Every drop of blood in your body is doing something ancient. It is carrying oxygen, fighting infections, clotting wounds, and patrolling for threats, a set of tasks so fundamental to animal life that nearly every creature with a backbone does some version of the same thing.

You probably don't think much about the blood running through your veins on a daily basis.

Every drop of blood in your body is doing something ancient. It is carrying oxygen, fighting infections, clotting wounds, and patrolling for threats, a set of tasks so fundamental…