Almost on the heels of the 1900 ABO blood group discovery, some scientists began plotting out various associations of the blood types with certain human traits, ranging from personality to appropriate diets, the so-called blood group diet being merely one of the latest such fads.

In Singapore, most people are Rhesus positive (A+, B+, O+, AB+), and only less than 1% of the population are Rhesus negative (A-, B-, O- and AB-). This Rhesus-negative blood type is found most commonly in Singaporean Indians (6%), compared to other racial groups (less than 1%).