יוג'ין קונין (מכון הבריאות הלאומי, ארה"ב)
יום חמישי, 2.4.2009, 13:30
Comparative genomics and systems biology reveal several surprising universals of genome evolution such as the distribution of evolution rates across genes, the distribution of paralogous gene family size, and connections between expression and evolution rate. The existence of these universals calls for simple, general models of evolutionary processes akin to those used in statistical physics (eg, birth and death processes), and at least in some cases, such models seem to explain the observed universal patterns. These general evolutionary models do not explicitly include selection suggesting that the basic processes underlying evolution are non-adaptive. Therefore, one of the basic “good practice” rules in evolutionary biology seems to be: Seek a non-adaptive null model of any process or phenomenon before invoking adaptations. Where evidence of selection is seen, the subject of selection is often not a specific function of gene/protein but rather robustness to malfunction or, more generally, maintenance of the basic organization of genome/cell. The quest for simple, even law-like regularities underlying evolution does not seem to be futile. The applicability of simple models to the basic processes of evolution does not contradict the “evolution as tinkering” metaphor of Francois Jacob: the specific outcomes of these regular processes involve a strong element of contingency, and are modulated by adaptive tinkering. In general terms, evolutionary biology is not dramatically different from physics/astrophysics/cosmology: the basic processes obey law-like patterns but the specific outcomes are determined by chance conditioned by adaptation, and are unpredictable – within the applicable constraints.
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