Constraining the adaptationism debate

This contribution to the adaptationism debate elaborates the nature of constraints and their importance in evolutionary explanation and argues that the adaptationism debate should be limited to the issue of how to privilege causes in evolutionary explanation. I argue that adaptationist explanations are deeply conceptually dependent on developmental constraints, and explanations that appeal to constraints are dependant on the results of natural selection. I suggest these explanations should be integrated into the framework of historical causal explanation. Each strategy explicitly appeals to some aspect of the evolutionary process, while implicitly appealing to others. Thus, adaptationists and anti-adaptationists can offer complementary causal explanations of the same explanandum. This eliminates much of the adaptationism debate and explains why its adversaries regularly agree with each other more than they would like. The adaptationism issue that remains is a species of the general issue of how to privilege causes in explanation. I show how a proposed solution to this general problem might be brought to bear on evolutionary explanations, and investigate some difficulties that might arise due to the nature of the evolutionary process.     

Causal and Mechanistic Explanations in Ecology

How are scientific explanations possible in ecology, given that there do not appear to be many-if any-ecological laws? To answer this question, I present and defend an account of scientific causal explanation in which ecological generalizations are explanatory if they are invariant rather than lawlike. An invariant generalization continues to hold or be valid under a special change-called an intervention-that changes the value of its variables. According to this account, causes are difference-makers that can be intervened upon to manipulate or control their effects. I apply the account to ecological generalizations to show that invariance under interventions as a criterion of explanatory relevance provides interesting interpretations for the explanatory status of many ecological generalizations. Thus, I argue that there could be causal explanations in ecology by generalizations that are not, in a strict sense, laws. I also address the issue of mechanistic explanations in ecology by arguing that invariance and modularity constitute such explanations.     

Conjecture and explanation: A reply to Reydon

Reydon (2012) comments on my account of how-possibly explanation (Forber, 2010). I distinguish between three types of explanation (global how-possibly, local how-possibly, and how actually) and argue that these distinctions track various roles explanations play in evolutionary biology. While Reydon accepts the distinctions, he questions whether the two different types of how-possibly explanation count as genuine explanations. He summarizes his analysis with a slogan: “global how-possibly explanations are explanations but not how-possibly; local explanations are how-possibly but not explanations.” Reydon’s commentary raises a number of insightful points, and I will not be able to address them all. Instead, after clarifying certain points in my original paper (4 1), I will respond to Reydon’s slogan by addressing whether global how-possibly explanations should count as explaining how possible (4 2), and what (so-called) local how-possibly explanations are, if not explanations (4 3).     

Adaptation and novelty: teleological explanations in evolutionary biology

Knives, birds' wings, and mountain slopes are used for certain purposes: cutting, flying, and climbing. A bird's wings have in common with knives that they have been 'designed' for the purpose they serve, which purpose accounts for their existence, whereas mountain slopes have come about by geological processes independently of their uses for climbing. A bird's wings differ from a knife in that they have not been designed or produced by any conscious agent; rather, the wings, like the slopes, are outcomes of natural processes without any intentional causation. Evolutionary biologists use teleological language and teleological explanations. I propose that this use is appropriate, because teleological explanations are hypotheses that can be subject to empirical testing. The distinctiveness of teleological hypotheses is that they account for the existence of a feature in terms of the function it serves; for example, wings have evolved and persist because flying is beneficial to birds by increasing their chances of surviving and reproducing. Features of organisms that are explained with teleological hypotheses include structures, such as wings; processes, such as development from egg to adult; and behaviours, such as nest building. A proximate explanation of these features is the function they serve; an ultimate explanation that they all share is their contribution to the reproductive fitness of the organisms. I distinguish several kinds of teleological explanations, such as natural and artificial, as well as bounded and unbounded, some of which but not others apply to biological explanations.     

How-possibly explanations as genuine explanations and helpful heuristics: A comment on Forber

Recently, Forber introduced a distinction between two kinds of how-possibly explanation, global and local how-possibly explanation, and argued that both play genuinely explanatory roles in evolutionary biology. In this paper I examine the nature of these two kinds of how-possibly explanations, focusing on the question whether they indeed constitute genuine explanations. I will conclude that one of Forber's kinds of how-possibly explanation may be thought of as a kind of genuine explanation but not as a kind of how-possibly explanation, while the other kind plays a heuristic role and should not be conceived of as a kind of explanation at all.     

