We argue that ecology in general and biodiversity and ecosystem function research in particular need an understanding of functions which is both ahistorical and evolutionarily grounded. A natural candidate in this context is Bigelow and Pargetter’s evolutionary forward-looking account which, like the causal role account, assigns functions to parts of integrated systems regardless of their past history, but supplements this with an evolutionary dimension that relates functions to their bearers’ ability to thrive and perpetuate themselves. While Bigelow and Pargetter’s account (...) focused on functional organization at the level of organisms, we argue that such an account can be extended to functional organization at the community and ecosystem levels in a way that broadens the scope of the reconciliation between ecosystem ecology and evolutionary biology envisioned by many BEF researchers. By linking an evolutionary forward-looking account of functions to the persistence-based understanding of evolution defended by Bouchard and others, and to the theoretical research on complex adaptive systems, we argue that ecosystems, by forming more or less resilient assemblages, can evolve even while they do not reproduce and form lineages. We thus propose a Persistence Enhancing Propensity account of role functions in ecology to account for this overlap of evolutionary and ecological processes. (shrink)

Microbes and microbiology are seldom encountered in philosophical accounts of the life sciences. Although microbiology is a well-established science and microbes the basis of life on this planet, neither the organisms nor the science have been seen as philosophically significant. This book will change that. It fills a major gap in the philosophy of biology by examining central philosophical issues in microbiology. Topics are drawn from evolutionary microbiology, microbial ecology, and microbial classification. These discussions are aimed at philosophers and scientists (...) who wish to gain insight into the basic philosophical issues of microbiology. (shrink)

Holobionts are multicellular eukaryotes with multiple species of persistent symbionts. They are not individuals in the genetic sense— composed of and regulated by the same genome—but they are anatomical, physiological, developmental, immunological, and evolutionary units, evolved from a shared relationship between different species. We argue that many of the interactions between human and microbiota symbionts and the reproductive process of a new holobiont are best understood as instances of reciprocal scaffolding of developmental processes and mutual construction of developmental, ecological, and (...) evolutionary niches. Our examples show that mother, fetus, and different symbiotic microbial communities induce or constitute conditions for the development and reproduction of one another. These include the direct induction of maternal or fetus physiological changes, the restructuring of ecological relations between communities, and evolutionary selection against undesirable competitors. The mutual scaffolding and niche constructing processes start early—prior to amniotic rupture. We are evolutionarily, physiologically, and developmentally integrated holobiont systems, strung together through mutual reliance and mutual construction. Bringing the processes of niche construction and developmental scaffolding together to interpret holobiont birth conceptually scaffolds two new directions for research: in niche construction, identifying the evolutionary implications of organisms actively constructing multiple overlapping niches and scaffolds, and in Evolutionary Developmental Biology, characterizing evolutionary and ecological processes as developmental causes. (shrink)

Among mycologists, questions persist about what entities should be treated as the fundamental units of fungal populations. This article articulates a coherent view about populations of heterokaryotic fungi and the individuals that comprise them. Using Godfrey-Smith’s minimal concept of a Darwinian population, I argue that entities at two levels of the biological hierarchy satisfy the minimal concept in heterokaryotic fungi: mycelia and nuclei. I provide a preliminary answer to the question of how to understand the relation between these two populations. (...) This article contributes to discussions about the nature of biological individuality, organismality, and evolutionary transitions. (shrink)

There are two ways evolution by natural selection is conceptualized in the literature. One provides a ‘recipe’ for ENS incorporating three ingredients: variation, differences in fitness, and heritability. The other provides formal equations of evolutionary change and partitions out selection from other causes of evolutionary changes such as transmission biases or drift. When comparing the two approaches there seems to be a tension around the concept of heritability. A recent claim has been made that the recipe approach is flawed and (...) should be abandoned. In this article, I show that the tension is only a superficial one. If one uses a concept of heritability strictly in line with the formal equations of evolutionary change, the recipe approach keeps its validity and generality. To demonstrate that the intuitive concept of heritability is not a general one, I use one formulation of the Price equation formulated by Okasha, show that the concept of heritability in his formulation incorporates both the intuitive notion of heritability as a measure of similarity between parent and offspring characters, and a measure of persistence. I advocate for persistence to be incorporated in the concept of heritability used in recipes for ENS in the same way heredity is, show that this is readily attainable and thereby dissolve any point of tension concerning heritability between the recipe and the analytical approach to ENS. 1 Introduction2 Heritability in the Price Equation2.1 Different approaches to heredity and heritability2.2 Heritability: From recipes to the Price equation3 A Problem for the Recipes?4 Reinterpreting Heritability for Recipes5 Conclusion Appendix. (shrink)

