Gullah Geechee, Progenitors for African North American Maternal Lineage

¹Pennington Biomedical Research Center
²Fayetteville State University, Fayetteville North Carolina

^*Corresponding author: Jennifer Caldwell, Pennington Biomedical Research Center

Table 1: Overall HVS1 mtDNA Gullah Geechee and Africa Americans Frequencies.

Gullah Geechee as Progenitors for North Americans

Our theory uses the Trans-Atlantic Slave Trade as the bottleneck for filtering New World Africans and creating our modern African American gene pool. During the TAST millions of Africans were taken from numerous African Kingdoms and ethnic groups as prisoners of war. They were bought and bartered for war and luxurious materials like umbrellas, spices, and gunpowder. Many were brought from the inland parts of Africa to the West Coast to board slave ships headed to the Americas. Other enslaved Africans were taken north to Europe and millions to the Middle East. These migration patterns create a strong rationale to continue exploring the African Diaspora and reconstruct the histories of modern African people as they influence and diversify new lands [8].

Our aim in this article is to use the same datasets from [4]. and highlight the relationship between Gullah Geechee participants to their potential African American descendants; propose mechanisms that support the prevalence of cardiovascular disease seen in African North Americans. In a previous paper [9], we hypothesized Gullah Geechee as a progenitor population for North American Legacy Africans, specifically for those whose ancestors were forced into the Trans-Atlantic Slave Trade. The maternal lineage(mtDNA) is our focus for this research. From 1525 to 1856, approximately 132,000 enslaved women and girls were brought to continental North America directly from Africa or from the Caribbean. It is estimated that 66,000 of those women and girls survived reproductive age and bore children. Considering migrations, women who were breeders on plantations, and women who were separated from their families and forced to bear children at their new plantations, the maternal ancestors of today’s 40 million Legacy African Americans are relatively small. We recognize that some Legacy African Americans stem from European, North American, and Native American maternal lineages Amerindian lineage. However, this research focuses on the African maternal line of Legacy African Americans as we attempt to reconstruct their ancestry. 

Migrations influence Admixture of Legacy African Americans 

First middle passage

Unlike most ethnic groups, reconstructing the heritage of Legacy African Americans is complex. When researching African North Americans, we understand that 9 million Africans made it to continental North America while many lost their lives at sea, were thrown overboard for insurance claims as they were only spoiled property, succumbed to plagues and infections in the Americas, or did not live long enough to bear children. Historical records indicate that many enslaved African were given new names either on the slave ships or after being sold into slavery. Their surname was often discarded or seen as remnants of a “savage” past, deemed inappropriate which had no place in the Americas and were removed to further disconnect Africans from their heritage. While the First Middle Passage set the stage for Legacy African American ancestry, the Second Middle Passage shuffled the ancestral lineages of African Americans once again [2,9].

Second middle passage

Contrary to many other countries with enslaved populations, the United States North African population grew exponentially. In some cities, the African American population outsized the European population 3:1 [2]. This feat was a part of the imperialist expansion and capitalistic nature of slavery. African men and women were often breeders for plantation owners. While some enslaved Africans bore children for enslavers, others' sole job on the plantation was to breed the next generation, often with one or more partners. Plantations became familial centers as much as economic factories. Enslaved Africans were sometimes genetic family members of enslavers but also could be bought or given to extended family members, continuing the trend and connection.  Mating and reproduction often resulted from proximity; as a result, some Legacy African Americans’ heritage parallels with plantation families where they worked.

The Domestic Slave trade was the largest intercontinental slave trade of United States history and began after the rise of King Cotton in 1793. The invention of the cotton gin and the westward expansion following the Louisiana Purchase led to the Second Middle Passage. During this expansion, droves of enslaved Africans were chained and migrated from the Upper South (Maryland, Virginia, Tennessee, and North Carolina) to the Lower South (Georgia, South Carolina, Alabama, Mississippi, Louisiana, Florida, Arkansas, and Texas) to attend the workload [10]. This forced migration disrupted the family structure, with over 1 million African Americans being relocated to the South. The family structure and thus their genetic composition was admixed once again, causing more evolutionary homogeneity over time [11,12]. Husbands and wives, children and parents, and siblings alike were dismembered from the unity they came to know. Similar to the standards of the TAST, the Second Middle Passage (SMP) called for a separation of unity, families, and communities even after they reached their new southern destination. The consequences of subsequent alienation, relocation, and separation were compounded through the Civil War and Reconstruction. One element of African American culture is seen in the uprooting of families, imprinted in their gene flow, time and time again. 

