The propensity interpretation of fitness (PIF) is commonly taken to be subject to a set of simple counterexamples. We argue that three of the most important of these are not counterexamples to the PIF itself, but only to the traditional mathematical model of this propensity: fitness as expected number of offspring. They fail to demonstrate that a new mathematical model of the PIF could not succeed where this older model fails. We then propose a new formalization of the (...) PIF that avoids these (and other) counterexamples. By producing a counterexample-free model of the PIF, we call into question one of the primary motivations for adopting the statisticalist interpretation of fitness. In addition, this new model has the benefit of being more closely allied with contemporary mathematical biology than the traditional model of the PIF. (shrink)
A philosophical discussion of conceptual and theoretical issues raised by the scientific use of the term ‘fitness’ to describe a property of evolving systems.
Fitness plays many roles throughout evolutionary theory, from a measure of populations in the wild to a central element in abstract theoretical presentations of natural selection. It has thus been the subject of an extensive philosophical literature, which has primarily centered on the way to understand the relationship between fitness values and reproductive outcomes. If fitness is a probabilistic or statistical quantity, how is it to be defined in general theoretical contexts? How can it be measured? Can (...) a single conceptual model for fitness be offered that applies in all biological cases, or must fitness measures be case-specific? Philosophers have explored these questions over the last several decades, largely in the context of an influential definition of fitness proposed in the late 1970s: the propensity interpretation. This interpretation as first described undeniably suffers from significant difficulties, and debate regarding the tenability of amendments and alternatives to it remains unsettled. (shrink)
Matthen (Philos Sci 76(4):464–487, 2009) argues that explanations of evolutionary change that appeal to natural selection are statistically abstractive explanations, explanations that ignore some possible explanatory partitions that in fact impact the outcome. This recognition highlights a difficulty with making selective analyses fully rigorous. Natural selection is not about the details of what happens to any particular organism, nor, by extension, to the details of what happens in any particular population. Since selective accounts focus on tendencies, those factors that impact (...) the actual outcomes but do not impact the tendencies must be excluded. So, in order to properly exclude the factors irrelevant to selection, the relevant factors must be identified, and physical processes, environments, and populations individuated on the basis of being relevantly similar for the purposes of selective accounts. Natural selection, on this view, becomes in part a measure of the robustness of particular kinds of outcomes given variations over some kinds of inputs. (shrink)
How do fitness and natural selection relate to other evolutionary factors like architectural constraint, mode of reproduction, and drift? In one way of thinking, drawn from Newtonian dynamics, fitness is one force driving evolutionary change and added to other factors. In another, drawn from statistical thermodynamics, it is a statistical trend that manifests itself in natural selection histories. It is argued that the first model is incoherent, the second appropriate; a hierarchical realization model is proposed as a basis (...) for a statistical treatment. It emerges that natural selection does not cause evolution; it just is evolution. The theory incorporates relations of statistical correlation, but not the kind of causation found in fundamental physical processes. (shrink)
The concept of "fitness" is a notion of central importance to evolutionary theory. Yet the interpretation of this concept and its role in explanations of evolutionary phenomena have remained obscure. We provide a propensity interpretation of fitness, which we argue captures the intended reference of this term as it is used by evolutionary theorists. Using the propensity interpretation of fitness, we provide a Hempelian reconstruction of explanations of evolutionary phenomena, and we show why charges of circularity which (...) have been levelled against explanations in evolutionary theory are mistaken. Finally, we provide a definition of natural selection which follows from the propensity interpretation of fitness, and which handles all the types of selection discussed by biologists, thus improving on extant definitions. (shrink)
The GDC’s recent third edition (interim) of The First Five Years places renewed emphasis on the place of professionalism in the undergraduate dental curriculum. This paper provides a brief analysis of the concepts of ethics, professionalism and fitness to practice, and an examination of the GDC’s First Five Years and Standards for Dental Professionals guidance, as well as providing an insight into the innovative ethics strand of the BDS course at the University of Glasgow. It emerges that GDC guidance (...) is flawed inasmuch as it advocates a virtue-based approach to ethics and professionalism, and fails to distinguish clearly between these two concepts. (shrink)
