The African diaspora: mitochondrial DNA and the Atlantic slave trade

Abstract

Between the 15th and 19th centuries ad, the Atlantic slave trade resulted in the forced movement of approximately 13 million people from Africa, mainly to the Americas. Only approximately 11 million survived the passage, and many more died in the early years of captivity. We have studied 481 mitochondrial DNAs (mtDNAs) of recent African ancestry in the Americas and in Eurasia, in an attempt to trace them back to particular regions of Africa. Our results show that mtDNAs in America and Eurasia can, in many cases, be traced to broad geographical regions within Africa, largely in accordance with historical evidence, and raise the possibility that a greater resolution may be possible in the future. However, they also indicate that, at least for the moment, considerable caution is warranted when assessing claims to be able to trace the ancestry of particular lineages to a particular locality within modern-day Africa.

Figure 1

Frequency profiles of the major haplogroups in Africa and haplogroups of recent African ancestry in the Americas and Eurasia

Figure 2

Scatterplot of the first two principal components based on haplogroup frequencies. For practical reasons, the “Other-L3” and “Other non Afr” haplogroup categories, with coordinates (0.0171, 0.4210) and (0.6680, 0.0768), respectively, are not displayed in the PC plot. Codes and references for populations are as follows: America: Af = African American (Vigilant et al. ; Handt et al. 1998); B1 = white Brazilian (Alves-Silva et al. 2000); B2 = African Brazilian (Bortolini et al. 1997), B3 = Bahía-Brazil (Santos et al. 2002); Co = Chocó, Ga = Garífuna (A. Salas, M. Richards, M.-V. Lareu, S. Silva, M. Matamoros, V. Macaulay, and A. Carracedo, unpublished data); Mx = Mexican (Green et al. 2000); Cr = Caribbean (Monsalve and Hagelberg 1997); St = Dominican Republic (Torroni et al. ; A.T., unpublished data). Northern Africa: Sh = West Saharan, Ma = Mauritanian, Mo = Berber, Mr = Moroccan non-Berber (Rando et al. 1998); Mc = Moroccan (Brakez et al. 2001); Eg = Egyptian (Krings et al. 1999); Mb = Mozabite (Côrte-Real et al. 1996); Ca = Canarian (Pinto et al. ; Rando et al. 1998). Western Africa: Ha = Hausa, Ka = Kanuri, Fu = Fulbe, So = Songhai, Tu = Tuareg (Watson et al. 1997); Yo = Yoruba (Vigilant et al. ; Watson et al. 1997); Sn = Senegalese, Sr = Serer, Wo = Wolof (Rando et al. 1998); Mn = Mandenka (Graven et al. 1995); Cv = Cabo Verde (Brehm et al. 2002). West-central Africa: Bo = Bubi, Sa = São Tomé (Mateu et al. 1997); Fg = Fang (Pinto et al. 1996); Bi = Biaka, Mt = Mbuti (Vigilant et al. 1991); An = Angola (Santos et al. 2002). Eastern Africa: Tk = Turkana, Sm = Somalian, Ki = Kikuyu (Watson et al. 1997); Nu = Nubian, Su = Nuba, Shilio, Duba, Nuer (Krings et al. 1999); Et = Ethiopian (Thomas et al. 2002). Southeastern Africa: M1 = Mozambique (Pereira et al. 2001); M2 = Mozambique (Salas et al. 2002). South Africa: K2 =!Kung, Kw = Khwe (Chen et al. 2000).

Figure 3

Phylogenetic network of shared mtDNA HVS-I sequence types of recent African ancestry in America, Eurasia, and Africa. The charts show: (a) the proportion in each main region of those specific haplotypes shared by >15 individuals (yellow frame), (b) the frequency distribution when the whole haplotypes are considered in each haplogroup with <16 individuals per haplotype (black frame), and (c) the frequency distribution of all shared haplotypes for each of the main lineages (L1, L2, and L3) (blue frame). In the bottom left corner, the chart shows the frequency distribution of the whole set of shared haplotypes (gray frame). Population codes correspond to those listed in the legend of figure 2.