Constructing a query-able radial basis function artificial neural network

Artificial neural networks will be more widely accepted as standard engineering tools if their reasoning process can be made less opaque. This paper describes NetQuery, an explanation mechanism that extracts meaningful explanations from trained Radial Basis Function (RBF) networks. RBF networks are well suited for explanation generation because they contain a set of locally tuned units. Standard RBF networks are modified to identify dependencies between the inputs, to be sparsely connected, and to have an easily interpretable output layer. Given these modifications, the network architecture can be used to extract "Why?" and "Why not?" explanations from the network in terms of excitatory and inhibitory in-puts and their linear relationships, greatly simplified by a run-time pruning algorithm. These query results are validated by creating an expert system based on the explanations. NetQuery is also able to inform a user about a possible change in category for a given pattern by responding to a "How can I...?" query. This kind of query is extremely useful when analyzing the quality of a pattern set.     

Hempel's view on functional explanation some critical comments

Summary Functional explanations are regarded as a special type of explanation by many biologists. Philosophers of science tend to agree that they are weak forms of the common modes of explanation, although the elucidation of the logical structure involved is difficult. The present paper shows that Hempel's reconstruction of functional explanations is inadequate on pragmatic grounds. Thus his conclusion that such explanations are necessarily weak is also objectionable. There is no reason for allotting functional explanations a special logical status.     

Darwin was a teleologist

It is often claimed that one of Darwin's chief accomplishments was to provide biology with a non-teleological explanation of adaptation. A number of Darwin's closest associates, however, and Darwin himself, did not see it that way. In order to assess whether Darwin's version of evolutionary theory does or does not employ teleological explanation, two of his botanical studies are examined. The result of this examination is that Darwin sees selection explanations of adaptations as teleological explanations. The confusion in the nineteenth century about Darwin's attitude to teleology is argued to be a result of Darwin's teleological explanations not conforming to either of the dominant philosophical justifications of teleology at that time. Darwin's explanatory practices conform well, however, to recent defenses of the teleological character of selection explanations.I would like to thank John Beatty, David Hull and one of this journal's readers for constructive comments on an earlier draft of this paper.     

The failure of global migration governance

The deconstruction of the moral polity around forced migration proposed by Thomas Faist in his article “The moral polity of forced migration” can, in some ways, be interpreted as an analysis of the failure of global migration governance. In this comment, I review the challenges faced by those claiming their human rights, suggesting – in addition to Faist’s explanations – some further causes of and consequences for the current situation. I then explore the type of claim made by refugees in their protests, using the concept of weak agency, which relativizes the statement made by Faist that their claim is not subversive.     

Inferential explanations in biology

Among philosophers of science, there is now a widespread agreement that the DN model of explanation is poorly equipped to account for explanations in biology. Rather than identifying laws, so the consensus goes, researchers explain biological capacities by constructing a model of the underlying mechanism.We think that the dichotomy between DN explanations and mechanistic explanations is misleading. In this article, we argue that there are cases in which biological capacities are explained without constructing a model of the underlying mechanism. Although these explanations do not conform to Hempel’s DN model (they do not deduce the explanandum from laws of nature), they do invoke more or less stable generalisations. Because they invoke generalisations and have the form of an argument, we call them inferential explanations. We support this claim by considering two examples of explanations of biological capacities: pigeon navigation and photoperiodism. Next, we will argue that these non-mechanistic explanations are crucial to biology in three ways: (i) sometimes, they are the only thing we have (there is no alternative available), (ii) they are heuristically useful, and (iii) they provide genuine understanding and so are interesting in their own right.In the last sections we discuss the relation between types of explanations and types of experiments and situate our views within some relevant debates on explanatory power and explanatory virtues.     

