Time reversal in biological systems.

Fundamental physical laws provide us appropriate descriptions of the basic behavior of nature. Science possesses a hierarchical structure with various levels of complexity and organization. This extends from the physics of elementary particles and atomic constituents, to the chemistry of molecules, to the biology of the cell and multicellular levels, up to an individual and beyond. Molecular biology thus has its roots based upon fundamental physical descriptors of macromolecules and chemical reactions. The purpose of this paper is to relate an operation in physics, time reversal symmetry, to the realm of biology. This is done with regard to the process of carcinogenesis. Tumor development and progression can be considered a microcosm of evolution, on the level of an individual organism, as well as from the aspect of evolutionary lineage. The driving forces of selection inherent in malignancy can be considered to result in the emergence of a new biological species, which is characterized by reproductive immortality and a remarkable equivalence with our unicellular ancestors. Thus, by its very nature, carcinogenesis as a closed system conceptually represents a reversal of motion with respect to order, stability and evolutionary standards of time.