Reconstruction and the African American Great Migration 

After the Civil War, many African Americans went on a quest to reunite with their families. Some remained on the plantations where they had been enslaved, becoming sharecroppers, while others had dreams of leaving the South for the “promised land” of advancement in northern states. Legacy African Americans were living in brutal and inhumane working conditions in the south, overt racism, “Black Codes” justice, and reinstatement of covert institutionalized slavery via the 13th Amendment and the “chain gang,” which left their lives vulnerable at the hand of their oppressors. The idea of the North became laws of the South, it was a way o, it was a way out of the debt system of sharecropping, and the promise of a new, autonomous life.  While the Second Middle Passage was the largest forced exodus of people in the United States, the period of American reconstruction, along with the 1st and 2^nd2nd Great Migrations, significantly shaped the demography, redistribution, and social structure of Legacy African Americans and modern Americans indirectly, as the largest internal migration of the United 2003). Migration is not only an evolutionary process of human diversity but also a social influencer of biological processes like reproduction, morbidity, and mortality. Early population records show that 90% of Legacy African American (LAA) populations live almost exclusively in southern states with South Carolina, Louisiana, and Mississippi as the most heavily populated. While half of the Legacy African American population remained in the south from 1890 onward, approximately 6 million LAA’s moved Northeast, North, and West to more urban environments. As we reconstruct the ancestral lineage of Legacy African American (LAAs), it is important to note that migration often occurred in familial patterns, frequently following the railroad tracks. Few went by cars, some by foot, and even in the secret of the night as the threat of escapees being lynched was common practice [13].

With the aid of contemporary media primarily from black-owned newspapers like the Chicago Defender, Pittsburg Courier, and California Eagle, communication about jobs, housing, and the luxuries of northern life spread throughout the south. Previous research notes the importance of the railroad system in Great Migration. Pullman porters often delivered newspapers from the north to southern rural areas [14]. Not only did people follow the closest railroad tracks to the urban cities in the north, but many migrants also used the trains legally and in secret to go north. Many people followed the system of chain migration, sending one family member ahead to become stable for the other family members to follow. [3], Showed the prevalence of the African originating HAP-L in major cities: Maywood, IL (n= 100, 16.61%), New York (n= 93, 18.23%), Pittsburgh (n= 84, 11.24%), Baltimore (n=96, 24.89), Charleston, S.C. (n=94, 12.92%), New Orleans (n=105, 10.75%). Of the major cities, Charleston S.C. has the lowest amount of European admixture followed by the northern city Philadelphia, Pennsylvania. The extent of heterogeneity, the limited weight of European admixture, and cultural dynamics of Legacy African Americans can be understood through the previously mentioned migration patterns, and by reconstructing reproductive events that altered gene flow. Not only was there a major flux of LAA’s who went north, once in urban cities the overall population grew rapidly. 

MtDNA 

Due to the frequent migrations of African North American descendants over the last 400 years, analyzing mitochondrial DNA (mtDNA) is one of the first steps to reconstructing their maternal ancestral story. The mtDNA haplotypes capture trends between ethnic groups and larger populations. As people and populations migrate and reproduce more frequently, more diversity is seen within ethnic groups while also allowing for haplotype sharing between ethnic groups. The location of mtDNA is within the mitochondria where it is present in hoop-like shape. A region of mtDNA known as the hypervariable segment I (HVS-I) is specifically used to determine haplogroups. The HVS-I region is preserved between generations, is usually non-recombinant, and contains polymorphic sites that are used to infer migration patterns and molecular evolution of populations (McClean, 2003). Mitochondrial DNA, however, is limited in that it does not characterize nuclear DNA and the admixture dynamics of the entire human genome.

Our theory is that Legacy African Americans genetically, and more so maternally descend from the Sea Islands and coastal Low country that insulated the Gullah Geechee. Gullah Geechee is an amalgamation of African ethnic groups brought to Georgia, North and South Carolina, and parts of the upper Florida coast. They were expert rice cultivators, managed waterways, and cultivated indigo, and Sea-Island cotton. They forced to the United States from the Gold Coast, Senegambia, Bight of Benin, Bight of Bonny, Upper Guinea, and West-Central Africa.

