's.) For a list of ethnic groups and their location in modern Africa, go to The Root article African Ethnicities and Their Origins.

For people seeking their roots, it is probably not as important to link to a long-lost political group or try to locate the 18th-century name of genetic ancestors. The real contribution of the results provided by DNA is that they connect an African American living in, say, Boston or New Orleans with an African who identifies himself by a name — say, Asante or Wolof — and who lives in Ghana or Senegal. The African American who shares genetic sequences with that person can link himself to that modern ethnic group. By matching genetic anomalies in an African American and an African, one can establish that these two individuals had common ancestors two centuries ago.

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Slavery and Jim Crow were meant to wrench African Americans from their African past, but with research and advances in science, the search for ties to a vast continent has narrowed considerably.

Linda Heywood is a professor of history and the director of African-American studies at Boston University. John Thornton is a professor of history and African-American studies at Boston University.