Good point. Combined with the botanical and other evidence though, which is from before the period of South American contact I think you’re referring to (post-Columbus?), this can’t be discarded.
From the article at the link: “Because most of Thorsby’s volunteers came from one extended family, he was able to work out when the HLA genes entered their lineage. The most probable first known carrier was a woman named Maria Aquala, born in 1846. Crucially, that was before the slave traders arrived in the 1860s and began interbreeding with the islanders.”
As an aside, I think ‘intermarrying’ would have been a better choice of word in the article.
Given that slavers aren’t known for marrying their prey, I suggest interbreeding is exactly the right term.
Vulgar, but then the practice of slavery is extremely vulgar in reality.