In the Preface to his recent philosophy of biology (1988) and in his earlierGrowth of Biological Thought(1982), Ernst Mayr emphasized that recent progress in evolutionary biology is a result of conceptual clarification, not a consequence of improved measurements or better scientific laws. Although complete agreement on the meaning of key concepts is not essential for all communication in science (see Hull 1988, pp. 6-7,513), we likewise believe that conceptual clarification is perhaps the most important key to progress in community ecology. (...) In order to investigate some of the reasons that might explain why community ecology has been unable to arrive at a widely accepted general theory, in this essay we analyze “stability,” one of its most important foundational concepts. After reviewing the stability concept and sketching its associated problems, we assess the epistemological status of four difficulties with the concept. (shrink)

What are biological species? Aristotelians and Lockeans agree that they are natural kinds; but, evolutionary theory shows that neither traditional philosophical approach is truly adequate. Recently, Michael Ghiselin and David Hull have argued that species are individuals. This claim is shown to be against the spirit of much modern biology. It is concluded that species are natural kinds of a sort, and that any 'objectivity' they possess comes from their being at the focus of a consilience of inductions.

In lieu of an abstract, here is a brief excerpt of the content:Reviewed by:Ecological Ethics: An IntroductionDavid Keller (bio)Patrick Curry, Ecological Ethics: An Introduction. Malden, Massachusetts: Polity Press, 2007, 173pages.Were I in Bath having drinks with Patrick Curry, we would have much to agree about. Explaining his choice of title of his book, Ecological Ethics, he rightly points out that the more common descriptor "environmental ethics" presupposes a dualism between human beings and the nonhuman environment—an assumption which is itself anthropocentric (...) (p. 4). For philosophers interested in studying the human/ nonhuman dynamic, the legitimacy of anthropocentrism is itself an open question. Because the word 'ecology' treats humans, as biota, as integral parts of ecological systems, the phrase "ecological ethics" is less presumptuous and hence more accurate. The word 'ecological' also has the benefit of conveying the message that the subject is notgoing to involve extending moral considerability from humans out into the "environment." Instead, ecological systems as the locus of value provide the starting point for the elaboration of ethics (p. 2). For Curry, as for Leopold (1960) and Callicott (1989), "ecological community" is coextensive with the ethical community.To correlate the ethical community with the biotic community within the rubric of "ecological ethics" is nothing novel. Curry's claim that "there is something ancient about an ecological ethic" (p. 7) got me thinking: [End Page 153]prior to Abrahamic monotheism and Greek rationalism, ancient peoples, particularly nomadic hunter-gatherers, probably considered themselves as integral parts of what encompassed them, moving with herds, in concert with meteorological and seasonal changes, seeing themselves as one amongst other living beings. They probably did not see themselves apart from the "environment" as we have learned to do. Then with the advent of agriculture, linear furrows and controlled inundations must have fostered an addictive sense of security from flood and famine. Later, the innovations of industrial civilization further distanced us from the caprice of nature's wild vicissitudes. Yet that comfort comes at the expense of lost awareness of our responsibilities as bioticcitizens. Therefore, Curry says, following Sylvan (1973), we need a new ecological ethic since traditional Western morality "is no longer up to the job" (ibid.).Curry remarks that ethics, cast in this light, is not something "optional," something to be addressed after one's belly is full, debts settled, and lodging secured. Rather, ethics cuts directly to the core of human action, of all human activity (p. 5)—a claim reminiscent of Socrates' exhortation to Thrasymachus that it is no small matter that they are discussing, nothing of less importance than the right way to live one's life (Plato 2005, p. 603).Over the first sips of ale, I would praise him for giving his book a simple and straightforward structure that makes a challenging subject accessible, especially to students. After laying down the groundwork of basic concepts in moral philosophy (chapter 3)—objectivism versus relativism, the problem of the is/ought gap, religious morality and environmental philosophy (domination, stewardship, and managerialism), and virtue and rule-based ethics (chapter 4)—Curry addresses axiology (chapter 5). Are humans the sole locus of value (anthropocentrism), or are there other entities worthy of some sort of moral consideration who themselves do not carry the burden of moral responsibility (zoocentrism, biocentrism, ecocentrism)? Curry answers the latter in the affirmative, arguing that ontological interconnectedness of humans with other living beings within ecological systems discloses that something greater than humanity is the locus of value (p. 46).The most useful part of the book for my students out in Utah would be the middle chapters (6–8) in which Curry casts degrees of nonanthropocentrism [End Page 154]in shades of green. These shades range from light green or "shallow" anthropocentric ethics such Bookchin's Social Ecology (p. 50), Hardin's Lifeboat Ethics (pp. 52–54), and mainstream environmentalism (p. 51), through medium green ethics based on the extension of traditional human-oriented moral philosophy to nonhumans such as Singer's Animal Liberation (pp. 56–59), Regan's Animal Rights (pp. 59–60), and Taylor's Biocentrism (pp. 60–62). Curry proceeds to the dark green ethics of ecocentrism, such as Land Ethics (pp. 65–68), the Gaia Hypothesis (pp. 68–71... (shrink)

