Mae-Wan Ho reviews recent evidence in support of the idea that evolutionary novelties arise from non-random developmental changes defined by the dynamics of the epigenetic system; and shows how the organism participates in shaping its own development and future evolution
Institute of Science in Society, Omnibus Business Centre, 39-41 North Road, London N7 9DP, UK, www.i-sis.org.uk
To appear in Handbook of Developmental Science, Behavior and Genetics (K. Hood, C. Halpern, G. Greenberg, & R. Lerner, eds.), Blackwell Publishing, New York, 2009
Recent advances in elucidating the molecular mechanisms of epigenetics – hereditary influences due to the environment - and the revival of interest in evolution and development (‘evo-devo’) have prompted me to revisit these related themes.
In a paper, “Beyond neo-Darwinism, an epigenetic approach to evolution“, published in 1979, we proposed that the intrinsic dynamics of developmental processes is the source of non-random variations that direct evolutionary change in the face of new environmental challenges. These evolutionary novelties are reinforced (canalized) in successive generations through cytoplasmic/ epigenetic mechanisms, independently of natural selection.
Subsequently, we demonstrated that canalisation can indeed occur without positive selection, in what appears to be a case of epigenetic inheritance. We also showed how the dynamics of the patterning process during development serves as the basis for a rational taxonomy of segmentation defects in Drosophila and phyllotaxis in plants that can offer strong predictions of phylogenetic transformations.
Recent findings from phylogenetic studies lend further support to our predictions that molecular evolution (microevolution) is decoupled from the evolution or organisms (macroevolution), and that the latter involves epigenetic reorganisation.
Unfortunately, current studies on evolution and development are still obsessed with the idea that genes control development and that new body patterns involve changes in gene regulation through natural selection. They have not taken on board new findings that increasingly blur the distinction between genetic and epigenetic, or the physicochemical dynamics of patterning processes that generate forms, where the real connections between evolution and development are to be found.
In the new holistic perspective, epigenetics mediates between the psychosocial and biological realms, and holds the key to how we can shape our own development and future evolution.