"JENA, GERMANY—A recent study suggests that three men buried some 500 years ago in a cemetery at a colonial hospital in Mexico City belonged to the first generation of Africans to arrive in the New World, according to a report in Science Magazine. The skeletal remains of the three men were unearthed in the 1980s during the construction of a subway line. At the time, researchers suspected the remains might have belonged to people born and raised in cultural traditions based in West Africa based on the modifications made to their teeth. Genetic analysis of the remains by Rodrigo Barquera and Johannes Krause of the Max Planck Institute for the Science of Human History revealed that all three men had ancestors from West Africa, while the analysis of the chemical composition of their teeth showed that they all grew up in West African ecosystems. Barquera and Krause added that the men’s skeletons show signs of trauma, including gunshot wounds, heavy physical labor, broken bones, malnutrition, and anemia, which suggests they had been enslaved, and were perhaps among the first victims of the transatlantic slave trade."

I'm sure their treatment was abysmal, although it's hard to know if some of the malnutrition at least was from their time in Africa, although perhaps they go into that in the paper.

They did bring diseases with them from Africa.

The mass grave in which the men were buried was attached to a hospital established around 1530 to treat the region’s indigenous population, which endured brutal treatment at the hands of Spanish colonizers and was decimated by European diseases such as smallpox. Workers happened upon the grave while constructing a new subway line in downtown Mexico City between 1988 and 1994.The skulls—unearthed in 1992—stood out among hundreds due to their owners’ decoratively filed front teeth, reports the Times. This pointed style was previously observed among enslaved Africans in Portugal."

"Remnants of disease found on the skeletons allowed the scientists to sequence the pathogens’ genomes and gain a clearer understanding of how the transatlantic slave trade spread various ailments. One of the men had a strain of the virus that causes hepatitis B; another suffered from yaws, a syphilis-like bacterial infection of the skin, bones and cartilage.

The diseases’ viral and bacterial genomes were genetically similar to strains most often seen in Africa, leading the researchers to suggest that enslaved Africans may have been responsible for inadvertently introducing these diseases to the Americas.
“We are always so focused on the introduction of diseases from the Europeans and the Spaniards,” Johannes Krause, an ancient DNA expert at Max-Planck and co-author of the new paper, tells the Times, “that I think we underestimated also how much the slave trade and the forceful migration from Africa to the Americas contributed also to the spread of infectious diseases to the New World.”
Radiocarbon dating suggests the men lived between 1436 and 1626. Given the hospital’s age and the fact that the remains were found in the deepest, oldest strata of the burial site, the three were likely laid to rest in the middle of the 16th century."

See the paper:

People forget about the approximately 5% SSA in Mexicans.