VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies
5. Multicellular Fauna and Flora Organisms
Butterfield, Nicholas. Animals and the Invention of the Phanerozoic Earth System. Trends in Ecology and Evolution. 26/2, 2011. A Cambridge University scientist offers a novel insight as to how this era which covers the whole time since the Cambrian period some 540 mya to date has been largely affected by the presence of creaturely species. As multicellular organisms dubbed “pelagic eumetazoa” rose to upper seas levels and land living they became “ecosystems engineers” for all manner of niches, along with a major effects on the biosphere.
Animals do not just occupy the modern biosphere, they permeate its structure and define how it works. Their unique combination of organ-grade multicellularity, motility and heterotrophic habit makes them powerful geobiological agents, imposing myriad feedbacks on nutrient cycling, productivity and environment. Most significantly, animals have ‘engineered’ the biosphere over evolutionary time, forcing the diversification of, for example, phytoplankton, land plants, trophic structure, large body size, bioturbation, biomineralization and indeed the evolutionary process itself. This review surveys how animals contribute to the modern world and provides a basis for reconstructing ancient ecosystems. Earlier, less animal-influenced biospheres worked quite differently from the one currently occupied, with the Ediacaran–Cambrian radiation of organ-grade animals marking a fundamental shift in macroecological and macroevolutionary expression. (Abstract)
Celiker, Hasan and Jeff Gore. Cellular Cooperation: Insights from Microbes. Trends in Cell Biology. 23/1, 2012. MIT biophysicists Celiker, a Turkish-American graduate student, and Gore, an assistant professor and director of the MIT Evolutionary Systems Biology Laboratory offer a sophisticated quantification from a bacterial basis of how life consistently evolves and forms by a balance of diversity and unity toward more complex organisms. And so many of these reports beg an independent genetic-like source that so informs and is manifest in these nested iterations. See also by the authors “Competition between Species can Stabilize Public-Goods Cooperation within a Species” in Molecular Systems Biology (8/621, 2012).
Cooperation between cells is a widespread phenomenon in nature, found across diverse systems ranging from microbial populations to multicellular organisms. For cooperation to evolve and be maintained within a population of cells, costs due to competition have to be outweighed by the benefits gained through cooperative actions. Because cooperation generally confers a cost to the cooperating cells, defector cells that do not cooperate but reap the benefits of cooperation can thrive and eventually drive the cooperating phenotypes to extinction. Here we summarize recent advances made in understanding how cooperation and multicellularity can evolve in microbial populations in the face of such conflicts and discuss parallels with cell populations within multicellular organisms. (Abstract)
Chen, Zhanqi, et al. Prolonged Milk Provisioning in a Jumping Spider. Science. 362/1052, 2018. In a paper which received popular notice, ten zoologists and botanists in China report for the first time that even insect species possess and this prime maternal attribute of vertebrate mammals. In regard, evolutionary life seems to hold to a common physiology, anatomy and behavioral repertoire which is then availed and repeated in creaturely kind.
Lactation is a mammalian attribute, and the few known nonmammal examples have distinctly different modalities. We document here milk provisioning in a jumping spider, which compares functionally and behaviorally to lactation in mammals. The spiderlings ingest nutritious milk droplets secreted from the mother’s epigastric furrow until the subadult stage. Maternal care, as for some long-lived vertebrates, continues after the offspring reach maturity. These findings demonstrate that mammal-like milk provisioning and parental care for sexually mature offspring have also evolved in invertebrates, encouraging a reevaluation of their occurrence across the animal kingdom, especially in invertebrates. (Abstract)
Conway Morris, Simon. Evolution: Bringing Molecules into the Fold. Cell. 100/1, 2000. The Cambridge paleontologist on convergent pathways in genetic networks, neural mechanisms and fish echolocation.
