Animal emergence during Snowball Earths by thermosynthesis in submarine hydrothermal vents

Darwin already commented on the lateness in the fossil record of the emergence of the animals, calling it a valid argument against his theory of evolution^1^. This emergence of the animals (metazoans: multicellular animals) has therefore attracted much attention^2-5^. Two decades ago it was reported that extensive global glaciations (Snowball Earths) preceded the emergence^6-7^. Here we causally relate the emergence and the glaciations by invoking benthic sessile^8-11^ thermosynthesizing^12-13^ protists that gained free energy as ATP while oscillating in the thermal gradient between a submarine hydrothermal vent^14^ and the ice-covered ocean. During a global glaciation their size increased from microscopic to macroscopic due to the selective advantage of a larger span of the thermal gradient. At the glaciation's end the ATP-generating mechanisms reversed and used ATP to sustain movement. Lastly, by functioning as animal organs, these protists then through symbiogenesis^15-17^ brought forth the first animals. This simple and straightforward scenario for the emergence of animals accounts for their large organ and organism size and their use of ATP, embryo and epigenetic control of development. The scenario is extended to a general model for the emergence of biological movement^18^. The presented hypothesis is testable by collecting organisms near today's submarine hydrothermal vents and studying their behaviour in the laboratory in easily constructed thermal gradients

Evolution of self-maintaining cellular information processing networks

We examine the role of self-maintenance (collective autocatalysis) in the evolution of computational biochemical networks. In primitive proto-cells (lacking separate genetic machinery) self-maintenance is a necessary condition for the direct reproduction and inheritance of what we here term Cellular Information Processing Networks (CIPNs). Indeed, partially reproduced or defective CIPNs may generally lead to malfunctioning or premature death of affected cells. We explore the interaction of this self-maintenance property with the evolution and adaptation of CIPNs capable of distinct information processing abilities. We present an evolutionary simulation platform capable of evolving artificial CIPNs from a bottom-up perspective. This system is an agent-based multi-level selectional Artificial Chemistry (AC) which employs a term rewriting system called the Molecular Classifier System (MCS). The latter is derived from the Holland broadcast language formalism. Using this system, we successfully evolve an artificial CIPN to improve performance on a simple pre-specified information processing task whilst subject to the constraint of continuous self-maintenance. We also describe the evolution of self-maintaining, crosstalking and multitasking, CIPNs exhibiting a higher level of topological and functional complexity. This proof of concept aims at contributing to the understanding of the open-ended evolutionary growth of complexity in artificial systems

Integrating Horizontal Gene Transfer and Common Descent to Depict Evolution and Contrast It with ‘‘Common Design

Horizontal gene transfer (HGT) and common descent interact in space and time. Because events of HGT co-occur with phylogenetic evolution, it is difficult to depict evolutionary patterns graphically. Tree-like representations of life’s diversification are useful, but they ignore the significance of HGT in evolutionary history, particularly of unicellular organisms, ancestors of multicellular life. Here we integrate the reticulated-tree model, ring of life, symbiogenesis whole-organism model, and eliminative pattern pluralism to represent evolution. Using Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2), a bifunctional enzyme in the glycolytic pathway of amoeba, we illustrate how EhADH2 could be the product of both horizontally acquired features from ancestral prokaryotes (i.e. aldehyde dehydrogenase [ALDH] and alcohol dehydrogenase [ADH]), and subsequent functional integration of these enzymes into EhADH2, which is now inherited by amoeba via common descent. Natural selection has driven the evolution of EhADH2 active sites, which require specific amino acids (cysteine 252 in the ALDH domain; histidine 754 in the ADH domain), iron- and NAD1 as cofactors, and the substrates acetyl-CoA for ALDH and acetaldehyde for ADH. Alternative views invoking ‘‘common design’’ (i.e. the non-naturalistic emergence of major taxa independent from ancestry) to explain the interaction between horizontal and vertical evolution are unfounded