In evolutionary biology changes in population structure are explained by citing trait fitness distribution. I distinguish three interpretations of fitness explanations—the Two‐Factor Model, the Single‐Factor Model, and the Statistical Interpretation—and argue for the last of these. These interpretations differ in their degrees of causal commitment. The first two hold that trait fitness distribution causes population change. Trait fitness explanations, according to these interpretations, are causal explanations. The last maintains that trait fitness distribution correlates with population (...) change but does not cause it. My defense of the Statistical Interpretation relies on a distinctive feature of causation. Causes conform to the Sure Thing Principle. Trait fitness distributions, I argue, do not. *Received July 2009; revised October 2009. †To contact the author, please write to: Department of Philosophy/Institute for the History, Philosophy of Science and Technology, University of Toronto, Victoria College, 91 Charles Street West, Toronto, ON M5S 1K7, Canada; e‐mail: denis.walsh@utoronto.ca. (shrink)
The concept of fitness began its career in biology long before evolutionary theory was mathematized. Fitness was used to describe an organism’s vigor, or the degree to which organisms “fit” into their environments. An organism’s success in avoiding predators and in building a nest obviously contribute to its fitness and to the fitness of its offspring, but the peacock’s gaudy tail seemed to be in an entirely different line of work. Fitness, as a term in (...) ordinary language (as in “physical fitness”) and in its original biological meaning, applied to the survival of an organism and its offspring, not to sheer reproductive output (Paul ////; Cronin 1991). Darwin’s separation of natural from sexual selection may sound odd from a modern perspective, but it made sense from this earlier point of view. (shrink)
The central point of this essay is to demonstrate the incommensurability of ‘Darwinian fitness’ with the numeric values associated with reproductive rates used in population genetics. While sometimes both are called ‘fitness’, they are distinct concepts coming from distinct explanatory schemes. Further, we try to outline a possible answer to the following question: from the natural properties of organisms and a knowledge of their environment, can we construct an algorithm for a particular kind of organismic life-history pattern that (...) itself will allow us to predict whether a type in the population will increase or decrease relative to other types? Introduction Darwinian fitness Reproductive fitness and genetical models of evolution The models of reproductive fitness 4.1 The Standard Viability Model 4.2 Frequency-dependent selection 4.3 Fertility models 4.4 Overlapping generations Fitness as outcome 5.1 Fitness as actual increase in type 5.2 Fitness as expected increase in type 5.2.1 Expected increase within a generation 5.2.2 Expected increase between generations 5.2.3 Postponed reproductive fitness effects The book-keeping problem Conclusion. (shrink)
It’s recently been argued that biological fitness can’t change over the course of an organism’s life as a result of organisms’ behaviors. However, some characterizations of biological function and biological altruism tacitly or explicitly assume that an effect of a trait can change an organism’s fitness. In the first part of the paper, I explain that the core idea of changing fitness can be understood in terms of conditional probabilities defined over sequences of events in an organism’s (...) life. The result is a notion of “conditional fitness” which is static but which captures intuitions about apparent behavioral effects on fitness. The second part of the paper investigates the possibility of providing a systematic foundation for conditional fitness in terms of spaces of sequences of states of an organism and its environment. I argue that the resulting “organism–environment history conception” helps unify diverse biological perspectives, and may provide part of a metaphysics of natural selection. (shrink)
Recently advocates of the propensity interpretation of fitness have turned critics. To accommodate examples from the population genetics literature they conclude that fitness is better defined broadly as a family of propensities rather than the propensity to contribute descendants to some future generation. We argue that the propensity theorists have misunderstood the deeper ramifications of the examples they cite. These examples demonstrate why there are factors outside of propensities that determine fitness. We go on to argue for (...) the more general thesis that no account of fitness can satisfy the desiderata that have motivated the propensity account. (shrink)
Darwin’s explanation of biological speciation in terms of variation and natural selection has revolutionised biological thought. However, while his principle of natural selection, the fitness principle, has shaped biology until the present, its interpretation changed more than once during the almost 150 years of its history. The most striking change of the status of the principle is that, in the middle of the 20th century, it transmutated from an often disputed, groundbreaking insight into a tautology. Moreover, not only the (...) interpretation of the fitness principle, but the whole body of biological knowledge was subjected to significant modifications. In this paper, I relate modifications of the fitness principle to those of the respective body of biological knowledge. This body of knowledge is conceived as a Quinean web of belief. After an exposition of Darwin’s conception of the principle, which equated fitness with adaptedness to the environment, several of its changes are analysed with respect to different webs of biological knowledge. It is concluded that the different interpretations and the reshaping of the fitness principle are rational responses to the modified systems of background knowledge, which saved the coherence of the web of biological knowledge in each single case. (shrink)