Cooper, Rory, et al. An Ancient Turing-like Patterning Mechanism Regulates Skin Denticle Development in Sharks. Science Advances. 4/11, 2018. We cite this paper by University of Sheffield, Oxford and Florida biologists as another current finding that natural evolution seems to avail an independent mathematical source code which then appears in exemplary, recurrent effect across the anatomy and physiology of Metazoan creaturely kingdoms.
Vertebrates have a vast array of epithelial appendages, including scales, feathers, and hair. The developmental patterning of these diverse structures can be theoretically explained by Alan Turing’s reaction-diffusion system. However, the role of this system in epithelial appendage patterning of early diverging lineages such as the cartilaginous fishes is poorly understood.. We demonstrate through simulation models that a Turing-like mechanism can explain shark denticle patterning. This mechanism bears remarkable similarity to avian feather patterning, suggesting deep homology of the system. We propose that a diverse range of vertebrate appendages, from shark denticles to avian feathers and mammalian hair, use this ancient and conserved system. (Abstract)
Dewel, Ruth Ann. Colonial Origin for Eumetazoa: Major Morphological Transitions and the Origin of Bilaterian Complexity. Journal of Morphology. 243/1, 2000. A contribution to the 21st century project to reread and reconstitute evolution as informed by comparative, integrative and complexity concepts. A persistent process is described whereby entities such as microbes, cells or organisms evolve into integral assemblies or colonies. An increased complexity emerges as these stages form a nested hierarchy. Salient trends include a specialization or division of labor, the formation of modular components and the subsequent coalescence of further levels of organic organization. And at each transition, the rudimentary colony is said to be engaged in a task of individuation.
Duclos, Kevin, et al. Investigating the Evolution and Development of Biological Complexity under the Framework of Epigenetics. Evolution & Development. Online July, 2019. University of Calgary cell biologists contribute to this nonlinear revolution, while it goes on largely unawares, to reinterpret life’s gestation by way of innate, iterative, scalar topologies and source forces. Here the recent expansion of genomic activity to include influences beyond nucleotides, aka epigenetics broadly conceived, is applied as one more generative factor at work in evolutionary developments.
Biological complexity is a key component of evolvability, yet its study has been hampered by a focus on evolutionary trends of complexification and inconsistent definitions. Here, we demonstrate the utility of bringing complexity into the framework of epigenetics to better investigate its utility as a concept in evolutionary biology. We first analyze the existing metrics of complexity and explore its link with adaptation and developmental mechanisms. We then consider how epigenetics shapes developmental and evolutionary trajectories. We argue that epigenetics itself could have emerged from complexity because of a need to self‐regulate. Our goal is not to explain trends in biological complexity but to help develop and elucidate novel questions in the investigation of biological complexity and its evolution. (Abstract excerpt)
Eldredge, Niles. The Pattern of Evolution. New York: Freeman, 1998. The American Museum of Natural History curator argues for a broader theory that goes beyond “internalized competition between genes” to recognize hierarchical scales with a law-like continuity with the physical environment.
Fenchel, Tom. The Origin and Early Evolution of Life. Oxford: Oxford University Press, 2002. A basic text which relates the updated version of a sequential repetition of the occurrence and assembly of modular components into higher level entities.
Our ideas about evolution of life imply the integration of self-replicating molecules into a genome, horizontal transfer of genes form one individual to another, that the origin of eukaryotic cells implied the integration of endosymbiotic bacteria, and that multicellular organisms arose from cell colonies. (2)
Fernandez-Valverde, Selene, et al. Inference of Developmental Gene Regulatory Networks Beyond Classical Systems: New Approaches in the Post-genomic Era. Integrative and Comparative Biology. 58/4, 2018. The entry by research biologists from Mexico and Chile within a Genomic, Ecological and Paleontological Insights into the Early Evolution of Animals section is a good example, after decades of isolate gene studies, of realizations that equally active interlinkages are a major complementary factor. (Once again the particulate elements need be found first before connected altogether.) For concurrent views see The Vertebrate Limb: An Evolving Complex of Self-Organizing Systems by Stuart Newman, et al below and Monostability, Bistability, Periodicity and Chaos in Gene Regulatory Networks (search Qiang Lai in GCS). We also note The Molecular Quest for the Origin of the Animal Kingdom by Jordi Paps and Oxygen and the Energetic Requirements of the First Multicellular Animals by Sally Leys and Amanda Kahn.