A recent development in biology has been the growing acceptance that holobionts, entities comprised of symbiotic microbes and their host organisms, are widespread in nature. There is agreement that holobionts are evolved outcomes, but disagreement on how to characterize the operation of natural selection on them. The aim of this paper is to articulate the contours of the disagreement. I explain how two distinct foundational accounts of the process of natural selection give rise to competing views about evolutionary individuality.

For evolution by natural selection to occur it is classically admitted that the three ingredients of variation, difference in fitness and heredity are necessary and sufficient. In this paper, I show using simple individual-based models, that evolution by natural selection can occur in populations of entities in which neither heredity nor reproduction are present. Furthermore, I demonstrate by complexifying these models that both reproduction and heredity are predictable Darwinian products (i.e. complex adaptations) of populations initially lacking these two properties but (...) in which new variation is introduced via mutations. Later on, I show that replicators are not necessary for evolution by natural selection, but rather the ultimate product of such processes of adaptation. Finally, I assess the value of these models in three relevant domains for Darwinian evolution. (shrink)

This paper examines David Hull’s and Peter Godfrey-Smith’s accounts of biological individuality using the case of biofilms. Biofilms fail standard criteria for individuality, such as having reproductive bottlenecks and forming parent-offspring lineages. Nevertheless, biofilms are good candidates for individuals. The nature of biofilms shows that Godfrey-Smith’s account of individuality, with its reliance on reproduction, is too restrictive. Hull’s interactor notion of individuality better captures biofilms, and we argue that it offers a better account of biological individuality. However, Hull’s notion of (...) interactor needs more precision. We suggest some ways to make Hull’s notion of interactor and his account of individuality more precise. Generally, we maintain that biofilms are a good test case for theories of individuality, and a careful examination of biofilms furthers our understanding of biological individuality. (shrink)

This paper aims to illustrate one of the primary goals of the philosophy of biology⎯namely, the examination of central concepts in biological theory and practice⎯through an analysis of the concepts of population and metapopulation in evolutionary biology and ecology. I will first provide a brief background for my analysis, followed by a characterization of my proposed concepts: the causal interactionist concepts of population and metapopulation. I will then illustrate how the concepts apply to six cases that differ in their population (...) structure; this analysis will also serve to flesh out and defend the concepts a bit more. Finally, I will respond to some possible questions that my analysis may have raised and then conclude briefly. (shrink)

Following Wallace’s suggestion, Darwin framed his theory using Spencer’s expression “survival of the fittest”. Since then, fitness occupies a significant place in the conventional understanding of Darwinism, even though the explicit meaning of the term ‘fitness’ is rarely stated. In this paper I examine some of the different roles that fitness has played in the development of the theory. Whereas the meaning of fitness was originally understood in ecological terms, it took a statistical turn in terms of reproductive success throughout (...) the 20th Century. This has lead to the ever-increasing importance of sexually reproducing organisms and the populations they compose in evolutionary explanations. I will argue that, moving forward, evolutionary theory should look back at its ecological roots in order to be more inclusive in the type of systems it examines. Many biological systems can only be satisfactorily accounted for by offering a non-reproductive account of fitness. This argument will be made by examining biological systems with very small or transient population structures. I argue this has significant consequences for how we define Darwinism, increasing the significance of survival over that of reproduction. (shrink)

