Mosaic evolution
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This type of evolution is seen when functional systems evolve at different rates in the same life form.
In neodarwinist Theory of Evolution, as postulated by Stephen Jay Gould, there is room for differing development, when a life form matures earlier or later, in shape and size.
This is due to allomorphism.
Organs develop at differing rhythms, as a creature grows and matures. Thus a 'heterochronic clock', as Jay Gould (1977) postulates, has three variants: 1) time, as a straight line; 2) general size, as a curved line; 3) shape, as another curved line.
When a creature is advanced in size, it may develop at a smaller size; alternatively, it may maintain his original size or, if delayed, it may result in a larger sized creature. That is insufficient to understand heterochronic mechanism.
Size must be combined with shape, so a creature may retain paedomorphic features if advanced in shape or present recapitulatory appearance when retarded in shape. This names are not very indicatives, as theories of development were very confusing in past (see: Jay Gould - 1977).
So a creature in his ontogeny may combine heterochronic features in six vectors, although Jay Gould considers that there exist some binding with growth and sexual maturation.
A creature may, for example, present some neotenic features and retarded development, resulting in new features derived from an original creature only by regulatory genes. Jay Gould defends that almost of human features, when compared with proximal apes were from this nature, not implying a lot of change in structural genes, as classically was considered.
[edit] References
- Jay Gould, S. (1977); "Ontogeny and Phylogeny", Belknap Press of Harvard University Press, seventeenth printing, 2003, 501p.
