ISIS Report 11/03/09
ISIS Scientific Preprint
Development and Evolution Revisited
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
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To appear in Handbook of Developmental Science, Behavior and Genetics
(K. Hood, C. Halpern, G. Greenberg, & R. Lerner, eds.), Blackwell
Publishing, New York, 2009
Abstract
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.
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