V. Life's Corporeal Evolution Develops, Encodes and Organizes Itself: An Earthtwinian Genesis Synthesis

4. Multicellular Fauna and Flora Organisms in Transition

Jung, Heekyung, et al. The Ancient Origins of Neural Substrates for Land Walking. Cell. 172/4, 2018. In a paper noted in the New York Science Times, an eleven member team from the USA, Australia, and Singapore, based at NYU School of Medicine, describe for the first time a rudimentary neural basis for the transition from an aquatic phase to mobile terrestrial creatures. As a surmise, it would appear that this fins to feet procession seems written into life’s oriented evolutionary advance.

Walking is the predominant locomotor behavior expressed by land-dwelling vertebrates, but it is unknown when the neural circuits that are essential for limb control first appeared. Certain fish species display walking-like behaviors, raising the possibility that the underlying circuitry originated in primitive marine vertebrates. We show that the neural substrates of bipedalism are present in the little skate Leucoraja erinacea, whose common ancestor with tetrapods existed ∼420 million years ago. Leucoraja exhibits core features of tetrapod locomotor gaits, including left-right alternation and reciprocal extension-flexion of the pelvic fins. This network encodes peripheral connectivity modules that are distinct from those used in axial muscle-based swimming and has apparently been diminished in most modern fish. These findings indicate that the circuits that are essential for walking evolved through adaptation of a genetic regulatory network shared by all vertebrates with paired appendages. (Abstract)

Kaiser, Dale. Building a Multicellular Organism. Annual Review of Genetics. 35/103, 2001. The same process of symbiosic association occurs in the formation of an organism as it did when diverse bacteria evolved and joined to form nucleated cells.

Multicellular organisms appear to have arisen from unicells numerous times. Multicellular cyanobacteria arose early in the history of life on Earth. Multicellular forms have since arisen independently in each of the kingdoms and several times in some phyla. If the step from unicellular to multicellular life was taken early and frequently, the selective advantage of multicellularity may be large….The capacity for signaling between cells accompanies the evolution of multicellularity with cell differentiation. (103)

Kapheim, Karen, et al. Genomic Signatures of Evolutionary Transitions from Solitary to Group Living. Science. 348/1139, 2015. At the frontier of joining this popular major transitions model with a consistent genetic-like basis, some 70 scientists with multiple postings in the USA, China, Denmark, Spain, Switzerland, Germany, Brazil, Canada, and Saudi Arabia, add further credibility of life’s apparent insistence to arise by iterating the same cycle and form from entity to community. This vectorial emergence proceeds in kind from biomolecular and bacterial stages onto groups within civilizations. See also Climbing the Social Ladder: The Molecular Evolution of Sociality by Sandra Rehan and Amy Toth in Trends in Ecology & Evolution (Online June 2015).

The evolution of eusociality is one of the major transitions in evolution, but the underlying genomic changes are unknown. We compared the genomes of 10 bee species that vary in social complexity, representing multiple independent transitions in social evolution, and report three major findings. First, many important genes show evidence of neutral evolution as a consequence of relaxed selection with increasing social complexity. Second, there is no single road map to eusociality; independent evolutionary transitions in sociality have independent genetic underpinnings. Third, though clearly independent in detail, these transitions do have similar general features, including an increase in constrained protein evolution accompanied by increases in the potential for gene regulation and decreases in diversity and abundance of transposable elements. Eusociality may arise through different mechanisms each time, but would likely always involve an increase in the complexity of gene networks. (Abstract)

Kaveh, Kamron, et al. Games of Multicellularity. Journal of Theoretical Biology. Online May, 2016. As the quotes advise, with Carl Veller and Martin Nowak, Harvard University, Program for Evolutionary Dynamics, researchers apply game theory models to life’s persistent transition from single cells to cellular organisms to propose a better explanation.

Evolutionary game dynamics are often studied in the context of different population structures. Here we propose a new population structure that is inspired by simple multicellular life forms. In our model, cells reproduce but can stay together after reproduction. They reach complexes of a certain size, n, before producing single cells again. The cells within a complex derive payoff from an evolutionary game by interacting with each other. The reproductive rate of cells is proportional to their payoff. We consider all two-strategy games. We study deterministic evolutionary dynamics with mutations, and derive exact conditions for selection to favor one strategy over another. Our main result has the same symmetry as the well-known sigma condition, which has been proven for stochastic game dynamics and weak selection. For a maximum complex size of n=2 our result holds for any intensity of selection. For n≥3n≥3 it holds for weak selection. As specific examples we study the prisoner's dilemma and hawk-dove games. Our model advances theoretical work on multicellularity by allowing for frequency-dependent interactions within groups.

To put it concisely, the evolution of multicellularity is often studied in a framework that does not adequately account for the interactions of cells within a group. In this paper, we place the evolution of multicellularity into an explicitly game-theoretic framework. Evolutionary game dynamics is the study of frequency dependent selection. The success of a genotype (or phenotype or strategy) depends on the frequency of different genotypes in the population. Evolutionary game dynamics was initially studied in well-mixed and infinitely large populations using deterministic differential equations. More recently it has moved to finite population sizes using stochastic dynamics. Evolutionary games are also studied in structured populations. A game-theoretic approach to the evolution of multicellularity allows us to generalize the traditional framework by accounting for frequency-dependent competition within multicellular units. The primary goal of our paper is to understand how the population structure of simple multicellularity affects the outcome of biological games. (3)

Kirk, David. A Twelve-Step Program for Evolving Multicellularity and a Division of Labor. BioEssays. 27/3, 2005. For the subject evolution of the algae genus Volvox cateri, the 12 stages run from “incomplete cytokinesis” to “bifurcated cell division program.” What is of note is that the constant process of nested differentiation and symbiotic emergence repeats once more.

