Can We Understand Evolution Without Symbiogenesis?

Situating physiology within evolutionary theory

Traditionally defined as the science of the living, or as the field that beyond anatomical structure and bodily form studies functional organization and behaviour, physiology has long been excluded from evolutionary research. The main reason for this exclusion is that physiology has a presential and futuristic outlook on life, while evolutionary theory is traditionally defined as the study of natural history. In this paper, I re-evaluate these classic science divisions and situate physiology within the history of the evolutionary sciences, as well as within debates on the Extended Evolutionary Synthesis and the need for a Third Way of Evolution. I then briefly point out how evolutionary physiology in particular contributes to research on function, causation, teleonomy, agency and cognition.

Reticulate evolution underlies synergistic trait formation in human communities

This paper investigates how reticulate evolution contributes to a better understanding of human sociocultural evolution in general, and community formation in particular. Reticulate evolution is evolution as it occurs by means of symbiosis, symbiogenesis, lateral gene transfer, infective heredity, and hybridization. From these mechanisms and processes, we mainly zoom in on symbiosis and we investigate how it underlies the rise of (1) human, plant, animal, and machine interactions typical of agriculture, animal husbandry, farming, and industrialization; (2) diet-microbiome relationships; and (3) host-virome and other pathogen interactions that underlie human health and disease. We demonstrate that reticulate evolution necessitates an understanding of behavioral and cultural evolution at a community level, where reticulate causal processes underlie the rise of synergistic organizational traits.

Teleonomy as a problem of self-causation

A theoretical framework is provided to explore teleonomy as a problem of self-causation, distinct from upward, downward and reticulate causation. Causality theories in biology are often formulated within hierarchy theories, where causation is conceptualized as running up or down the rungs of a ladder-like hierarchy or, more recently, as moving between multiple hierarchies. Research on the genealogy of cosmologies demonstrates that in addition to hierarchy theories, causality theories also depend upon ideas of time. This paper explores the roots and impact of both time and hierarchy thinking on causal reasoning in the evolutionary sciences. Within evolutionary biology, the Neodarwinian synthesis adheres to a linear notion of time associated with linear hierarchies that portray upward causation. Eco-evo-devo schools recognize the importance of downward causation and consequently receive resistance from the standard view because downward causation is sometimes understood as backward causation, considered impossible by adherents of a linear time model. In contrast, downward causation works with a spatial or presential time notion. Hybridization, lateral gene transfer, infective heredity, symbiosis and symbiogenesis require recognition of reticulate causation occurring in both space and time, or spacetime, between distinct and interacting ontological hierarchies. Teleonomy is distinct from these types of causation because it invokes the problem of self-causation. By asking how the focal level in a hierarchy can persist through time, self-causation raises philosophical concerns on the nature of duration, identity and individuality.

Testing the “(Neo-)Darwinian” Principles against Reticulate Evolution: How Variation, Adaptation, Heredity and Fitness, Constraints and Affordances, Speciation, and Extinction Surpass Organisms and Species

Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction form the building blocks of the (Neo-)Darwinian research program, and several of these have been called “Darwinian principles”. Here, we suggest that caution should be taken in calling these principles Darwinian because of the important role played by reticulate evolutionary mechanisms and processes in also bringing about these phenomena. Reticulate mechanisms and processes include symbiosis, symbiogenesis, lateral gene transfer, infective heredity mediated by genetic and organismal mobility, and hybridization. Because the “Darwinian principles” are brought about by both vertical and reticulate evolutionary mechanisms and processes, they should be understood as foundational for a more pluralistic theory of evolution, one that surpasses the classic scope of the Modern and the Neo-Darwinian Synthesis. Reticulate evolution moreover demonstrates that what conventional (Neo-)Darwinian theories treat as intra-species features of evolution frequently involve reticulate interactions between organisms from very different taxonomic categories. Variation, adaptation, heredity and fitness, constraints and affordances, speciation, and extinction therefore cannot be understood as “traits” or “properties” of genes, organisms, species, or ecosystems because the phenomena are irreducible to specific units and levels of an evolutionary hierarchy. Instead, these general principles of evolution need to be understood as common goods that come about through interactions between different units and levels of evolutionary hierarchies, and they are exherent rather than inherent properties of individuals.