Directionality In Evolution

With the cybernetic narrative of ecosystem development (the New Ecology) now before us, it is perhaps useful to revisit the question of whether the process of biotic evolution might exhibit any form of directionality? Perhaps an unequivocal response is premature, suffice it here to compare the differences in the dynamics of ontogeny, ecosystem development, and evolution. With ontogenetic development, there is no denying the directionality evident in the developing organism. Convention holds that such direction is "programmed" in the genomic material, and no one is going to deny the degree of correspondence between genome and phenome. The question remains, however, as to where does the agency behind such direction reside? It is awkward, to say the least, to treat the genome as some sort of homunculus that directs the development process. Genomic material such as DNA is unlikely to have evolved by random assembly, and outside its network of enzymatic and proteomic reactions it can do nothing of interest (Kauffman, 1993). Its role in ontogeny is probably best described as that of material cause, sensu Aristotle—it is materially necessary, but passive with respect to more efficient (again, sensu Aristotle) agencies that actively read and carry out the anabolic processes. As regards those processes, they form a network that indubitably contains autocatalytic pathways, each with its accompanying directions.

The entire scenario of ontogeny is rather constrained, and noise plays a distinct secondary role. In contrast, the role of genomes is not as prominent in the development of ecosystems (Stent, 1981). While some hysterisis is required of the participating species, the central agencies that provide directions (as argued above) are the autocatalytic loops among the species. The constraints among the species are nowhere near as tight as at the ontogenetic level, and noise plays a much larger role in the direction that a system takes over time.

Evolutionary patterns are not as stereotypical as those in ecological succession. What happens before some cataclysm can be very different from what transpires after the disaster. So evolutionary theorists are probably correct in pointing to random events as playing the larger role over the long run. It appears premature, however, to rule out directional processes altogether. Many species and their genomes survive catastrophes, as do entire autocatalytic ensembles of species at the level of the ecosystem. They provide a degree of history that helps to direct the course of evolution until the next upheaval.

This dynamic is already familiar to us from the workings of Polya's Urn, which we considered earlier. In fact, a reasonable simile would be to consider what might happen if Polya's Urn were upset after some 1000 draws and only a random subset of say 15 balls could be recovered and put back into the Urn to continue the process. Although the subsequent evolution of the ratio of red to blue balls might not converge very closely to what it was before the spill, some remnants of the history would likely keep the ratio from making an extreme jump. Suppose before the spill the ratio had converged rather tightly to 0.739852, and that after the accident ten red balls and five blue balls were recovered. It is exceedingly unlikely that the continuing process would converge to, say 0.25835.

And so it may be on the evolutionary theatre. Not all directions established by ecosystems during one era are necessarily destroyed by a catastrophe that initiates the next. Surviving directions are key to the evolutionary play during the next interval. Thermodynamic and other physical directions notwithstanding, anyone who argues that evolution involves only chance and no directionality is making an ideological statement and not a reasoned "conjecture" because ecosystem have directionality.

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