In models of multi-level selection, the property of Darwinian fitness is attributed to entities at more than one level of the biological hierarchy, e.g. individuals and groups. However, the relation between individual and group fitness is a controversial matter. Theorists disagree about whether group fitness should always, or ever, be defined as total (or average) individual fitness. This paper tries to shed light on the issue by drawing on work in social choice theory, and pursuing an (...) analogy between fitness and utility. Social choice theorists have long been interested in the relation between individual and social utility, and have identified conditions under which social utility equals total (or average) individual utility. These ideas are used to shed light on the biological problem. (shrink)
ÒThe concept of fitness is,Ó Philip Kitcher says, Òimportant both to informal presentations of evolutionary theory and to the mathematical formulations of [population genetics].Ó1 He is absolutely right. The difficulty is to harmonize these very different ways of understanding its role. In this paper, we examine how natural selection relates to the other explanatory factors invoked by evolutionary theory. We argue that the Òinformal presentationsÓ to which Kitcher alludes give an incoherent account of the relation. A more appropriate model (...) is drawn from the statistical conceptual framework of population genetics. We argue that this model demands a far-reaching revision of some widely accepted notions of causal relations in evolution. (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: f.bouchard@umontreal.ca. (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)
Recent philosophical discussions have failed to clarify the roles of the concept fitness in evolutionary theory. Neither the propensity interpretation of fitness nor the construal of fitness as a primitive theoretical term succeed in explicating the empirical content and explanatory power of the theory of natural selection. By appealing to the structure of simple mathematical models of natural selection, we separate out different contrasts which have tended to confuse discussions of fitness: the distinction between what (...) class='Hi'>fitness is defined as versus what fitness is a function of, the contrast between adaptedness as an overall property of organisms and specific adaptive capacities, the distinction between actual and potential reproductive success, the role of chance versus systematic causal relations, fitness as applied to organisms as opposed to fitness applied to genotype classes, heritable adaptive capacities of genotypes as opposed to relations between genotypes and the environment. We show how failure to distinguish and properly interrelate these different aspects of “fitness” adds confusion to a number of already complex issues concerning evolutionary theory. On the basis of our discussion of these different aspects of “fitness”, we propose a terminology which makes the necessary distinctions. A central result of our analysis is that the concept of fitness as the overall adaptedness of organisms does not enter into the causal structure of evolutionary explanation, at least to the extent that this structure is represented in the mathematical models of natural selection. (shrink)
Philosophers of biology have been absorbed by the problem of defining evolutionary fitness since Darwin made it central to biological explanation. The apparent problem is obvious. Define fitness as some biologists implicitly do, in terms of actual survival and reproduction, and the principle of natural selection turns into an empty tautology: those organisms which survive and reproduce in larger numbers, survive and reproduce in larger numbers. Accordingly, many writers have sought to provide a definition for ‘fitness’ which (...) avoid this outcome. In particular the definition of fitness as a probabilistic propensity has been widely favored.1 Others, recognizing that no definition both correct and complete can actually be provided, have accepted the consequence that the leading principle of the theory is a definitional truth and attempted to mitigate the impact of this outcome for the empirical character of the theory.2 Still others have argued that ‘fitness’ is properly viewed as a term undefined in the theory of natural selection (on the model of mass—a term undefined in Newtonian mechanics).3 But few have contemplated the solution to this problem proposed by Mohan Matthen and André Ariew (hereafter, MA), in.. (shrink)
According to historical theories of biological function, a trait's function is determined by natural selection in the past. I argue that, in addition to historical functions, ahistorical functions ought to be recognized. I propose a theory of biological function which accommodates both. The function of a trait is the way it contributes to fitness and fitness can only be determined relative to a selective regime. Therefore, the function of a trait can only be specified relative to a selective (...) regime. Apart from its desirable pluralism, only this view of relational function can support the function/accident and function/malfunction distinctions commonly thought to be part of the concept of function. Furthermore, only relational function correctly characterizes the explanatory consequences of function attributions in evolutionary biology. (shrink)
