[3] P53, p63, and p73 have similar features in their gene structures and functions but have also diverged evolutionarily.
The p53 family evolved from an ancestor gene in unicellular life.
[4] The ancestor gene functioned in germ line DNA protection early invertebrates.
[5] In invertebrates, the ancestor gene resembled p63/p73 as it contained the sterile alpha motif (SAM) domain.
[7] In vertebrates, p53 began the role of protecting the somatic cells and acting as a tumor suppressor.