From the article linked ... "Hauswirth said it contains genetic markers, or specific segments of DNA that are affiliated with one small subset of modern American Indians. This suggests that the Windover people did not reproduce with people from other groups,"
So I guess he means that the modern tribe are the only direct descendent's of this group. Also, interesting is that Windover is the site of the oldest known bottle gourd,
"At Windover, a bottle gourd, Lagenaria siceraria, was found carefully placed in one burial. The plant, a type of squash, is believed to have originated in Africa."
http://www.rps.psu.edu/0305/planted.html
Perhaps the people also have African origins.