Mechanisms,resources, and background conditions

Distinguishing mechanistic components from mere causally relevant background conditions remains a difficulty for mechanistic accounts of explanation. By distinguishing resources from mechanical parts, I argue that we can more effectively draw this boundary. Further, the distinction makes obvious that there are distinctive resource explanations which are not captured by a traditional part-based mechanistic account. While this suggests a straightforward extension of the mechanistic model, I argue that incorporating resources and resource explanations requires moving beyond the purely local account of levels that some mechanists advocate.     

Engaging students in constructing scientific explanations in biology classrooms: a lesson-design model

Abstract

Constructing scientific explanations of natural phenomena is an important aim of science education. Explanation oriented science teaching approaches encourage learners to engage in sense-making discussions and construct the causal accounts of the phenomena under study. This article demonstrates a lesson-design model that guides biology teachers on how to integrate explanation oriented teaching in their everyday practice. The proposed model includes six phases: (1) presenting a hooking activity; (2) formulating a how-why type focus question; (3) constructing the initial causal story; (4) using authentic data, scientific facts, principles, and disciplinary core ideas to revise-refine the causal story; (5) discussing-rewriting the refined causal story; (6) applying the causal-mechanistic knowledge in a new context or problem scenario. An eleventh-grade lesson on the topic ‘protein biosynthesis in cells’ serves an example about how this model can be operationalized to design and implement explanation oriented biology lessons.     

Two explanations of the dawn chorus compared: how monotonically changing light levels favour a short break from singing

I used optimality modelling to compare two of the most plausible and general explanations for the dawn and dusk peaks in bird song output. Kacelnik's explanation is that foraging is inefficient in poor light, but that social interactions are less affected, making singing more worthwhile than foraging. McNamara et al.'s explanation is based on stochasticity in foraging success and overnight energy requirements; it has been extensively analysed with stochastic dynamic programming models. Both explanations are now incorporated into this sort of model. I used various functions to link success of foraging and singing to time of day, but assumed that above some light level there is no further effect. Kacelnik's explanation has as strong an effect as stochasticity in generating dawn and dusk choruses. It also predicts short pauses in the singing output just after the dawn chorus and before the dusk chorus. The former arises because birds delay foraging when it will become more profitable later, until foraging success reaches a plateau, when the energetic debt accumulated makes them forage. The principle of this see-saw double switch in behaviours may apply to other explanations for the dawn chorus, and to other shifts in behaviour when conditions change gradually. The model predicts that from day to day cloud cover determines when a dawn chorus starts, but that overnight temperature and wind strength have more effect on chorus intensity and duration. I discuss what sort of observational and experimental data on singing routines would better test this model. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Mechanical explanation of nature and its limits in Kant's Critique of judgment

In this paper I discuss two questions. What does Kant understand by mechanical explanation in the Critique of judgment? And why does he think that mechanical explanation is the only type of the explanation of nature available to us? According to the interpretation proposed, mechanical explanations in the Critique of judgment refer to a particular species of empirical causal laws. Mechanical laws aim to explain nature by reference to the causal interaction between the forces of the parts of matter and the way in which they form into complex material wholes. Just like any other empirical causal law, however, mechanical laws can never be known with full certainty. The conception according to which we can explain all of nature by means of mechanical laws, it turns out, is based on what Kant calls 'regulative' or 'reflective' considerations about nature. Nothing in Kant's Critique of judgment suggests that these considerations can ever be justified by reference to how the natural world really is. I suggest that what, upon first consideration, appears to be a thoroughly mechanistic conception of nature in Kant is much more limited than one might have expected.     

Ultimate explanations concern the adaptive rationale for organism design

My understanding is that proximate explanations concern adaptive mechanism and that ultimate explanations concern adaptive rationale. Viewed in this light, the two kinds of explanation are quite distinct, but they interact in a complementary way to give a full understanding of biological adaptations. In contrast, Laland et al. (2013)—following a literal reading of Mayr (Science 134:1501–1506, 1961)—have characterized ultimate explanations as concerning any and all mechanisms that have operated over the course of an organism’s evolutionary history. This has unfortunate consequences, such as allowing random drift to form the basis for ultimate explanations, and allowing proximate and ultimate explanations to bleed into each other until their distinction is meaningless. Here, I suggest Laland et al’s explanatory framework of “reciprocal causation” is not conducive to successful biological science, and that they have misunderstood key elements of the theory of Darwinian adaptation.     

