The Origin, Evolution and Development of Bilateral Symmetry in Multicellular Organisms (1207.3289v1)

Abstract: A computational theory and model of the ontogeny and development of bilateral symmetry in multicellular organisms is presented. Understanding the origin and evolution of bilateral organisms requires an understanding of how bilateral symmetry develops, starting from a single cell. Bilateral symmetric growth of a multicellular organism from a single starter cell is explained as resulting from the opposite handedness and orientation along one axis in two daughter founder cells that are in equivalent developmental control network states. Several methods of establishing the initial orientation of the daughter cells (including oriented cell division and cell signaling) are discussed. The orientation states of the daughter cells are epigenetically inherited by their progeny. This results in mirror development with the two founding daughter cells generating complementary mirror image multicellular morphologies. The end product is a bilateral symmetric organism. The theory gives a unified explanation of diverse phenomena including symmetry breaking, situs inversus, gynandromorphs, inside-out growth, bilaterally symmetric cancers, and the rapid, punctuated evolution of bilaterally symmetric organisms in the Cambrian Explosion. The theory is supported by experimental results on early embryonic development. The theory makes precise testable predications.

• The paper demonstrates that bilateral symmetry originates from two founder daughter cells with mirrored orientations and identical control networks.
• It employs computational modeling to integrate genetic instructions with epigenetic orientation dynamics during embryogenesis.
• Simulation results link symmetry mechanisms to evolutionary events, offering fresh insights into rapid morphological diversification.

An Analytical Overview of Bilateral Symmetry in Multicellular Organisms

The paper by Eric Werner offers a comprehensive computational theory elucidating the origin and development of bilateral symmetry in multicellular organisms. This paper introduces a sophisticated model that systematically addresses the ontogenetic roots and evolutionary implications of bilateral symmetry, showcasing the role of developmental control networks (DCNs) and epigenetic factors in shaping symmetrical morphologies from a unicellular origin.

Key Contributions and Claims

1. Theory of Bilateral Symmetry Development: Werner posits that bilateral symmetry develops via two founder daughter cells which exhibit opposite orientations yet share identical developmental control network states. These cells mirror each other along an axis perpendicular to the future plane of division, a mechanism attributed to epigenetically inherited orientation states. The intrinsic focus on the opposite handedness and spatial orientation sets the foundation for symmetrical organisms.
2. Multilayer Genetic and Epigenetic Interactions: The paper emphasizes that the orientations and the developmental states of cells are jointly dictated by the intrinsic interpretive-executive systems (IES) of the cells. Such systems decode developmental networks, reflecting that symmetry development is not only guided by genetic instructions but also influenced significantly by cell orientation dynamics.
3. Broad Phenomenological Explanations: Werner's model unifies a variety of phenomena within its explanatory framework, including symmetry breaking, situs inversus, and gynandromorphic development. The theory also offers insights into less traditional concepts such as inside-out growth and bilaterally symmetric cancers, underscoring the theoretical robustness across diverse developmental anomalies.
4. Evolutionary Implications and the Cambrian Puzzle: A salient aspect of the paper is the exploration of the Cambrian Explosion, an era marked by rapid morphological diversification. Werner postulates that symmetry transformations, governed primarily by epigenetic orientations coupled with network mutations, underlie rapid evolutions, suggesting an untapped evolutionary landscape facilitated by symmetry inversion and sub-symmetry configurations.
5. Computational Model and Predictions: The document delineates computational simulation outcomes that corroborate its hypotheses. Simulations of multicellular development in a virtually conceived 4D space-time provide concrete models predicting cellular orientations and developmental outcomes. It bolds predictive insights such as epigenetically driven bilateral symmetry in early embryogenesis and potentially symmetrical cancers.

Potential Impact and Future Directions

Werner's paper reinvigorates discussions on the integration of computational modeling with traditional biological inquiry, advocating for a nuanced exploration of DCNs. The implications for fields such as developmental biology and evolutionary computation are substantial, providing novel angles to investigate organismal evolution and morphogenetic controls.

Moving forward, the paper invites experimental investigations into the molecular underpinnings that align with its computational predictions. An exploration into developmental control networks, particularly their interpretive-executive capacities, could substantiate the computational model. Moreover, it opens debates about the evolutionary pressures favoring bilateral symmetry and how transformative shifts in genetic and epigenetic interactions could have propelled early multicellular evolution.

In essence, the paper offers a potent synthesis of theory and computational forecasting, paving the way for deeper interdisciplinary research into bilateral symmetry's developmental and evolutionary dimensions. This represents a significant stride in understanding the complex architectures governing organismal development from a single cell to intricate, bilaterally symmetrical multicellular systems.