We critically examine Denis Walsh’s latest attack on the causalist view of fitness. Relying on Judea Pearl’s Sure-Thing Principle and geneticist John Gillespie’s model for fitness, Walsh has argued that the causal interpretation of fitness results in a reductio. We show that his conclusion only follows from misuse of the models, that is, (1) the disregard of the real biological bearing of the population-size parameter in Gillespie’s model and (2) the confusion of the distinction between ordinary probability (...) and Pearl’s causal probability. Properly understood, the models used by Walsh do not threaten the causalist view of fitness. (shrink)
According to Pigliucci and Kaplan, there is a revolution underway in how we understand fitness landscapes. Recent models suggest that a perennial problem in these landscapes—how to get from one peak across a fitness valley to another peak—is, in fact, non-existent. In this paper I assess the structure and the extent of Pigliucci and Kaplan’s proposed revolution and argue for two points. First, I provide an alternative interpretation of what underwrites this revolution, motivated by some recent work on (...) model-based science. Second, I show that the implications of this revolution need to carefully assessed depending on question being asked, for peak-shifting is not central to all evolutionary questions that fitness landscapes have been used to explore. (shrink)
Hutcheson’s theory of morality shares far more common ground with Clarke’s morality than is generally acknowledged. In fact, Hutcheson’s own view of his innovations in moral theory suggest that he understood moral sense theory more as an elaboration and partial correction to Clarkean fitness theory than as an outright rejection of it. My aim in this paper will be to illuminate what I take to be Hutcheson’s grounds for adopting this attitude toward Clarkean fitness theory. In so doing, (...) I hope to bring to light an otherwise unexpected continuity between moral sense theory and the moral rationalism to which it is usually opposed, and, in so doing, draw attention to the anti-sceptical realism that lies at the heart of both accounts. (shrink)
It has been argued that biological fitness cannot be defined as expected number of offspring in all contexts. Some authors argue that fitness therefore merely satisfies a common schema or that no unified mathematical characterization of fitness is possible. I argue that comparative fitness must be relativized to an evolutionary effect; thus relativized, fitness can be given a unitary mathematical characterization in terms of probabilities of producing offspring and other effects. Such fitnesses will sometimes be (...) defined in terms of probabilities of effects occurring over the long term, but these probabilities nevertheless concern effects occurring over the short term. †To contact the author, please write to: Department of Philosophy, University of Alabama at Birmingham, HB 414A, 900 13th Street South, Birmingham, AL 35294‐1260; e‐mail: mabrams@uab.edu. (shrink)
Recent debate on the nature of probabilities in evolutionary biology has focused largely on the propensity interpretation of fitness (PIF), which defines fitness in terms of a conception of probability known as “propensity”. However, proponents of this conception of fitness have misconceived the role of probability in the constitution of fitness. First, discussions of probability and fitness have almost always focused on organism effect probability, the probability that an organism and its environment cause effects. I (...) argue that much of the probability relevant to fitness must be organism circumstance probability, the probability that an organism encounters particular, detailed circumstances within an environment, circumstances which are not the organism’s effects. Second, I argue in favor of the view that organism effect propensities either don’t exist or are not part of the basis of fitness, because they usually have values close to 0 or 1. More generally, I try to show that it is possible to develop a clearer conception of the role of probability in biological processes than earlier discussions have allowed. (shrink)
The diversity, complexity and adaptation of the biological realm is evident. Until Darwin, the best explanation for these three features of the biological was the conclusion of the “argument from design.” Darwin's theory of natural selection provides an explanation of all three of these features of the biological realm without adverting to some mysterious designing entity. But this explanation's success turns on the meaning of its central explanatory concept, ‘fitness’. Moreover, since Darwinian theory provides the resources for a purely (...) causal account of teleology, wherever it is manifested, its reliance on the concept of ‘fitness’ makes it imperative that conceptual problems threatening the explanatory legitimacy of this notion be solved. (shrink)
Altruism is a central concept in evolutionary biology. Evolutionary biologists still disagree about its meaning (E.O. Wilson 2005; Fletcher et al. 2006; D.S. Wilson 2008; Foster et al. 2006a, b; West et al. 2007a, 2008). Semantic disagreement appears to be quite robust and not easily overcome by attempts at clarification, suggesting that substantive conceptual issues lurk in the background. Briefly, group selection theorists define altruism as any trait that makes altruists losers to selfish traits within groups, and makes groups of (...) altruists fitter than groups of non-altruists. Inclusive fitness theorists reject a definition based on within- and between-group fitness. Traits are altruistic only if they cause a direct and absolute fitness loss to the donor. The latter definition is more restrictive and rejects as cases of altruism behaviors that are accepted by the former. Fletcher and Doebeli (2009) recently proposed a simple, direct and individually based fitness approach, which they claim returns to first principles: carriers of the genotype of interest “must, on average, end up with more net direct fitness benefits than average population members.” This seductively simple proposal uses the concept of assortment to explain how diverse kinds of altruists end up on average with more net fitness than their non-altruistic rivals. In this paper I shall argue that their approach implies a new concept of altruism that contrasts with and improves on the concept of the inclusive fitness approach. (shrink)