In the six decades since the publication of Julian Huxley's Evolution: The Modern Synthesis, spectacular empirical advances in the biological sciences have been accompanied by equally significant developments within the core theoretical framework of the discipline. As a result, evolutionary theory today includes concepts and even entire new fields that were not part of the foundational structure of the Modern Synthesis. In this volume, sixteen leading evolutionary biologists and philosophers of science survey the conceptual changes that have emerged since Huxley's (...) landmark publication, not only in such traditional domains of evolutionary biology as quantitative genetics and paleontology but also in such new fields of research as genomics and EvoDevo. Most of the contributors to Evolution—The Extended Synthesis accept many of the tenets of the classical framework but want to relax some of its assumptions and introduce significant conceptual augmentations of the basic Modern Synthesis structure—just as the architects of the Modern Synthesis themselves expanded and modulated previous versions of Darwinism. This continuing revision of a theoretical edifice the foundations of which were laid in the middle of the nineteenth century—the reexamination of old ideas, proposals of new ones, and the synthesis of the most suitable—shows us how science works, and how scientists have painstakingly built a solid set of explanations for what Darwin called the "grandeur" of life. (shrink)

Does natural selection act primarily on individual organisms, on groups, on genes, or on whole species? The question of levels of selection - on which biologists and philosophers have long disagreed - is central to evolutionary theory and to the philosophy of biology. Samir Okasha's comprehensive analysis gives a clear account of the philosophical issues at stake in the current debate.

The Nature of Selection is a straightforward, self-contained introduction to philosophical and biological problems in evolutionary theory. It presents a powerful analysis of the evolutionary concepts of natural selection, fitness, and adaptation and clarifies controversial issues concerning altruism, group selection, and the idea that organisms are survival machines built for the good of the genes that inhabit them. "Sober's is the answering philosophical voice, the voice of a first-rate philosopher and a knowledgeable student of contemporary evolutionary theory. His book merits (...) broad attention among both communities. It should also inspire others to continue the conversation."-Philip Kitcher, Nature "Elliott Sober has made extraordinarily important contributions to our understanding of biological problems in evolutionary biology and causality. The Nature of Selection is a major contribution to understanding epistemological problems in evolutionary theory. I predict that it will have a long lasting place in the literature."-Richard C. Lewontin. (shrink)

Philosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy (...) of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations. (shrink)

Biological species have been treated traditionally as spatiotemporally unrestricted classes. If they are to perform the function which they do in the evolutionary process, they must be spatiotemporally localized individuals, historical entities. Reinterpreting biological species as historical entities solves several important anomalies in biology, in philosophy of biology, and within philosophy itself. It also has important implications for any attempt to present an "evolutionary" analysis of science and for sciences such as anthropology which are devoted to the study of single (...) species. (shrink)

Developmental systems theory (DST) expands the unit of replication from genes to whole systems of developmental resources, which DST interprets in terms of cycling developmental processes. Expansion seems required by DST's argument against privileging genes in evolutionary and developmental explanations of organic traits. DST and the expanded replicator brook no distinction between biological and cultural evolution. However, by endorsing a single expanded unit of inheritance and leaving the classical molecular notion of gene intact, DST achieves only a nominal reunification of (...) heredity and development. I argue that an alternative conceptualization of inheritance denies the classical opposition of genetics and development while avoiding the singularity inherent in the replicator concept. It also yields a new unit--the reproducer--which genuinely integrates genetic and developmental perspectives. The reproducer concept articulates the non-separability of "genetic" and "developmental" roles in units of heredity, development, and evolution. DST reformulated in terms of reproducers rather than replicators preserves an empirically interesting distinction between cultural and biological evolution. (shrink)

This paper briefly describes process metaphysics, and argues that it is better suited for describing life than the more standard thing, or substance, metaphysics. It then explores the implications of process metaphysics for conceptualizing evolution. After explaining what it is for an organism to be a process, the paper takes up the Hull/Ghiselin thesis of species as individuals and explores the conditions under which a species or lineage could constitute an individual process. It is argued that only sexual species satisfy (...) these conditions, and that within sexual species the degree of organization varies. This, in turn, has important implications for species' evolvability. One important moral is that evolution will work differently in different biological domains. (shrink)

