It’s important to keep in mind that the slaves/captives reexported via Cape Verde mostly in the 1500’s/1600’s were almost always enslaved Africans born on the mainland and not born on the islands themselves. Cape Verde being known for turning African born slaves into “seasoned” Ladino slaves (baptism + basic Portuguese/Creole language skills). Besides the Ladino’s and the socalled Bozales (“fresh of the boat” slaves) a third distinction was made (according to Sandoval 1624) of socalled Naturales, that is Cape Verde born slaves. They were the most expensive slaves but judging from slave trade registers only rarely to be seen in Latin America and usually kept on Cape Verde itself. See for example the chart for Maranhão I posted earlier where 8 Cape Verdean born slaves are mentioned among a sample of 7573 slaves, representing a mere 0,1%, while there’s 2359 Upper Guinean born slaves in total, representing over 30%.
So while we can assume that Cape Verdeans and a selected subgroup of Afrodescendants in the Hispanic Americas and Northern Brazil might share similar ethnic/regional African roots, this doesn’t mean that these ancestral connections were brought about by Cape Verdean persons, it’s rather two Afro-diasporean branches from the same tree rooted in Upper Guinea than Cape Verde being the tree itself! It’s very illuminating in this regard to review the recent results obtained by personal DNA testing which seem to confirm a socalled Upper Guinean founding effect for many Hispanics:
It’s interesting to contrast this Afro-diasporic connection with the genuinely Cape Verdean Diaspora which is well known in migration studies because it provides such a stark example of how a population can be forced to migrate in great numbers. According to most estimates nowadays more Cape Verdean descendants are living abroad than on the islands themselves! And the USA is sometimes said to host almost as many Cape Verdean descendants as Cape Verde itself. Using a very liberal definition though as it is known that many multigenerational Cape Verdean descendants have intermarried with Americans of all backgrounds: African Americans, Whites, Latino’s and even Native Americans!
“The United States and Cabo Verde have strong historical roots. As early as the 1740s, U.S. whaling ships began recruiting crews from the islands of Brava and Fogo, and other ships from the American colonies routinely anchored in Cabo Verdean ports to trade. The tradition of emigration to the United States began at that time and continues today. Some 4,000 American citizens now reside in the country, while Cabo Verde’s Diaspora in the United States (primarily Massachusetts and Rhode Island) almost rivals the islands’ current population of over 500,000. The first U.S. consulate in sub-Saharan Africa was established in Cabo Verde in 1818.” (source: http://www.state.gov/r/pa/ei/bgn/2835.htm)
Strictly speaking a Cape Verdean Diaspora already existed in the 1500’s when Cape Verdean born traders started to settle on the mainland of Africa because of better trading opportunities (the socalled “Lançados”). However mass migration from the islands is generally thought to have started in the 1800’s when visiting whaling ships from the USA picked up Cape Verdean seamen. These crew members started settling in New England and eventually brought over family, friends and relatives. The history of Cape Verdean migration to the US is very fascinating because it’s actually the first time Africans migrated to the USA out of their free will and even in some instances on sailing ships, operated and owned by themselves! This article has some more detailed info.
Also Wikipedia has a good article on Cape Verdean Americans
The USA wasn’t the only destination though for Cape Verdean migrants, as can be clearly seen from the map above. The migration of Cape Verdean seamen to Argentina is another fascinating saga that also started already in the late 1800’s/early 1900’s. I have distant family there myself. There have even been Cape Verdean whalers who ended up all the way in the Pacific/Hawaii! I was astonished to find several Cape Verdean descended DNA cousins/matches on 23andme from not only Hawai but even Tonga!!!