This study attributes the Y chromosome R1b to slave traders, but this is unlikely, as one inland African tribe the Ouldeme is almost totally R1b. You see this haplotype in Berbers, so it’s probably from them, before the Neolithic revolution swamped them with E3b1b. this would make it another marker of the Eurasian back migration into Africa. As this study says.
Some English family called Revis shows up positive for one of the world rarest Y chromosome clades from Guinea Bissau (A1). They are thought be be the descendants of an African slave, some time in the Georgian era. It’s amazing how DNA gets about.
The Guinea-Bissau Y chromosome pool is characterized by low haplogroup diversity (D = 0.470, sd 0.033), with the predominant haplogroup E3a*-M2 shared among the ethnic clusters and reaching a maximum of 82.2% in the Mandenka people. The Felupe-Djola and Papel groups exhibit the highest diversity of lineages and harbor the deep-rooting haplogroups A-M91, E2-M75 and E3*-PN2, typical of Sahel’s more central and eastern areas. Their genetic distinction from other groups is statistically significant (P = 0.01) though not attributable to linguistic, geographic or religious criteria. Non sub-Saharan influences were associated with the presence of haplogroup R1b-P25 and particular lineages of E3b1-M78.