Genetic mutations slowly accumulated over a lifetime change blood production after 70 years of age

Driver mutations lead to a decrease in the diversity of stem cells that produce blood cells.

Scanning electron micrograph (SEM) of human white and red blood cells. The red cells are responsible for the transport of oxygen from the lungs to the rest of the body. The white cells have varied functions but are all involved in the immune response. Magnification x 12,000. Credit: David Spears FRPS FRMS/Getty Images