The supervenience and multiple realizability of biological properties have been invoked to support a disunified picture of the biological sciences. I argue that supervenience does not capture the relation between fitness and an organism's physical properties. The actual relation is one of causal dependence and is, therefore, amenable to causal explanation. A case from optimality theory is presented and interpreted as a microreductive explanation of fitness difference. Such microreductions can have considerable scope. Implications are discussed for reductive physicalism (...) in evolutionary biology and for the unity of science. (shrink)
The concept of fitness, central to population genetics and to the synthetic theory of evolution, is discussed. After a historical introduction on the origin of this concept, the current meaning of it in population genetics is examined: a cause of the selective process and its quantification. Several difficulties arise for its exact definition. Three adequacy criteria for such a definition are formulated. It is shown that it is impossible to formulate an adequate definition of fitness respecting these criteria. (...) The propensity definition of fitness is presented and rejected. Finally it is argued that fitness is a conceptual device, a useful tool, only for descriptive purposes of selective processes, changing from case to case, and thus devoid of any substantial physical counterpart. Any attempt to its reification is an apport to the metaphysical load evolutionary theory has inherited from Natural Theology. (shrink)
A number of recent discussions have argued that George Price's equationfor representing evolutionary change is a powerful and illuminatingtool, especially in the context of debates about multiple levels ofselection. Our paper dissects Price's equation in detail, and comparesit to another statistical tool: the calculation and comparison ofaverage fitnesses. The relations between Price's equation and equationsfor evolutionary change using average fitness are closer than issometimes supposed. The two approaches achieve a similar kind ofstatistical summary of one generation of change, and (...) they achieve thisvia a similar loss of information about the underlying fitnessstructure. (shrink)
I argue that the propensity interpretation of fitness, properly understood, not only solves the explanatory circularity problem and the mismatch problem, but can also withstand the Pandora’s box full of problems that have been thrown at it. Fitness is the propensity (i.e., probabilistic ability, based on heritable physical traits) for organisms or types of organisms to survive and reproduce in particular environments and in particular populations for a specified number of generations; if greater than one generation, “reproduction” includes (...) descendants of descendants. Fitness values can be described in terms of distributions of propensities to produce varying number of offspring and can be modeled for any number of generations using computer simulations, thus providing both predictive power and a means for comparing the fitness of different phenotypes. Fitness is a causal concept, most notably at the population level, where fitness differences are causally responsible for differences in reproductive success. Relative fitness is ultimately what matters for natural selection. (shrink)
The diversity, complexity and adaptation of the biological realm is evident. Until Darwin, the best explanation for these three features of the biological was the conclusion of the “argument from design.” Darwin's theory of natural selection provides an explanation of all three of these features of the biological realm without adverting to some mysterious designing entity. But this explanation's success turns on the meaning of its central explanatory concept, ‘fitness’. Moreover, since Darwinian theory provides the resources for a purely (...) causal account of teleology, wherever it is manifested, its reliance on the concept of ‘fitness’ makes it imperative that conceptual problems threatening the explanatory legitimacy of this notion be solved. (shrink)
Organisms' environments are thought to play a fundamental role in determining their fitness and hence in natural selection. Existing intuitive conceptions of environment are sufficient for biological practice. I argue, however, that attempts to produce a general characterization of fitness and natural selection are incomplete without the help of general conceptions of what conditions are included in the environment. Thus there is a "problem of the reference environment"—more particularly, problems of specifying principles which pick out those environmental conditions (...) which determine fitness. I distinguish various reference environment problems and propose solutions to some of them. While there has been a limited amount of work on problems concerning what I call "subenvironments", there appears to be no earlier work on problems of what I call the "whole environment". The first solution I propose for a whole environment problem specifies the overall environment for natural selection on a set of biological types present in a population over a specified period of time. The second specifies an environment relevant to extinction of types in a population; this kind of environment is especially relevant to certain kinds of long-term evolution. (shrink)
