The Evolution of Vertebrate Blood Clotting by

Hemostasis is an essential physiological response to acute injury in organisms with a circulatory system. In the Darwinian struggle that drove early natural selection, only creatures that were capable of limiting blood loss could survive wounds or injuries that breeched a vessel. Vertebrates, from hagfish to primates, suffer acute injuries that would lead to exsanguination were adequate hemostasis not in place. The clotting of blood in response to injury is a primordial\ but highly efficient and complex affair, the analysis of which remains a challenge.