Third World countries are not pursuing scientific and technological policies leading to the development of strong biotechnological industries. Their leaders have been misled into believing that modern biotechnological industries can be built in the absence of strong, intellectually aggressive, and original scientific schools. Hence, they do not strive to reform their universities, which have weak commitments to research, and do not see the importance of having research hospitals able to generate excellent and relevant clinical investigation. These strategic gaps in scientific (...) capability, the lack of governmental and corporate research funding, and the dependent nature of the chemical and pharmaceutical industries of the Third World make the development of competitive biotechnology a highly improbable event. If the present trend continues, underdeveloped countries will continue to be testing grounds for biological materials and agents, sources of valuable germplasm, and markets for high-value-added products and processes invented and manufactured in the First World. This article recommends that the international organizations collaborate in the urgent task of educating the Third World political leaders and administrators in the real problems connected with the generation of high technology. (shrink)

A central thesis of intelligent‐design theorists is that physical and chemical laws and chance are insufficient to account for irreducibly complex biological structures and that intelligent design is necessary to account for such phenomena. This assertion, however, still implies a reductionist ontology. We need to recognize that reality displays multiple modes of being beyond simply chemical and physical modes of being, each of which is governed by laws for that mode of being. This essay argues for an alternate framework for (...) understanding life phenomena that is neither philosophical materialism nor intelligent‐design theory. (shrink)

This paper develops an account of explanation in biology which does not involve appeal to laws of nature, at least as traditionally conceived. Explanatory generalizations in biology must satisfy a requirement that I call invariance, but need not satisfy most of the other standard criteria for lawfulness. Once this point is recognized, there is little motivation for regarding such generalizations as laws of nature. Some of the differences between invariance and the related notions of stability and resiliency, due respectively to (...) Sandra Mitchell and Brian Skyrms, are explored. (shrink)

David Hull's (1988c) model of science as a selection process suffers from a two-fold inability: (a) to ascertain when a lineage of theories has been established; i.e., when theories are descendants of older theories or are novelties, and what counts as a distinct lineage; and (b) to specify what the scientific analogue is of genotype and phenotype. This paper seeks to clarify these issues and to propose an abstract model of theories analogous to particulate genetic structure, in order to reconstruct (...) relationships of descent and identity. (shrink)

Memes are an idea whose time has come, again, and again, and again, but which has never really made it beyond metaphor. Anthropologist Robert Aunger’s book 'The Electric Meme' is a new attempt to take it to the next stage, setting up a research program with proper models and theoretical entities. He succeeds partially, with some contributions to the logic of replication, but in the end, his proposal for the substrate of memes is a non-solution to a central problem of (...) memetics. (shrink)

Erwin Schrödinger’s 1944 publication What is Life? is a classic of twentieth century science writing. In his book, Schrödinger discussed the chromosome fibre as the seat of heredity and variation thanks to a hypothetical aperiodic structure – a suggestion that famously spurred on a generation of scientists in their pursuit of the gene as a physico-chemical entity. While historical attention has been given to physicists who were inspired by the book, little has been written about its biologist readers. This paper (...) examines the case of the English evolutionary botanist and cytologist Irène Manton, who took an interest in What is Life? for its relevance to her own research in chromosome structure as a clue to plant phylogeny. Drawing on recently discovered correspondence between Manton and Schrödinger, the paper reconstructs Manton ‘s path to the book and her response to it by way of throwing new light on a pivotal moment in the history of the debate on chromosome structure. (shrink)