We claim that much of the confusion associated with the "tautology problem" about survival of the fittest is due to the mistake of attributing fitness to individuals instead of to types. We argue further that the problem itself cannot be solved merely by taking fitness as the aggregate cause of reproductive success. We suggest that a satisfying explanation must center not on logical analysis of the concept of general adaptedness but on the empirical analysis of single adapted traits (...) and their causal relationship to changes in allele frequencies. (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)
Biological fitness is a foundational concept in the theory of natural selection. Natural selection is often defined in terms of fitness differences as “any consistent difference in fitness (i.e., survival and reproduction) among phenotypically different biological entities” (Futuyma 1998, 349). And in Lewontin’s (1970) classic articulation of the theory of natural selection, he lists fitness differences as one of the necessary conditions for evolution by natural selection to occur. Despite this foundational position of fitness, there (...) remains much debate over the nature of fitness, especially whether fitness differences can truly be said to cause evolutionary change. In recent years these debates have crystalized into two camps: (1) causalists, who see fitness differences as being one of the causes of evolutionary change, and (2) statisticalists, who deny the causal efficacy of fitness and instead hold that “fitness is a mere statistical, noncausal property of trait types” (Walsh 2010, 148). (shrink)
It is striking that the concept of fitness although fundamental in evolutionary theory, still remains ambiguous. I argue here that time, although usually neglected, is an important parameter in regards to the concept of fitness. I will show some of the benefits of taking it seriously using the example of recent debates over evolutionary transitions in individuality. I start from Okasha's assertion that once an evolutionary transition in individuality is completed an ontologically new level of selection emerges from (...) lower levels of organization. I argue that Okasha's claim to have identified two ontologically distinct levels of selection is an artifact created by an undeserved comparison between the fitness of the collective level and the fitness of its constituents. Once fitness is assessed over the same period of time at the two levels of organization it becomes clear that only one, unique process of selection is acting upon both levels. (shrink)
A major debate in the philosophy of biology centers on the question of how we should understand the causal structure of natural selection. This debate is polarized into the causal and statistical positions. The main arguments from the statistical side are that a causal construal of the theory of natural selection's central concept, fitness, either (i) leads to inaccurate predictions about population dynamics, or (ii) leads to an incoherent set of causal commitments. In this essay, I argue that neither (...) the predictive inaccuracy nor the incoherency arguments successfully undermine the causal account of fitness. (shrink)
We suggest that morbid jealousy falls on the extreme end of a jealousy continuum. Thus, many features associated with normal jealousy will be present in individuals diagnosed with morbid jealousy. We apply Boyer & Lienard's (B&L's) prediction one (P1; target article, sect. 7.1) to morbid jealousy, suggesting that fitness-related life-cycle dimensions predict sensitivity to cues, and frequency, intensity, and content of intrusive thoughts of partner infidelity. (Published Online February 8 2007).
Strong recent selection for social cognition may well explain the persistence of genes that predispose to schizophrenia. The specific mechanism responsible may be a skewed fitness function in which selection pushes the mean for advantageous mental traits perilously close to a “fitness cliff” where the system fails catastrophically in some individuals.
The upshot of the No Free Lunch theorems is that averaged over all fitness functions, evolutionary computation does no better than blind search (see Dembski 2002, ch 4 as well as Dembski 2005 for an overview). But this raises a question: How does evolutionary computation obtain its power since, clearly, it is capable of doing better than blind search? One approach is to limit the fitness functions (see Igel and Toussaint 2001). Another, illustrated in David Fogel’s work on (...) automated checker and chess playing (see, for instance, Chellapilla and Fogel 1999 and Fogel et al. 2004) and, more recently, given a theoretical underpinning by David Wolpert and William Macready (2005), is to limit optimization problems to search spaces consisting of agents that play competitively against one another. In this brief note, I focus on the latter attempt to get around the force of No Free Lunch. (shrink)
Grouping severe mental disorders into a global category is likely to lead to a “theory of everything” which forcefully explains everything and nothing. Speculation even at the phenotypic level of the single disorder cannot be fruitful, unless specific and testable models are proposed. Inclusive fitness must be incorporated in such models. (Published Online November 9 2006).