The origin of multicellular organisms with a division of labor is also one of the most interesting and complex problems in the field of evolution of development, because it presumably involved – at a minimum – a transition from cellular autonomy to cellular cooperation, the invention of novel morphogenetic mechanisms, and the elaboration of novel spatial patterns of differential gene expression. (299)

Klein, Jan and Naoyuki Takahata. Where Do We Come From? Berlin: Springer, 2002. An extensive essay on the evolutionary reconstruction of molecular and phylogenetic pathways which lead to homo sapiens.

Knoll, Andrew. Life on a Young Planet. Princeton: Princeton University Press, 2003. The story of the early diversification of multicellular organisms in the Cambrian seas. Three tasks are cited: a narrative history, how this came to be known, and a look for general principles at work. These result in a view of evolution as an accumulative process which involves the coevolution of Earth and its biospheric life. Altogether this creates a special bioplanet which life proceeds to take over and molds for its own advantage.

Knoll, Andrew. The Multiple Origins of Complex Multicellularity. Annual Review of Earth and Planetary Sciences. 39/217, 2011. The Harvard paleobotanist surveys from the second decade of the 21st century how intricate organisms came into somatic form from simpler eukarotes. This advance is said to have occurred in six clades: animals, embryophytic land plants, florideophyte red algae, laminarial brown algae, and two groups of fungi. Key facilitation was provided by intercellular adhesion, communication, and a developmental program.

Koseska, Aneta, et al. Cooperative Differentiation through Clustering in Multicellular Populations. Journal of Theoretical Biology. 263/2, 2010. A European team quantifies the importance of intercellular communication and functional variability to the formation of globally collective, viable cellular societies.

Larson, Ben, et al. Biophysical Principles of Choanoflagellate Self-Organization. Proceedings of the National Academy of Sciences. 117/1303, 2020. UC Berkeley and Harvard biologists including Nicole King describe how these cellular cousins are likewise moved by and exemplify these common formative agencies, as they proceed toward multicellular developments. Once again a natural genesis uses the same independent source system at each instance.

Comparisons among animals and their closest living relatives, the choanoflagellates, have begun to shed light on the origin of animal multicellularity and development. Here, we complement previous genetic perspectives on this process by focusing on the biophysical principles underlying choanoflagellate colony morphology and morphogenesis. Our study reveals the crucial role of the extracellular matrix in shaping the colonies and leads to a phase diagram that delineates the range of morphologies as a function of the biophysical mechanisms at play. (Significance)

The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates having a funnel shaped collar of interconnected microvilli at the base of a flagellum.

Li, Xuhung, et al. Compartmentalization of Metabolism between Cell Types in Multicellular Organisms. Current Opinion in Systems Biology. 29/100407, 2022. By way of the latest computational methods, UM Medical School, Worcester researchers find that life’s vivifying anatomy and physiology is arrayed from genomes and cells all the way to animals and ourselves. A philoSophia view then wonders where such actual features as nested modular units, wholes within emergent wholes, symbiotic unions came from in the first place. However might we peoples be able to realize that all this phenomena reveals a greater genesis with its own animate existence.

In multicellular organisms, metabolism is compartmentalized at many levels, including tissues and organs, different cell types, and subcellular phases. In this way, a coordinated homeostatic system is created where each unit contributes to the production of energy and biomolecules to carry out specific metabolic tasks. Here we show that computational methods with integrative metabolic network modeling and omics data offers an opportunity to reveal metabolic states at the level of organs, tissues and individual cells. (Abstract excerpt)

Libby, Eric and Paul Rainey. A Conceptual Framework for the Evolutionary Origins of Multicellularity. Physical Biology. 10/3, 2013. Massey University, New Zealand, and Max Planck Institute for Evolutionary Biology, Germany, researchers help explain life’s inherent persistence to form nested wholes of corporeal and societal entities, which appear as a “manifest emergence of individuality.” But it continues to be curious that as such a scalar reiteration becomes validated, as it takes this common form of a self-organizing, complex adaptive system, as stuck in the old selection school, no thought of or search for a formative cause has yet occurred. See also Fisher, Roberta, et al, herein.

The evolution of multicellular organisms from unicellular counterparts involved a transition in Darwinian individuality from single cells to groups. A particular challenge is to understand the nature of the earliest groups, the causes of their evolution, and the opportunities for emergence of Darwinian properties. Here we outline a conceptual framework based on a logical set of possible pathways for evolution of the simplest self-replicating groups. Central to these pathways is the recognition of a finite number of routes by which genetic information can be transmitted between individual cells and groups. We describe the form and organization of each primordial group state and consider factors affecting persistence and evolution of the nascent multicellular forms. Implications arising from our conceptual framework become apparent when attempting to partition fitness effects at individual and group levels. These are discussed with reference to the evolutionary emergence of individuality and its manifestation in extant multicellular life—including those of marginal Darwinian status. (Abstract)

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