These tidewater and deep southern GAYs (also "Guy"s) are not within my area of expertise, but I believe that most of the GAYs whose roots trace back to Georgia and Alabama will eventually be found to have descended also from certain GAY families who settled early in the Virginia tidewater region. Some material on these GAYs will be found on
my GAY Surname page, but I particularly refer people interested in these lines to
the GAY DNA Project where a number of pedigrees back to these areas have been posted.
Most of the GAYs with this background sort into Lineage Group 1 (the test results for which are accessible from this "Patriarchs" page by clicking the "y-Results" link in the top menu bar). What this means is that every male GAY whose DNA test comes out Lineage 1 is related to all the others through a common ancestor, although that ancestor my go back as many as 700 years. However, in the case of this GAY Lineage 1, the test results show that the common ancestor for most dates back only to the 1600s (or perhaps a few generations before) when the earliest GAYs, including the man I call "Henry of Nansemond" first appeared in that county, and in its child county, Isle of Wight.
Most of the people who have tested at FTDNA are pretty serious researchers of their lines, and the deep lineage connections encourage one to think more broadly and creatively about one's ancestral possibilities, and so can be helpful in suggesting ways around road blocks.
To test, one needs to find a male relative surnamed GAY who would be willing to swab his cheek and mail in the test kit, plus $149 for the preferred FTDNA 37-marker test (on sale for $119 just through tomorrow, July 31st - I'm hoping that the price for this test will come down permanenty before very long). Lesser tests from FTDNA or from competitors like Ancestry.com, even though cheaper, are not worth the money IMO. Incidentally, I am myself an administrator of one of the FTDNA surname projects, though not the GAY project, so I know whereof I speak.
DNA testing is no substitute for research but it can help point the serious researcher in the right direction, and hook him/her up with others who are exploring the same byways.