Using a classical life history model (the Smith & Fretwell model of the evolution of offspring size), it is demonstrated that even in the presence of overwhelming empirical support, the testability of predictions derived from evolutionary models can give no guarantee that the underlying fitness concept is sound. Non-awareness of this problem may cause considerable justified but avoidable criticism. To help understanding the variable use of fitness in evolutionary models and recognizing potentially problematic areas which need careful consideration, (...) a hierarchical classification of definitions of fitness used in evolutionary models is presented. As a conclusion, it is advocated to use the term fitness more conscientiously than currently often practised and to think more about ways to develop fitness-free evolutionary theories compatible with Darwin's ideas. (shrink)
This paper considers a variety of attempts to define fitness in such a way as to defend the theory of evolution by natural selection from the criticism that it is a circular argument. Each of the definitions is shown to be inconsistent with the others. The paper argues that the environment in which an animal evolves can be defined only with respect to the properties of the phenotype of the animal and that it is therefore not illuminating to try (...) to explain the phenotypic properties of the animal in terms of adaptation to an environment that is defined by those very properties. Furthermore, since there is no way that the environment can be defined independently of the presence of the animal there is no way that the quality of an animal can be assessed; and there can be no objective criteria by whichany form of selection can be carried out, therefore there can be no criteria by whichnatural selection can be carried out. It is proposed that fitness is nothing more than the production of offspring, that this is a phenotypic property like all the others, and if it is heritable then the offspring of the parents that produce the most offspring will themselves produce the most offspring, and that in principle it is impossible to account for this in terms of the other phenotypic properties of the fittest animals except by circular argument. Differential rates of reproduction are the causes of evolution and the phenotypic causes are strictly inexplicable. (shrink)
We offer a systematic examination of propensity interpretations of fitness, which emphasizes the role that fitness plays in evolutionary theory and takes seriously the probabilistic character of evolutionary change. We distinguish questions of the probabilistic character of fitness from the particular interpretations of probability which could be incorporated. The roles of selection and drift in evolutionary models support the view that fitness must be understood within a probabilistic framework, and the specific character of organism/environment interactions supports (...) the conclusion that fitness must be understood as a propensity rather than as a limiting frequency. (shrink)
Even outside of games, a wide range of otherwise puzzling common intuitions about fairness can be understood if the fundamental "game" of life is seen as wooing, i.e., attracting mates by showing that you have fit genes. The fairest social institutions are then those in which success correlates as much as possible with genetic fitness.
Fitness in the sense of actual rate of increase of genotypes, commonly used in population genetics, is contrasted with fitness in the ordinary sense (and Darwin's) of adaptedness of organisms. Fitness as actual reproductive success is interpreted as a function of variables representing intrinsic adaptive capacities and environmental properties. Adaptive capacities causally contribute to fitness as actual reproductive success which in turn, as relative increase of genotypes, determines evolutionary change. The propensity interpretation of fitness is (...) shown not to play a role in evolutionary explanation. (shrink)
Fluctuating asymmetry is more a signal of genetic fitness than a marker observable only to the researcher. Hence, it has to be demonstrated that low FA is an honest signal of genetic quality; this has not been demonstrated in Gangestad & Simpson's otherwise useful review.