The Evolution of Diversity

Since the beginning of time, the pre-biological and the biological world have seen a steady increase in complexity of form and function based on a process of combination and re-combination. The current modern synthesis of evolution known as the neo-Darwinian theory emphasises population genetics and does not explain satisfactorily all other occurrences of evolutionary novelty. The authors suggest that symbiosis and hybridisation and the more obscure processes such as polyploidy, chimerism and lateral transfer are mostly overlooked and not featured sufficiently within evolutionary theory. They suggest, therefore, a revision of the existing theory including its language, to accommodate the scientific findings of recent decades

What Is It Like To Become a Bat? Heterogeneities in an Age of Extinction

In his celebrated 1974 essay “What Is It Like to Be a Bat?,” Thomas Nagel stages a human-bat encounter to illustrate and support his claim that “subjective experience” is irreducible to “objective fact”: because Nagel cannot experience the world as a bat does, he will never know what it is like to be one. In Nagel’s account, heterogeneity is figured negatively—as a failure or lack of resemblance—and functions to constrain his knowledge of bats. Today, as white-nose syndrome threatens bat populations across North America, might figuring heterogeneity positively, as a condition of creativity, open up new modes of receptivity and responsiveness to species extinctions? This essay turns to philosophies of becoming and to recent research in the biological sciences to explore this possibility. I suggest that attending to the heterogeneity of experience alerts us to more public dimensions of our being and may thereby work against the tendency to understand and experience ourselves as self-contained and closed off from one another and the world we share in common. This may in turn enhance our sense of entanglement with the events, bodies, and forces on the “outside” of experience, including bats and the white-nose syndrome with which they are afflicted today. Such an affirmation of heterogeneity as a condition of creativity holds the greatest promise for multispecies ethics today, I propose, when it is joined to an affirmation of incompatibilities within and between things as a real force of suffering and destruction in a heterogeneous world

Morphogenesis by symbiogenesis

Here we review cases where initiation of morphogenesis, including the differentiation of specialized cells and tissues, has clearly evolved due to cyclical symbiont integration. For reasons of space, our examples are drawn chiefly from the plant, fungal and bacterial kingdoms. Partners live in symbioses and show unique morphological specializations that result when they directly and cyclically interact. We include here brief citations to relevant literature where plant, bacterial or fungal partners alternate independent with entirely integrated living. The independent, or at least physically unassociated stages, are correlated with the appearance of distinctive morphologies that can be traced to the simultaneous presence and strong interaction of the plant with individuals that represent different taxa

Life Sustains Life 2. The ways of re-engagement with the living earth

This article argues that we need to learn from the living earth how living systems sustain themselves and use this knowledge to transform our unsustainable and destructive social systems into sustainable and symbiotic systems within systems. I first set out what I take to be four central features of sustainable living systems according to the life and earth sciences. Secondly, I set out what I take to be the main features of our unsustainable social system that cause damage to the ecosphere on the one hand and give rise to the illusion of independence from it on the other hand. I then turn to several ways of responding to the sustainability crisis that are informed by this way of thinking about our interdependent relationship in and with ecosocial systems. These are ways of dis-engaging from our unsustainable practices, beginning to engage in practices of re-engaging and reconnecting socially and ecologically, and thus beginning to bring into being unalienated and sustainable ways of life on earth. If the symbiotic interdependency thesis of the first section is true, then participants in these connecting practices should be empowered in reciprocity by the interdependent relationships they connect with, and thus initiate expanding virtuous cycles. This reciprocal empowerment is discussed in the final section

Arts of Living on a Damaged Planet: Ghosts and Monsters of the Anthropocene by Anna Lowenhaupt Tsing, Heather Anne Swanson, Elaine Gan, and Nils Bubandt

Review of Anna Lowenhaupt Tsing, Heather Anne Swanson, Elaine Gan, and Nils Bubandt\u27s Arts of Living on a Damaged Planet: Ghosts and Monsters of the Anthropocene