The Black Story: Genetic history of Afro-Americans
When I am starting to write this article, according to John Hopkins University Covid-19 tracker there are already around confirmed 2.57 million cases of the novel corona virus pandemic all across the world taking over 176,000 lives since its first outbreak in Wuhan Province of China. It is well observed by now in different parts of the world that the vulnerability in terms of deaths and confirmed cases has shown some significant disparities with respect to sex, races and populations. Some weeks ago, when the disease started to take its rare form in the US, important observation of cases started to highlight high rate of vulnerability among black people in several news and research articles. It is very surprising to notice here that most of these articles all over the internet and print media do not explain what is the meaning of a black American, and who are the people typed under this category. It is both interesting and important to know about the ancestry of these people to understand the vulnerability of communities elsewhere in the world.
African continent has been a cradle for the birth of human (Tattersall I. Out of Africa: modern human origins special feature: human origins: out of Africa. Proc Natl Acad Sci U S A. 2009), the unique structure of human skull and post-cranial skeleton has been a distinguishing feature to identify the members of our genus. It is interesting to note that this is a well proven truth that the genus Homo originated in Africa in the form of hominids some 7 Ma, but also, this continent has continued to give birth to many new kinds of hominids since 2 Ma. The multi-regional or candelabra model of the origin of modern human suggests that after leaving the African continent, our ancestors gave rise to modern humans in multiple regions around the globe. In contrary to the candelabra theory, out-of-Africa theory is commended by larger group of researchers which suggests that there was a single migration out of the continent to replace the hominins in other parts of the world (López S, van Dorp L, Hellenthal G. Human Dispersal Out of Africa: A Lasting Debate. Evol Bioinform Online. 2016;11(Suppl 2):57–68. Published 2016 Apr 21. doi:10.4137/EBO.S33489).
The detailed genetic study of the modern day vast African population is distinct because of the variation of temperature and climate, diet and exposure to infectious agents all across the continent (Campbell MC, Tishkoff SA. African genetic diversity: implications for human demographic history, modern human origins, and complex disease mapping. Annu Rev Genomics Hum Genet. 2008;9:403–433.). The modern day migrations started in 17th-18th century in the form of slave trade, the Africans were transported knowingly or unknowingly from their homelands to the European and American (North and South) nations. The early slavery trade has been an important and inseparable part of the North American history which has helped in establishing by large, the wealth of economy in the west. The Africans transported to the American nations mainly the United States, were the inhabitants of the regions which is modern-day Gambia, Senegal, Guinea-Bissau and Mali; and west-central Africa, including what is now Angola, Congo, the Democratic Republic of Congo and Gabon, Ghana and Ivory Coast. The western coast of the African continent was the hub of the trade and this is the region where most of the modern-day Afro-american ancestry belongs to.
Reliable mt-DNA analyses, Y-chromosome haplotyping, presence of ancestry-informative markers, SNP studies have collectively resulted into well characterization of the Afro-american ancestry in the North American continent specifically in the United States. The present day population of the US is a result of population admixture taking place since the mid of 17th century. It is rather interesting to note that there are many articles and books written mostly by Afro-americans that how they differ between native-born and foreign-born among themselves. In short ‘Black’ could be a rather lose term to elaborate a large percentage of population of African-american people in the United States.
The genetic make-up and composition of any human being in any part of the world is the mirror image of the historical connection between DNA and his history combined. It would not be therefore incorrect to say that the DNA of the Blacks in America has undergone significant changes from their original ancestors back there in African homelands. These differences and the arisen distinctions in the Afro-american genome is however are largely hidden from the world because of the focus of the genetic studies considering this population as a population of totally different geographic origin ignoring the similarities or novelties. It remains true that most of the Black DNA comes from Africa but it is also an established fact that there is a proven admixture of European ancestry, whose descendants are in better economic conditions than there African brothers and sisters in the United States. According to studies, the proportions of European ancestry in African-american genome is 25%, which is obviously a significant amount.
The studies related to the genetics of the populations all across the world is a need of time. This would help in exploring the positive and negative aspects of populations at genetics level, which in turn would help in understanding their vulnerabilities towards biologic and non-biologic agents. We cannot ignore the fact today that the disparities among the populations all around the globe are our only hope to guard us from unknown and incurable diseases.
