Only 15% Of People Have Rh-Negative Blood -- A Biologist Explains Why

A biologist’s explanation focuses on why Rh-negative blood persists in human populations despite reproductive risks tied to it. The plus or minus in blood type refers to the presence of the RhD protein on red blood cells: Rh-positive people have it, while Rh-negative people do not. The article describes how an Rh-negative woman carrying an Rh-positive baby can develop antibodies after exposure, and those antibodies can attack red blood cells in a later Rh-positive pregnancy—creating a reproductive cost natural selection would be expected to remove. Instead, roughly one in seven people with European ancestry are Rh-negative, and the piece cites gene-deletion and broken-gene mechanisms from studies published in Blood.