They get that date by assuming humans didn't bring it to the island though, they don't do anything to rule that out: >"Barring the possibility that humans intr

They get that date by assuming humans didn't bring it to the island though, they don't do anything to rule that out: >"Barring the possibility that humans introduced multiple species-specific SIV lineages to the wild monkey populations of Bioko, the mainland and island SIVdrl variants must have been evolving independently since Bioko became isolated ~10,000 yr B.P., and perhaps longer given the high levels of genetic diversity seen within local SIV populations." http://www.sciencemag.org/cgi/content/abstract/329/5998/1487 http://www.sciencemag.org/cgi/content/abstract/329/5998/1487 Interesting stuff. I hadn't thought of this until now, but from these few papers I don't think anyone has tried very hard to rule out the human to simian transmission idea.