In this article, I examine Luhmann’s, Bunge’s and others’ views on emergence, and argue that Luhmann’s epistemological construal of emergence in terms of Totalausschluss (total exclusion) is both ontologically flawed and detrimental to an appropriate understanding of the distinctive features of social emergence. By contrast, Bunge’s rational emergentism, his CESM model, and Wimsatt’s characterization of emergence as nonaggregativity provide a useful framework to investigate emergence. While researchers in the field of social theory and sociology tend to regard Luhmann as the (...) sole representative of systems theory, the latter has been characterized by its diversity, and the writings of such systems theorists as Mario Bunge deserve more (critical) attention from social researchers than they receive at present. Finally, this article suggests that the perennial debate over methodological individualism and holism in social science may make real progress if such ambiguous terms as reduction and reductionism are elucidated before they are employed. (shrink)

In this article, I examine Luhmann’s, Bunge’s and others’ views on emergence, and argue that Luhmann’s epistemological construal of emergence in terms of Totalausschluss (total exclusion) is both ontologically flawed and detrimental to an appropriate understanding of the distinctive features of social emergence. By contrast, Bunge’s rational emergentism, his CESM model, and Wimsatt’s characterization of emergence as nonaggregativity provide a useful framework to investigate emergence. While researchers in the field of social theory and sociology tend to regard Luhmann as the (...) sole representative of systems theory, the latter has been characterized by its diversity, and the writings of such systems theorists as Mario Bunge deserve more (critical) attention from social researchers than they receive at present. Finally, this article suggests that the perennial debate over methodological individualism and holism in social science may make real progress if such ambiguous terms as reduction and reductionism are elucidated before they are employed. (shrink)

This article illuminates why Nicolás Palacios’s 1904 monograph, Raza chilena:Libro escrito por un Chileno i para los Chilenos [Chilean Race: A Book Written by a Chilean for Chileans], is central to the creation of a myth of Chilean racial homogeneity at the turn of the twentieth century. Placing Palacios in the context of Latin American eugenic discourse, it demonstrates how he selected a specific racial origin story in order to accommodate his belief in racial hierarchy while also depicting race mixing (...) in a positive light. Specifically, the article highlights how the myth of Chilean racial homogeneity elided the difference between the term “mestizo,” which was applied to people of mixed racial heritage, and “white.” I contend that Palacios sought to differentiate Chileans from other Latin Americans by emphasizing their racial distinctiveness. The article therefore highlights that Latin American eugenics was concerned with the creation of national narratives that historicized particular racial mixtures in order to reify and affirm national differences. As such, it connects to literature regarding the history of eugenics, race, nation, and the creation of whiteness. (shrink)

The invisible object, in the eighteenth century, is not an evidence. It is the result of textual and semantic learning. Which concrete strategies are used to construct and depict objects out of sight? How do we make them a cognitive reality acceptable to a scientific community? This paper first highlights the conditions for the emergence of a field of microscopic knowledge and its epistemological consequences. Then we consider the microscopic gaze in terms of learning, situated between the act of observation (...) as such and discursive practices. We conclude by studying a concrete case of “negotiation of the invisible” in a correspondence between Carl Linnaeus and John Ellis concerning corpuscles observed in mushroom infusions. (shrink)

This paper contributes to two debates: the debate about language evolution and the debate about the foundations of human collaboration. While both cooperation and language may give the impression of being adaptations that evolved for the “good of the group,” it is well established that the evolution of complex traits cannot be a direct result of group selection. In this paper I suggest how this tension can be solved: both language and cooperation evolved in a unique two-level evolutionary system which (...) was triggered by a well-documented geological event—the drying out of the climate—in East Africa, which subsequently reduced the intermating between groups and thus made it possible that the mechanism that produced differences between groups could be the target of natural selection on the group level. If a social form of selection produced differences in fitness between groups, the displacement process between groups would indirectly select those forms of social selection that produce groups that would displace all others. The main hypothesis presented in this paper is that, in this situation, a backchannel between the two levels of selection naturally evolves. A backchannel between the two levels would, for example, emerge when sexual selection was sensitive to the individual’s contribution to the group. Examples of systems utilizing a backchannel are nerve cells being better nourished when used more frequently, enabling them to be conducive to the survival of the whole organism, or a law firm in which all employees get paid to the extent that they contribute to the survival and success of the firm. In both cases, the selection on the higher level informs the selection on the lower level. The aim of the paper is to illuminate these rather opaque claims, to which the reader probably has many objections in this abridged form. (shrink)