Heritability is routinely interpreted causally. Yet, what such an interpretation amounts to is often unclear. Here, I provide a causal interpretation of this concept in terms of range of causal influence, one of several causal dimensions proposed within the interventionist account of causation. An information-theoretic measure of range of causal influence has recently been put forward in the literature. Starting from this formalization and relying upon Woodward’s analysis, I show that an important problem associated with interpreting heritability causally, namely the (...) locality problem, amounts, at least partly, to a low invariance and low stability between the genotype/environment and the phenotype of individuals. In light of this, I plead for a causal interpretation of heritability that takes the notions of Woodward’s invariance and stability into consideration. In doing so, I defuse naive causal interpretations of heritability. (shrink)

Holobionts, consisting of a host and diverse microbial symbionts, function as distinct biological entities anatomically, metabolically, immunologically, and developmentally. Symbionts can be transmitted from parent to offspring by a variety of vertical and horizontal methods. Holobionts can be considered levels of selection in evolution because they are well-defined interactors, replicators/reproducers, and manifestors of adaptation. An initial mathematical model is presented to help understand how holobionts evolve. The model offered combines the processes of horizontal symbiont transfer, within-host symbiont proliferation, vertical symbiont (...) transmission, and holobiont selection. The model offers equations for the population dynamics and evolution of holobionts whose hologenomes differ in gene copy number, not in allelic or loci identity. The model may readily be extended to include variation among holobionts in the gene identities of both symbionts and host. (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.

It is now widely accepted that microorganisms play many important roles in the lives of plants and animals. Every macroorganism has been shaped in some way by microorganisms. The recognition of the ubiquity and importance of microorganisms has led some to argue for a revolution in how we understand biological individuality and the primary units of natural selection. The term “holobiont” was introduced as a name for the biological unit made up by a host and all of its associated microorganisms, (...) and much of this new debate about biological individuality has focused on whether holobionts are integrated individuals or communities. In this paper, I show how parts of the holobiont can span both characterizations. I argue that most holobionts share more affinities with communities than they do with organisms, and that, except for maybe in rare cases, holobionts do not meet the criteria for being organisms, evolutionary individuals, or units of selection. (shrink)

Both biologists and philosophers often make use of simple verbal formulations of necessary and sufficient conditions for evolution by natural selection (ENS). Such summaries go back to Darwin's Origin of Species (especially the "Recapitulation"), but recent ones are more compact.1 Perhaps the most commonly cited formulation is due to Lewontin.2 These summaries tend to have three or four conditions, where the core requirement is a combination of variation, heredity, and fitness differences. The summaries are employed in several ways. First, they (...) are often used in pedagogical contexts, and in showing the coherence of evolutionary theory in response to attacks from outside biology. Second, they are important in discussions of extensions of evolutionary principles to new domains, such as cultural change. The summaries also have intrinsic scientific and philosophical interest as attempts to capture some core principles of evolutionary theory in a highly concise way. Despite their prominence, both the proper formulation and status of these summaries are unclear. Standard formulations are subject to counterexamples, and their relations to formal models of evolutionary change are not straightforward. Here I look closely at these verbal summaries, and at how they relate to formal models. Are the summaries merely rough approximations that have no theoretical role of their own? Perhaps they could operate as theoretical statements in Darwin's time, but have now been superseded by more exact treatments. (shrink)

Biologists studying ecology and evolution use the term “population” in many different ways. Yet little philosophical analysis of the concept has been done, either by biologists or philosophers, in contrast to the voluminous literature on the concept of “species.” This is in spite of the fact that “population” is arguably a far more central concept in ecological and evolutionary studies than “species” is. The fact that such a central concept has been employed in so many different ways is potentially problematic (...) for the reason that inconsistent usages (especially when the usage has not been made explicit) might lead to false controversies in which disputants are simply talking past one another. However, the inconsistent usages are not the only, or even the most important reason to examine the concept. If any set of organisms is legitimately called a “population,” selection and drift processes become purely arbitrary, too. Moreover, key ecological variables, such as abundance and distribution, depend on a nonarbitrary way of identifying populations. I sketch the beginnings of a population concept, drawing inspiration from the Ghiselin-Hull individuality thesis, and show why some alternative approaches are nonstarters. (shrink)

The book presents a new way of understanding Darwinism and evolution by natural selection, combining work in biology, philosophy, and other fields.

