TP53 and cancer: For example, while the ancestral gene in the p53 family of tumor suppressors arose in sea anemones to protect the germline from DNA damage, p53 itself and its explicit somatic tumor-suppressor function arose in early vertebrates like cartilaginous fish that first developed regenerative populations of somatic stem and progenitor cells that made vertebrates more susceptible to cancers (Belyi et al. 2010).