Rh-negative blood

Rh-negative blood refers to the blood group that lacks the protein Rh (Rhesus), and is typically linked to the ABO blood type (i.e. types A, B, O, AB are coupled with the Rh positive or negative, hence blood types like O Positive, A Positive, O Negative, &c.). This trait has been of certain interest among believers in ancient alien interactions with humanity, who have asserted it is evidence that humans have been modified by extraterrestrials.

As evidence of alien ancestry

 * Venus Venous Research Corporation, a California group founded by Bonnie and Mabel Royce in the 1970s;
 * Karen Hudes, who claimed that the world is clandestinely governed by homo capensis, a hominid-like species with enlarged craniums and copper-based, Rh-negative blood.