The advent of high-throughput sequencing technologies has revolutionized the way we understand the transformation of genetic information into morphological traits. Elucidating the network of interactions between genes that govern cell differentiation through development is one of the core challenges in genome research. These networks are known as developmental gene regulatory networks (dGRNs) and consist largely of the functional linkage between developmental control genes, cis-regulatory modules, and differentiation genes. Much progress has been made in determining these gene interactions mainly in classical model systems, including human, mouse, sea urchin, fruit fly, and worm. Here, we give a historical overview on the architecture and elucidation of the dGRNs and summarize approaches to unravel them, highlighting the range of possibilities of integrating multiple technical advances. Such new knowledge will not only lead to greater insights into the evolution of molecular mechanisms underlying cell identity and animal body plans, but also into the evolution of morphological key innovations in animals. (Abstract excerpts)
Fisher, R. M., et al. The Evolution of Multicellular Complexity: The Role of Relatedness and Environmental Constraints. Proceedings of the Royal Society B. July, 2020. University of Copenhagen bioecologists including J. J. Boomsma provide further natural properties that impelled unicell organisms to join into beneficial groupings. Their prevalence then seen to imply how often this imperative (obligate) major transition has occurred.
A major challenge in evolutionary biology has been to explain variations in multicellularity across independently evolved lineages from slime moulds to vertebrates. Social evolution theory highlights relatedness in vitally complex forms. However, there is a need to extend this perspective to relative environments. In this paper, we test (John) Bonner's 1998 hypothesis that such settings are crucial to its course, with aggregative multicellularity evolving more frequently on land and clonal multicellularity more often in water. Using a combination of scaling theory and phylogenetic comparations, we describe complex organizations across 139 species spanning 14 independent transitions to multicellularity. Our results show that physical environments impact how multicellular groups form, and thus affect the major evolutionary transition to obligate multicellularity. (Abstract)
Fisher, Roberta, et al. Group Formation, Relatedness, and the Evolution of Multicellularity. Current Biology. Online June, 2013. As the Abstract details, Roberta Fisher and Stuart West, Oxford University zoologists, and biologist Charlie Cornwallis, Lund University, Sweden, propose that if life’s propensity to form into more complex entities via wholes within wholes is set within the major transitions scale an even better understanding of how and why this happens can be gained. It is worth noticing that while this ascension is good for individuality, a sense of and referral to a causal, formative source remains elusive. So this scenario is still seen as confirmation of how natural selection acts alone.
The evolution of multicellular organisms represents one of approximately eight major evolutionary transitions that have occurred on earth. The major challenge raised by this transition is to explain why single cells should join together and become mutually dependent, in a way that leads to a more complex multicellular life form that can only replicate as a whole. It has been argued that a high genetic relatedness (r) between cells played a pivotal role in the evolutionary transition from single-celled to multicellular organisms, because it leads to reduced conflict and an alignment of interests between cells. We tested this hypothesis with a comparative study, comparing the form of multicellularity in species where groups are clonal (r = 1) to species where groups are potentially nonclonal (r ≤ 1). We found that species with clonal group formation were more likely to have undergone the major evolutionary transition to obligate multicellularity and had more cell types, a higher likelihood of sterile cells, and a trend toward higher numbers of cells in a group. More generally, our results unify the role of group formation and genetic relatedness across multiple evolutionary transitions and provide an unmistakable footprint of how natural selection has shaped the evolution of life. (Abstract)