Recent discussions in the philosophy of biology have brought into question some fundamental assumptions regarding evolutionary processes, natural selection in particular. Some authors argue that natural selection is nothing but a population-level, statistical consequence of lower-level events (Matthen and Ariew [2002]; Walsh et al. [2002]). On this view, natural selection itself does not involve forces. Other authors reject this purely statistical, population-level account for an individual-level, causal account of natural selection (Bouchard and Rosenberg [2004]). I argue that each of these (...) positions is right in one way, but wrong in another; natural selection indeed takes place at the level of populations, but it is a causal process nonetheless. (shrink)

We argue that a fashionable interpretation of the theory of natural selection as a claim exclusively about populations is mistaken. The interpretation rests on adopting an analysis of fitness as a probabilistic propensity which cannot be substantiated, draws parallels with thermodynamics which are without foundations, and fails to do justice to the fundamental distinction between drift and selection. This distinction requires a notion of fitness as a pairwise comparison between individuals taken two at a time, and so vitiates the interpretation (...) of the theory as one about populations exclusively. (shrink)

argue that natural selection does not explain the genotypic arid phenotypic properties of individuals. On this view, natural selection explains the adaptedness of individuals, not by explaining why the individuals that exist have the adaptations they do, but rather by explaining why the individuals that exist are the ones with those adaptations. This paper argues that this ‘Negative’ view of natural selection ignores the fact that natural selection is a cumulative selection process. So understood, it explains how the genetic sequences (...) that individuals inherit and that are responsible for their complex (and co-adapted) adaptations first arose in the gene-pool. (shrink)

The world's foremost geneticist surveys the major developments in what is emerging as the most important single area of scientific inquiry in the twentieth century: biological theory of evolution.

College of Medicine, University of South Alabama Mobile, AL 36688-0002, USA wbp501{at}jaguar1.usouthal.edu ' + u + '@' + d + ' '//--> Abstract Recent work in viral genomics has shown that bacteriophages exhibit a high degree of mosaicism, which is most likely due to a long history of prolific horizontal gene transfer (HGT). Given these findings, we argue that each of the most plausible attempts to properly classify bacteriophages into distinct species fail. Mayr's biological species concept fails because there is (...) no useful viral analog to sexual reproduction. Phenetic species concepts fail because they obscure the mosaicism and the rich reticulated viral histories. Phylogenetic species concepts, even when extended to take into account reticulation, fail because there is no non-arbitrary distinction between recombination events that create a new viral species and those that do not. There is good reason to think that bacteriophages, arguably the Earth's most abundant biological agent, evolve without forming species. Introduction The Biology of Viruses 2.1 Bacteriophage life cycles 2.2 Mechanisms of HGT The Species Problem and Species Concepts 3.1 Phenetic species concepts 3.2 The biological species concept 3.3 Phylogenetic species concepts 3.4 The ecological species concept 3.5 Homeostatic property cluster species Viruses and Species Taxonomy Reticular Phylogenies Conclusion CiteULike Connotea Del.icio.us What's this? (shrink)

At least below the level of species, biological populations are not mind‐independent objects that scientists discover. Rather, biological populations are pragmatically constructed as objects of investigation according to the aims, interests, and values that inform particular research contexts. The relations among organisms that are constitutive of population‐level phenomena (e.g., mating propensity, genealogy, and competition) occur as matters of degree and so give rise to statistically defined open‐ended biological systems. These systems are rendered discrete units to satisfy practical needs and theoretical (...) preferences associated with specific contexts of investigation. While it may be possible to defend a realist position regarding biological relations among organisms, biological populations are “made” when contextual features determine which kinds and degrees of relations to privilege over others, and so how to bound genes in space and time. Consequently, the objectivity of population‐based approaches to species genome diversity cannot rest in the mind‐independence of populations themselves. (shrink)

Ecological fitness has been suggested to provide a unifying definition of fitness. However, a metric for this notion of fitness was in most cases unavailable except by proxy with differential reproductive success. In this article, I show how differential persistence of lineages can be used as a way to assess ecological fitness. This view is inspired by a better understanding of the evolution of some clonal plants, colonial organisms, and ecosystems. Differential persistence shows the limitation of an ensemblist noncausal understanding (...) of evolution. Causal explanations are necessary to understand the evolution by natural selection of these biological systems. †To contact the author write to: Department of Philosophy, University of Montreal, P.O. Box 6128, Station Centre‐Ville, Montreal, Quebec, H3C 3J7 Canada; e‐mail: [email protected]. (shrink)

The thesis that natural selection explains the frequencies of traits in populations, but not why individual organisms have the traits tehy do, is here defended and elaborated. A general concept of ‘distributive explanation’ is discussed.

