"Another fact that seems overlooked is the most important reason the parasite attaches itself to the host; Sustenance. What made the human blood, once again, attractive to the Gorilla parasite?"

According to a phylogenic tree produced by P.A. Apoil & A. Blancher (1999), the RHD gene which codes for the Rh D antigen on the Red Blood Cells of humans is a much more recent adaptation than its ancestral room-mate the RHCE gene. They've produced a scientific paper showing the evolution of the RH gene in mammals; from mouse to man. This maybe reason for the recent neanderthal revelation, but I've found nothing so far on the RH gene morphology of the neanderthal. What Apoil and Blancher do show however is that the RHCE is older (i.e. the ancestral gene) and closer to the Gorilla's RH genes; the RHD gene is a recent duplication which occured closer to the separation of Homo and our 98% cousin, the Chimps. Only those who have been paying attention will recognize the significance of these facts.