To understand why there are multiple blood types in the Human Race we need to understand where both RH-Positive and RH-Negative blood types part-originated from. Zechariah Sitchen talks about this in his book, "The Lost Books of Enki", of the Annunaki being the creator gods of the Human Race. Now these Annunaki supposedly created a race of beings, but not necessarily us Humans. We as Humans were derived from the first race of creation, created by the Annunaki. The first Race of creation on Earth was, "The Nephilem". These Nephilem were created by the Annunaki using Homo Erectus DNA and Annunaki DNA. Homo Erectus DNA was RH-Positive. The Annunaki DNA was RH-Negative. Now, we know the part-origins of the RH-Positive and RH-Negative Blood type. Going further into the "Multiple" blood types, I will say this: "One of the Nephilem women and one of the Annunaki male procreated and gave birth to a child." (Zechariah Sitchin - The Lost Books of Enki). The Race of this child is Unknown but could be the first Human. The blood type of this child is Unknown, but it could have either been RH-Negative or RH-Positve. This story end here due to lack of knowledge.