In the half century since the formulation of the prokaryote : eukaryote dichotomy, many authors have proposed that the former evolved from something resembling the latter, in defiance of common (and possibly common sense) views. In such ‘eukaryotes first’ (EF) scenarios, the last universal common ancestor is imagined to have possessed significantly many of the complex characteristics of contemporary eukaryotes, as relics of an earlier ‘progenotic’ period or RNAworld. Bacteria and Archaea thus must have lost these complex features secondarily, through (...) ‘streamlining’. If the canonical three-domain tree in which Archaea and Eukarya are sisters is accepted, EF entails that Bacteria and Archaea are convergently prokaryotic.We ask what this means and how it might be tested. (shrink)

Reproduction is central to biology and evolution. Standard concepts of reproduction are drawn from animals. Nonstandard examples of reproduction can be found in unicellular eukaryotes that distribute their reproductive strategies across multiple generations, and in mutualistic systems that combine different modes of reproduction across multiple lineages. Examining multigenerational and multilineal reproducers and how they align fitness has implications for conceptualizing units of evolution.

Constructive Neutral Evolution is an evolutionary mechanism that can explain much molecular inter-dependence and organismal complexity without assuming positive selection favoring such dependency or complexity, either directly or as a byproduct of adaptation. It differs from but complements other non-selective explanations for complexity, such as genetic drift and the Zero Force Evolutionary Law, by being ratchet-like in character. With CNE, purifying selection maintains dependencies or complexities that were neutrally evolved. Preliminary treatments use it to explain specific genetic and molecular structures (...) or processes, such as retained gene duplications, the spliceosome, and RNA editing. Here we aim to expand the scope of such explanation beyond the molecular level, integrating CNE with Multi-Level Selection theory, and arguing that several popular higher-level selection scenarios are in fact instances of CNE. Suitably contextualized, CNE occurs at any level in the biological hierarchy at which natural selection as normally construed occurs. As examples, we focus on modularity in protein–protein interaction networks or “interactomes,” the origin of eukaryotic cells and the evolution of co-dependence in microbial communities—a variant of the “Black Queen Hypothesis” which we call the “Gray Queen Hypothesis”. (shrink)

In this article we focus on the emergence of biological individuality by association, trying to formulate some theoretical conditions to think about the process of collective individualization. The starting point of our analysis is the notion of “major evolutionary transition.” A major evolutionary transition is the result of the integration of a multiplicity of initially independent biological entities that, by managing to organize their interactions, become a collective of components having an identity oriented towards a common goal. When biological organisms (...) are concerned, a major transition corresponds to a phenomenon of fusion between them. We shall argue that the emergence of a new biological level of individuality implies the establishment of constitutive relationships between individuals that change their status as autonomous entities. As a result, the emergence of a new type of entity in the living world implies that individuals enter into relationships that intrinsically transform them, a transformation sufficient for a “whole” to become a “part” that forms another “whole”, that is, a new level of organismality. (shrink)

Behavioral genetics and cultural evolution have both revolutionized our understanding of human behavior – largely independent of each other. Here, we reconcile these two fields under a dual inheritance framework, offering a more nuanced understanding of the interaction between genes and culture. Going beyond typical analyses of gene–environment interactions, we describe the cultural dynamics that shape these interactions by shaping the environment and population structure. A cultural evolutionary approach can explain, for example, how factors such as rates of innovation and (...) diffusion, density of cultural subgroups, and tolerance for behavioral diversity impact heritability estimates, thus yielding predictions for different social contexts. Moreover, when cumulative culture functionally overlaps with genes, genetic effects become masked, unmasked, or even reversed, and the causal effects of an identified gene become confounded with features of the cultural environment. The manner of confounding is specific to a particular society at a particular time, but a WEIRD (western, educated, industrialized, rich, and democratic) sampling problem obscures this boundedness. Cultural evolutionary dynamics are typically missing from models of gene-to-phenotype causality, hindering generalizability of genetic effects across societies and across time. We lay out a reconciled framework and use it to predict the ways in which heritability should differ between societies, between socioeconomic levels, and other groupings within some societies but not others, and over the life course. An integrated cultural evolutionary behavioral genetic approach cuts through the nature–nurture debate and helps resolve controversies in topics such as IQ. (shrink)

Protistology, and evolutionary protistology in particular, is experiencing a golden research era. It is an extended one that can be dated back to the 1970s, which is when the molecular rebirth of microbial phylogeny began in earnest. John Archibald, a professor of evolutionary microbiology at Dalhousie University, focuses on the beautiful story of endosymbiosis in his book, John Archibald, One Plus One Equals One: Symbiosis and the Origin of Complex Life. However, this historical narrative could be treated as synecdochal of (...) how the molecular revolution has changed evolutionary biology forever, and that is how Archibald has structured his book. I will address the encompassing theme of molecular methods in detail, but also pay careful attention to the endosymbiosis thread in its own right. (shrink)