(see figure 1). [4], found that over 40% came from West-Central Africa including nations like Angolans and Congolese. Research suggests that 120,000 legally documented and up to 200,000 illegally documented enslaved Africans came through the Port of Charleston (Curtin, 1969) (James and Campbell, 1981). Of the estimated 300,000 who came to the United States, roughly 40% came through the Port of Charleston, South Carolina. Today we can visualize the preservation of African genetics and biocultural diversity in the Gullah Geechee. Due to the extreme heat and malaria-infested swamps in the Low country, slave owners visited plantations less frequently. The protective mechanism of the Duffy allele kept the African descendants better fit for the environment. The insulation allowed for admixture to occur more exclusively between the diverse African ethnic groups; and it allowed cultural practices, rituals, and beliefs to be shared and remembered intergenerationally while forming a new culture in the process. In Charleston (and surrounding Sea Islands) the African population ranged from 43-93% of the total population. Often in many colonial port cities such as New Orleans, Charleston, and Chesapeake Bay, a caste system develops with various levels of European admixture which became indirectly proportionate to the social station [2,15]. In South Carolina, Gullah Geechee communities showed less overall European admixture (<10%) than compared with the Lowcountry area which is less than 30 miles inland. However, there was more interbreeding with Europeans as people left the sea island coast headed inland [2].  

Method 1-2

Howard University approved this research as IRB-20-MED-78; however, the original review and approval were done by the University of South Carolina, as the African American Roots project. All participants were de-identified, and the dataset only included participant numbers and associated haplogroups. To complete an ancestral analysis of study populations, we will use secondary data from this dataset: Ely, B., Wilson, J. L., Jackson, F., & Jackson, B. A. (2006). African American mitochondrial DNAs often match mtDNAs found in multiple African ethnic groups. BMC biology, 4, 34. https://doi.org/10.1186/1741-7007-4-34. This data set comprises approximately n=79 African Americans who self-identified as Gullah-Geechee and a sample of African American DNAs (n=110) obtained from the Armed Forces DNA Identification Laboratory (AFDIL). A comparative analysis of mtDNA haplotypes was completed using R to complete Pearson’s Chi-Squared and frequency tables. All additional statistical analyses were performed using SAS 9.1. To analyze the potential impact of Gullah Geechee on the Legacy African American population, population growth rates for colonial and present time periods were conducted.

Results

A total of 189 mtDNA samples were analyzed to assess the distribution of haplogroups between Gullah Geechee African Americans and African American individuals.

Figure 1: Proportions of enslaved Africans brought to historic Carolina coastal ports from 17th to 19th centuries CE, [16].

Another rationale for analyzing mtDNA in Legacy African Americans is to find an association of evolutionary and genomic mechanisms that influence the prevalence of cardiovascular disease phenotypes in the broader African North American population. Cardiovascular Disease (CVD) is a major health disparity in ANA communities [17]. Years after the previously mentioned migrations, the Stroke Belt: [which is the southeast of the United States, consisting of the following states:] Georgia, North and South Carolina, Florida, Arkansas, Louisiana, Mississippi, and Alabama. This being still home to a disproportionate number of ANA’s [18]. These descendants of former enslaved Africans tend to have an incidence of hypertension, stroke, and other cardiovascular co-morbidities. The Center for Disease and Control (CDC) noted that there is 2 to 4 times more like to experience mortality by stroke in comparison to other regions of the United States. Understanding that one of the Stroke Belt unresearched contributors being genetic influence. Although this dataset did not include cardiovascular health-related data, our aim is to also provide a theory on how CVD phenotypes potentially and disproportionately occur in African North Americans. 

Ethics: This research was reviewed and approved by the Pennington Biomedical Research Center Institutional Review Board (Study #2023-051-PBRC). The study was determined to be Exempt under Category 4(ii), which permits secondary research using identifiable private information or biospecimens when data are recorded in a way that prevents direct or indirect identification of participants, and when no contact or re-identification occurs.

Acknowledgements

We gratefully acknowledge Dr. Bert Ely of the University of South Carolina for generously providing access to the mtDNA datasets foundational to this research and for establishing the comparative framework upon which this study builds. His earlier work on African and African American mitochondrial haplotypes made this analysis possible. We also thank the researchers and participants involved in the original African American Roots project, whose contributions continue to advance understanding of African-descended genetic diversity. Additional appreciation is extended to our colleagues and collaborators who offered guidance throughout this project.

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