My Story of the Chuck...

Rh Negative Recessive Blood Types!

If a chicken (Rh++) and a duck (Rh- -) try to mate, they do NOT create a CHUCK (Rh+/-) naturally....BUT if there was already an animal that was a CHUCK (Rh+/-) it would have an easier time mating with both the chick (Rh++) and the duck (Rh- -), because it is 1/2 of what it is trying to mate with... I think the confusion in the body of the "CHUCK" (Rh+/-) creates a "dis-eased" condition in the body via the immune system.
I also think the Rh- vs Rh+ stats have to be more like 15-20% Rh-, 25-30% RH+ and the rest 50-60% Rh+/- in the United States, thus recognizing the recessive carriers are their own sub category; as they are neither Rh+ or Rh- but BOTH...they are Chucks!
Hope this helps you understand how I began down this road of research.  My parents, siblings and children are all CHUCKS (Rh+/-) .... I am the only rare DUCK! (Rh-/-)