Of all contemporary social theorists, Luhmann has best understood the centrality of the concept of meaning to social theory and has most extensively worked out the notion's implications. However, despite the power of his theory, the theory suffers from difficulties impeding its reception. This article attempts to remedy this situation with some critical arguments and proposals for revision. First, the theory Luhmann adopted from biology as the basis of his own theory was a poor choice since that theory has no (...) explanatory power, being purely descriptive; furthermore, that theory is fundamentally flawed since it implies that viruses are impossible. Second, Luhmann's theory of meaning cannot coherently make the social domain autonomous as he desires since Luhmann does not take into account the distinction between syntax and semantics. By introducing this distinction, making clear that social systems consist of rules, not just communications, and raising the rule concept to the same prominence in social theory as those of actor and system, autonomy can be maintained while avoiding the counterintuitive aspects of Luhmann's theory. (shrink)

The progress towards mathematization or, in a broader context, towards an increased “objectivity” is one of the main trends in the development of biological systematics in the past century. It is commonplace to start the history of numerical taxonomy with the works of R. R. Sokal and P. H. A. Sneath that in the 1960s laid the foundations of this school of taxonomy. In this article, I discuss the earliest research program in this field, developed in the 1920s by the (...) Russian entomologist and biometrician Eugen (Evgeniy Sergeevich) Smirnov. The theoretical and methodological grounds of this program are considered based on the published works of Smirnov as well as some archival sources. The influence of Smirnov’s evolutionary (mechano-Lamarckian) convictions on the development of this project of “exact systematics” is analyzed as well as the author’s attempts to establish a novel concept of “mathematical essentialism” in animal taxonomy. The probable causes of the failure of Smirnov’s project are viewed from both externalist and internalist perspectives, including the opposition to the use of quantitative methods in biology by some of the Lysenkoist ideologists in the USSR. A brief comparison of Smirnov’s research program with that developed 40 years later by Sokal and Sneath is provided. (shrink)

Darwin provided us with a powerful theoretical framework to explain the evolution of living systems. Natural selection alone, however, has sometimes been seen as insufficient to explain the emergence of new levels of selection. The problem is one of “circularity” for evolutionary explanations: how to explain the origins of Darwinian properties without already invoking their presence at the level they emerge. That is, how does evolution by natural selection commence in the first place? Recent results in experimental evolution suggest a (...) way forward: Paul Rainey and his collaborators have shown that Darwinian properties could be exogenously imposed via what they call “ecological scaffolding.” This could solve the “black box” dilemma faced by Darwinian explanations of new levels of organization. Yet, despite “scaffolding” recently becoming a popular term in the study of cognition, culture, and evolution, the concept has suffered from vagueness and ambiguity. This article aims to show that scaffolding can be turned into a proper scientific concept able to do explanatory work within the context of the major evolutionary transitions. Doing so will allow us to once again extend the scope of the Darwinian model of evolution by natural selection. (shrink)

In 1869, Johann Friedrich Miescher discovered a new substance in the nucleus of living cells. The substance, which he called nuclein, is now known as DNA, yet both Miescher’s name and his theoretical ideas about nuclein are all but forgotten. This paper traces the trajectory of Miescher’s reception in the historiography of genetics. To his critics, Miescher was a “contaminator,” whose preparations were impure. Modern historians portrayed him as a “confuser,” whose misunderstandings delayed the development of molecular biology. Each of (...) these portrayals reflects the disciplinary context in which Miescher’s work was evaluated. Using archival sources to unearth Miescher’s unpublished speculations—including an analogy between the hereditary material and language, and a speculation that a series of asymmetric carbon atoms could account for hereditary variation—this paper clarifies the ways in which the past was judged through the lens of contemporary concerns. It also shows how organization, structure, function, and information were already being considered when nuclein was first discovered nearly 150 years ago. (shrink)

