Neoplastic progression is an evolutionary process in which somatic cells mutate and compete for resources. Those mutants that tend to proliferate and survive more than others will tend to spread. In some cases, this process ends with the evolution ofa malignant neoplasm that kills its host.In the 1970's Sir Richard Peto pointed out that, at a first approximation, every cell in a body has a chance of becoming cancerous, and so, all things being equal, an organism with more cells should have a higher cancer incidence than an animal with fewer cells. The same argument can be made for lifespan: longer-lived organisms should be more vulnerable to cancer than organisms with a shorter lifespan. However, they are not. Cancer mortality rates are roughly constant across mammals, at about 5%, despite 6 orders of magnitude differences in size and 2 orders of magnitude differences in lifespan. This mismatch between theory and observation is called P'eto's Paradox.
展开▼
