The first one was the human trade that led thousands of African slaves to the southern United States, and the second was the Great Migration period, which started around 1910, when millions of African-Americans entered New York, Chicago, and various other parts of America.
Among these African-Americans, 82.1 percent have African ancestors, 16.7 percent have European genes, and 1.2 percent show traces of American DNA.
The greatest challenges that the geneticists faced in finding the medical relevance of these diseases were that most of the African slaves in those times were captured from different genetic backgrounds, some of whom already had European or American ancestors.
This DNA research was mainly based on the study of X chromosome (women), as African slave women produced children with their white owners.
Along with Dr. Gravel, many other geneticists such as Dr. Burchard of U.C.-San Francisco; Alondra Nelson, the dean of social science at Columbia University; and Eimear E. Kenny, a geneticist at the Icahn School of Medicine at Mount Sinai in New York, have researched the reasons behind these African American genetic mixtures, their effects on Black Americans of today, and the diseases that may have occurred due to these genes.
