However, from what I've learned about chickens over the years (breeding them in fact) there's really only one species ~ but the wild progenitor lives in South America. The "wild chickens" in Africa are simply domesticated chickens that have "reverted to the wild", kind of like Arkansas razorbacks.
I think the reason "they" decided there were two species of chickens is that otherwise, if there were only one, and it originated in the Americas, that would mean there had to have been pre-Columbian contact, but with the Indians discovering Africa.
I suspect in the long run this question will be resolved to the satisfaction of everybody, as well as the chickens.
Seriously (well, maybe not so seriously), if somebody told me when I was 12 years old that I could have all the food I wanted, a dozen women a day, different women each day, rotating at a rate that there is no way that I would ever recognize them, and the only bad thing was that I would be shot in the head at the age of 25 and served up in a stew... I'd have signed that paper in a heartbeat. As long as there was beer. A man has to have his priorities, after all. ;-)
Or, horror of horrors, that Africans discovered the Americas.
(I am not for one second suggesting that you - or I - think like that, just that sometimes people tend to blind themselves to things that they don't like, and that this tends to result in BS research)