The paper provides a new critical perspective on the propensity interpretation of fitness, by investigating its relationship to the propensity interpretation of probability. Two main conclusions are drawn. First, the claim that fitness is a propensity cannot be understood properly: fitness is not a propensity in the sense prescribed by the propensity interpretation of probability. Second, this interpretation of probability is inessential for explanations proposed by the propensity interpretation of fitness in evolutionary biology. Consequently, interpreting the (...) probabilistic dimension of fitness in terms of propensities is neither a strong motivation in favor of this interpretation, nor a possible target for substantial criticism. (shrink)
Given that knowledge consists of finite models of an infinitely complex reality, how can we explain that it is still most of the time reliable? Survival in a variable environment requires an internal model whose complexity (variety) matches the complexity of the environment that is to be controlled. The reduction of the infinite complexity of the sensed environment to a finite map requires a strong mechanism of categorization. A measure of cognitive complexity (C) is defined, which quantifies the average amount (...) of trial-and-error needed to find the adequate category. C can be minimized by "probability ordering" of the possible categories, where the most probable alternatives ("defaults") are explored first. The reduction of complexity by such ordering requires a low statistical entropy for the cognized environment. This entropy is automatically kept down by the natural selection of "fit" configurations. The high probability, "default" cognitive categorizations are then merely mappings of environmentally "fit" configurations. (shrink)
Although the Neo-Darwin Theory of Evolution is one of the most celebrated theories in science, nonetheless it has received many criticisms. These criticisms are documented and a new transdisciplinary theory of origin is introduced. Darwin's original argument was that natural selection, through heritable changes, changed simple organisms over time. These heritable changes are responsible for the complex plethora of life seen around us today. Darwin's original theory, however, was deconstructed after the (...) fact into a mutation-based theory. This mutation-based theory in its current form is an insufficient and indeed unnecessary transdisciplinary explanation. A subsequent statistical comparison between the six extant scientifically based primary theories of origin was undertaken and based on current biological knowledge a statistically significantly ( p < .05) best fit phenotypic model emerged. (shrink)
Although consensus appears to be on the horizon, the foundations of the theory of natural selection remain a matter of controversy. This paper looks at two recent challenges to the emerging "received view" of this theory. It argues that different views of the nature of scientific explanation are playing a pivotal role in the debates. Do explanations in biology fit the covering-law paradigm? What are the explanatory laws of biology like? Until agreement is reached on these fundamental questions, there is (...) little prospect for consensus on the foundations of the theory of natural selection. Furthermore, the three alternative positions identified in this paper each face serious challenges. (shrink)
Few problems in the philosophy of evolutionary biology are more widely disseminated and discussed than the charge of Darwinian evolution being a tautology. The history is long and complex, and the issues are many, and despite the problem routinely being dismissed as an introductory-level issue, based on misunderstandings of evolution, it seems that few agree on what exactly these misunderstandings consist of. In this paper, I will try to comprehensively review the history and the issues. Then, I will try to (...) present the following “solution”, or, one might say, “dissolution”, of the problem, and consider the wider implications of formal, or schematic, explanations in science: yes, the principle of natural selection is a tautology, and so what? It is a promissory note for actual, physical, explanations in particular cases, and is none the worse for that. This is not a new argument, of course, but it does point up the importance of formal schematic models in science. (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 (e.g. clonal species, colonial species, multi-species communities) 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 (or persistence) over that of reproduction. (shrink)
In this paper I discuss recent debates concerning etiological theories of functions. I defend an etiological theory against two criticisms, namely the ability to account for malfunction, and the problem of structural doubles. I then consider the arguments provided by Bigelow and Pargetter (1987) for a more forward looking account of functions as propensities or dispositions. I argue that their approach fails to address the explanatory problematic for which etiological theories were developed.
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)
At one level, this paper is a lament and a warning. I lament biologists borrowing well-known terms and then drastically and awkwardly changing their meanings, and I warn about the mischief this does. Biology''s public image is at stake, as is its general usefulness. At another level, I attempt to clarify the misnamed concepts, beyond what has been achieved in recent philosophical writings. This helps to account for the mischief, and to see how it might be avoidable. But the most (...) important thing about the paper is that, at a third level, it is an argument against physicalism and materialism, especially those variants which deny the autonomy of organisms and the existence of intrinsic goods. Interpreting biology from the point of view of those denials leads to unsatisfactory and even bizarre results. (shrink)
Schizophrenia may not have reduced reproductive success in ancestral times as much as it does today, so explaining how genes for it evolved is more understandable given this prehistoric perspective. Ethological analysis of schizophrenia – understanding how basic emotional behaviors, such as dominance striving, are affected by the condition – might prove useful for comprehending and treating its social emotional symptoms.
The expansion of human evolutionary theory into the domain of personal and environmental determinants of mating strategies is applauded. Questions are raised about the relation between fluctuating asymmetry (FA), testosterone, and body size and their effects on male behavior and outcomes. Low FA males' short-term mating pattern is considered in the context of an evolved tendency for closer and longer human relationships.
