Who discovered human blood groups around 1900?

The discovery of human blood groups in 1900 is attributed to Karl Landsteiner, a pivotal moment in the field of transfusion medicine. He identified the existence of different blood types (A, B, AB, and O) based on the presence or absence of specific antigens on the surface of red blood cells. This discovery not only advanced our understanding of blood compatibility and transfusions but also paved the way for improvements in safe blood transfusion practices, reducing the risk of hemolytic reactions during transfusions.

Landsteiner's work provided the scientific foundation for blood typing, significantly impacting the clinical practice of blood transfusion and organ transplantation. His contributions were so important that he was awarded the Nobel Prize in Physiology or Medicine in 1930.

The other individuals mentioned, while significant in their own fields, did not contribute to the identification of blood groups. Jules Bordet was known for his work in immunology, Louis Pasteur was a pioneer in microbiology and immunization, and P. L. Mollison was influential in blood transfusion medicine, but they were not the first to discover blood groups.