For a population to undergo evolution by natural selection, it is assumed that the constituents of the population form parent-offspring lineages, that is, that they must reproduce. I challenge this assumption by dividing the notion of reproduction into two subprocesses, that is, multiplication and inheritance, that produce parent-offspring lineages between the parts of a population, and I show that their population-level roles, generation and memory, respectively, can be effected by processes that do not rely on such local-level lineages. I further (...) argue that these two population-level processes, not local parent-offspring lineages, are necessary conditions for a population to undergo Darwinian evolution. (shrink)

While evolutionary thinking is increasingly becoming popular in fields of investigation outside the biological sciences, it remains unclear how helpful it is there and whether it actually yields good explanations of the phenomena under study. Here we examine the ontology of a recent approach to applying evolutionary thinking outside biology, the generalized Darwinism approach proposed by Geoffrey Hodgson and Thorbjørn Knudsen. We examine the ontology of populations in biology and in GD, and argue that biological evolutionary theory sets ontological criteria (...) that GD fails to meet. We suggest two options to revise the population concept in GD: reformulating the concept in terms of inheritance and reproduction such that it comes to pick out individuals similar to evolving populations, or trying to build an adequate population concept on a principle of differential retention instead of differential reproduction. 1 Introduction2 Generalized Darwinism2.1 What is generalized Darwinism?2.2 Darwinian principles3 The Ontology of Generalized Darwinism: What Are Populations?3.1 The population concept of generalized Darwinism3.2 The population concept in evolutionary theory4 Locating Evolving Systems in Generalized Darwinism5 Conclusion. (shrink)

In much of the discourse of evolutionary theory, reproduction is treated as an autonomous function of the individual organism — even in discussions of sexually reproducing organisms. In this paper, I examine some of the functions and consequences of such manifestly peculiar language. In particular, I suggest that it provides crucial support for the central project of evolutionary theory — namely that of locating causal efficacy in intrinsic properties of the individual organism. Furthermore, I argue that the language of individual (...) reproduction is maintained by certain methodological conventions that both obscure many of the problems it generates and serve to actively impede attempts to redress those difficulties that can be identified. Finally, I suggest that inclusion of the complexities introduced by sexual reproduction — in both language and methodology — may radically undermine the individualist focus of evolutionary theory. (shrink)

One of intuitions driving the acceptance of a neat structured tree of life is the assumption that organisms and the lineages they form have somewhat stable spatial and temporal boundaries. The phenomenon of symbiosis shows us that such ‘fixist’ assumptions does not correspond to how the natural world actually works. The implications of lateral gene transfer (LGT) have been discussed elsewhere; I wish to stress a related point. I will focus on lateral function transfer (LFT) and will argue, using examples (...) of what many would call ‘superorganisms’, that the emergence of symbiotic individuals revives the importance of functional and adaptationist thinking in how we conceptualize the lineages of biological individuals. The consequence of the argument is that, if we really want to hold onto tree of life thinking, we had better accept that new saplings appear and disappear all the time. (shrink)

On the classical account of evolution by natural selection found in Lewontin and many subsequent authors, ENS is conceived as involving three key ingredients: phenotypic variation, fitness differences, and heredity. Through the analysis of three problem cases involving heredity, I argue that the classical conception is substantially flawed, showing that heredity is not required for selection. I consider further problems with the classical account of ENS arising from conflations between three distinct senses of the central concept of ‘fitness’ and offer (...) an alternative to the classical conception of ENS involving the interaction of distinct evolutionary mechanisms. (shrink)