Cancer's Role in the Origin and Evolution of Complex Animals
Graham's radical proposal that lethal cancer in juveniles -- cancer selection -- played a significant role in the evolution of complex animals first appeared in 1983 when the Journal of Theoretical Biology published his LetterCancer and Evolution: Synthesis. A second LetterCancer and Evolution: Amplification was published in JTBin the following year.
He expanded the theory and presented arguments in favor of its adoption in his 1992 bookCancer Selection: the new theory ofevolution. In the book Graham identifies many fundamental animal characteristics which he claims are inadequately explained by conventional theory -- but which make sense with his proposed radical revision.
He argues that the emergence of complex animals from simpler multicellular ancestors must have involved a mechanism that was exclusive to complex animals, something that would account for the great precision required to construct the complex organ systems found in only in the Bilateria.
He postulates that cancer killed uncountable numbers of immature animals and concludes that the resulting accumulation of defenses against the disease enabled the emergence of complexity. In all evolving animal lineages selection favored utmost precision in the construction of all cells in order to avoid death of the organism resulting from imprecision in a single cell. This imperative of exactness at the level of individual somatic cells permitted the emergence of complex tissue, organs and organisms.
Without meticulous construction of individual cells complex organs could not exist. Without cancer selection multicellular life would not have evolved beyond the level of plants and jellyfish, organisms which, according to Graham's theory, never experienced lethal cancer.
Graham's idea thus synthesizes cancer and "evo-devo", the evolution of animal development.
For a fascinating account of Graham's decades-long ongoing struggle to get his idea accepted by the scientific community, as well as for links to his JTB Letters, a Nature review of his book, and recently-published papers that lend support to his radical ideas go toCancer Selection II.
Note:To read significant excerpts from Cancer Selection visitGoogle Books.