Sudden origins: A general mechanism of evolution based on stress protein concentration and rapid environmental change

Abstract

A major theme in Darwinian evolutionary theory is that novelty arises through a process in which organisms and their features are gradually transformed. Morgan provided Darwinism and the evolutionary synthesis with the idea that minor mutations produce the minuscule morphological variations on which natural selection then acts, and that, although mutation is random, once a process of gradual genetic modification begins, it becomes directional and leads to morphological, and consequently organismal, transformation. In contrast, studies on the role of cell membrane physical states in regulating the expression of stress proteins in response to environmental shifts indicate the existence of a downstream mechanism that prevents or corrects genetic change (i.e., maintains "DNA homeostasis"). However, episodic spikes in various kinds of environmental stress that exceed an organism's cells' thresholds for expression of proper amounts of stress proteins responsible for protein folding (including stochastically occurring DNA repair) may increase mutation rate and genetic change, which in turn will alter the pattern of gene expression during development. If severe stress disrupts DNA homeostasis during meiosis (gametogenesis), this could allow for the appearance of significant mutational events that would otherwise be corrected or suppressed. In evolutionary terms, extreme spikes in environmental stress make possible the emergence of new genetic and consequent developmental and epigenetic networks, and thus also the emergence of potentially new morphological traits, without invoking geographic or other isolating mechanisms.

Do Molecular Clocks Run at All? A Critique of Molecular Systematics

“…For, aside from UVinduced point mutation, there is no other constant source of mutation in the physical world, and spontaneous mutation rates are low (approximately 10 −8 to 10 −9 ) (Maresca and Schwartz 2006). Indeed, cells contain myriad stress and other proteins that eliminate potential change from becoming established in the genome and maintain DNA homeostasis, which can be derailed only by the most extreme environmental stresses (ibid.).…”

“…In short, the notion that molecules of germ cells-DNA, RNA, and proteins and transcription factors necessary, e.g., for DNA repair, protein folding, chaperone functions, and control of signal transduction pathways, which are necessary for the survival of cells and their bearers-are in states of perpetual change is not, in our present understanding of cell biology, tenable. This does mean that "molecular change" does not occur; only that mechanisms provoking such change in germ cells are likely instantaneous and stochastic and probably often lethal (Maresca and Schwartz 2006)-which will preclude their persistence into future generations.…”

Changes in Membrane Fluid State and Heat Shock Response Cause Attenuation of Virulence

“…The regularity with which these defects emerge under stressful conditions during embryogenesis of Metazoa and plants across different taxa suggests that HSPs may play a rather general role in the proper expression of developmentally regulated genes (21). These findings suggest that, since these genes and the transcription factors involved are different and evolutionarily distant, the effect of HSPs (which are highly conserved in sequence and functions) is stochastic and not protein specific.…”

Reflections on Systematics and Phylogenetic Reconstruction

“…To revive discussion of the relevance of a hypothetico-deductive-essentially Hennigian or cladistic-approach to phylogenetic reconstruction is at least informative in recognizing that any phylogenetic statement is only a hypothesis or theory of relatedness. Here the contrast between Popper's argument against evolutionary proof (Popper 1968) and Kuhn's argument to the contrary (Kuhn 1996) is relevant. For while there is only one ''true'' way in which physical (including chemical) properties and attributes must interact, and there is also only one, true evolutionary history of life, the nature of inquiry each science dictates are not equivalent.…”