Developmental instability and within-population variation in sex expression by andromonoecious Euphorbia xanti

Within an area spanning approximately 1 km², individuals belonging to a population of andromonoecious Euphorbia xanti range in their sex expression from all-staminate to all-cosexual. In this study I attempt to evaluate this variation using measures of non-directional asymmetry as potential indicators of developmental instability. Assuming that developmental homeostasis and sex allocation are sensitive to the same, or correlated, stress factors, I expected an adaptive explanation to be manifested in a monotonic relationship between asymmetry and 'femaleness' (i.e. the per-plant proportion of cosexual cyathia). Unexpectedly, per-plant mean asymmetry peaked at intermediate sexuality (femaleness of approx. 0.5). At the same time, intermediate sexuality was qualitatively associated with relatively low probabilities of cosexual cyathia developing fruit. I discuss two hypothetical explanations for these observations.     

Personhood diagnostics: personal attributes and clinical explanations of pain

This article examines an explanation circulating within a U.S. multidisciplinary pediatric pain clinic that links the neurobiology of functional pain disorders to desirable personal attributes such as smartness and creativity. Drawing on ethnographic observations and the analysis of video-recorded clinical interactions and focusing on two cases, I introduce the term personhood diagnostics to explore how the explanatory framework worked not only to pinpoint a pathophysiological mechanism for pain to legitimize it as "real" but also to cast patients as virtuous persons. In doing so, it laid the groundwork for an ethic of clinical care that privileged the patient's responsibility for treatment. Within this narrative logic, diagnostic explanations reveal not only causal pathways but also predictive claims about recovery. By considering what is at stake when personal attributes are marshaled within a neurobiological diagnostic register that also lays out the patient's role in healing, this article complicates psychosomatic accounts of pain.     

Nature of Deleterious Mutation Load in Drosophila

Much population genetics and evolution theory depends on knowledge of genomic mutation rates and distributions of mutation effects for fitness, but most information comes from a few mutation accumulation experiments in Drosophila in which replicated chromosomes are sheltered from natural selection by a balancer chromosome. I show here that data from these experiments imply the existence of a large class of minor viability mutations with approximately equivalent effects. However, analysis of the distribution of viabilities of chromosomes exposed to EMS mutagenesis reveals a qualitatively different distribution of effects lacking such a minor effects class. A possible explanation for this difference is that transposable element insertions, a common class of spontaneous mutation event in Drosophila, frequently generate minor viability effects. This explanation would imply that current estimates of deleterious mutation rates are not generally applicable in evolutionary models, as transposition rates vary widely. Alternatively, much of the apparent decline in viability under spontaneous mutation accumulation could have been nonmutational, perhaps due to selective improvement of balancer chromosomes. This explanation accords well with the data and implies a spontaneous mutation rate for viability two orders of magnitude lower than previously assumed, with most mutation load attributable to major effects.     

A behavioral analysis of altruism

Altruistic acts have been defined, in economic terms, as “…costly acts that confer economic benefits on other individuals” (Fehr and Fischbacher, 2003). In multi-player, one-shot prisoner's dilemma games, a significant number of players behave altruistically; their behavior benefits each of the other players but is costly to them. We consider three potential explanations for such altruism. The first explanation, following a suggestion by the philosopher Derek Parfit, assumes that players devise a strategy to avoid being free-loaders—and that in the present case this strategy dictates cooperation. The second explanation says that cooperators reject the one-shot aspect of the game and behave so as to maximize reward over a series of choices extending beyond the present situation (even though reward is not maximized in the present case). This explanation assumes that people may learn to extend the boundaries of their selves socially (beyond their own skin) as well as temporally (beyond the present moment). We propose a learning mechanism for such behavior analogous to the biological, evolutionary mechanism of group selection. The third explanation assumes that people's altruism is based on a straightforward balancing of undiscounted costs to themselves against discounted benefits to others (social discounting). The three proposed explanations of altruism complement each other.