More than 100 years after they were discovered, we’re still looking for an answer as to why blood types exist.

“Jeannie Peeper’s diagnosis meant that, over her lifetime, she would essentially develop a second skeleton. Within a few years, she would begin to grow new bones that would stretch across her body, some fusing to her original skeleton. Bone by bone, the disease would lock her into stillness. The Mayo doctors didn’t tell Peeper’s parents that. All they did say was that Peeper would not live long.”

A profile of celebrity astrophysicist Neil Tyson.