Morphogenetic evolution with physical influences

Morphogenesis is the process in which cells, tissues, organs and embryos acquire orderedness, patterns, shapes and higher order organizations. Most morphogenetic processes are known to be controlled by genetic programs, and experimental and theoretical studies have indeed provided strong support that evolutionary changes of morphogenetic mechanisms can largely be attributed to genetic modifications. Studies in the last decades had begun to reveal the contribution of physical mechanisms in a growing number of morphogenetic contexts, wherein they act in parallel with, and at times independent of, genes, leading to stochastic and self-organized behaviors. The involvement of physical mechanisms raises intriguing questions as to how they might influence the evolutionary dynamics of morphogenesis, and whether there might be themes and patterns that have not been previously conceptualized. In this review, we examine an ensemble of physical factors and mechanical processes shown recently in empirical and theoretical studies to be critical contributors of morphogenetic mechanisms. We ask whether some of these might have arisen prior to, and possibly shaped, the emergence of genetic programs. We consider conceptual frameworks that could support these hypothetical scenarios, and further propose a 'leap-and-patch' model, whereby morphogenetic systems exhibit a phase transition-like shift to a distinct phenotypic regime in response to changes in physical parameters ('leaps'), thereby facilitating genetic accommodation or evolutionary innovation of novel morphogenetic mechanisms ('patches'). Our discussion suggests the possibility that physical factors might be more than a contributor of morphogenesis, but a facilitator of evolutionary transition or innovation.