Many people who claim that evolution and theism are in tension assume that God, being omnipotent, could create life in different ways. For instance, Paul Draper has argued that the fact that life evolved on earth supports naturalism over theism. However, for there to be a probabilistic tension between naturalism and theism, because of the fact of evolution, a certain background assumption must be true, namely, that God could have made biological organisms and species through an act of Genesis-style special (...) creation, or some combination of evolution and special creation. But that background assumption is potentially faulty. Why? Because special creation presupposes that biological organisms and species are spatiotemporally unrestricted entities, and if the dominant paradigm in biology, and philosophy of biology, on the ontological status of organisms and species is correct, then they are spatiotemporally restricted entities. (shrink)

Industrial melanism, according to the traditional explanation, amounts to niche construction since it involves changes in predation pressure. Indeed, it would be difficult to imagine selection without niche construction. This cannot be what Laland, Odling-Smee & Feldman mean. They offer convincing examples, but they should provide a better definition of “niche construction” to indicate how their view supplements traditional evolutionary biology.

Instances of explanatory reduction are often advocated on metaphysical grounds; given that the only real things in the world are subatomic particles and their interaction, we have to try to explain everything in terms of the laws of physics. In this paper, we show that explanatory reduction cannot be defended on metaphysical grounds. Nevertheless, indispensability arguments for reductive explanations can be developed, taking into account actual scientific practice and the role of epistemic interests. Reductive explanations might be indispensable to address (...) some epistemic interest answering a specific explanation-seeking question in the most accurate, adequate and efficient way. Just like explanatory pluralists often advocate the indispensability of higher levels of explanation pointing at the pragmatic value of the explanatory information obtained on these higher levels, we argue that explanatory reduction—traditionally understood as the contender of pluralism—can be defended in a similar way. The pragmatic value reductionist, lower level explanations might have in the biomedical sciences and the social sciences is illustrated by some case studies. (shrink)

Ernst Mayr argued that the emergence of biology as a special science in the early nineteenth century was possible due to the demise of the mathematical model of science and its insistence on demonstrative knowledge. More recently, John Zammito has claimed that the rise of biology as a special science was due to a distinctive experimental, anti-metaphysical, anti-mathematical, and anti-rationalist strand of thought coming from outside of Germany. In this paper we argue that this narrative neglects the important role played (...) by the mathematical and axiomatic model of science in the emergence of biology as a special science. We show that several major actors involved in the emergence of biology as a science in Germany were working with an axiomatic conception of science that goes back at least to Aristotle and was popular in mid-eighteenth-century German academic circles due to its endorsement by Christian Wolff. More specifically, we show that at least two major contributors to the emergence of biology in Germany—Caspar Friedrich Wolff and Gottfried Reinhold Treviranus—sought to provide a conception of the new science of life that satisfies the criteria of a traditional axiomatic ideal of science. Both C.F. Wolff and Treviranus took over strong commitments to the axiomatic model of science from major philosophers of their time, Christian Wolff and Friedrich Wilhelm Joseph Schelling, respectively. The ideal of biology as an axiomatic science with specific biological fundamental concepts and principles thus played a role in the emergence of biology as a special science. (shrink)

For over a century it has been believed that Alfred Russel Wallace and Henry Walter Bates set out for the Amazon in 1848 with the aim of “solving the problem of the origin of species”. Yet this enticing story is based on only one sentence. Bates claimed in the preface to his 1863 book that Wallace stated this was the aim of their expedition in an 1847 letter. Bates gave a quotation from the letter. But Wallace himself never endorsed or (...) repeated this story. Many writers have acknowledged that this letter still survives. Yet the wording is different from that quoted by Bates and the letter says nothing of an expedition. It is argued that the sentence given by Bates is not a genuine quotation from this or any other Wallace letter but was modified by Bates to promote his own reputation. More significantly, this leads to the conclusion that there was a very sudden and dramatic shift in the way species were thought of and discussed after Darwin’s Origin of species appeared. Something called “the problem of the origin of species” never occurred before Darwin’s book but exploded in frequency immediately after it. A profound change in how species origins were discussed happened which no one seemed to notice. (shrink)

The theoretical status of ‘niche construction’ in evolution is intensely debated. Here we substantiate the reasons for different interpretations. We consider two concepts of niche construction brought to bear on evolutionary theory; one that emphasizes how niche construction contributes to selection and another that emphasizes how it contributes to development and inheritance. We explain the rationale for claims that selective and developmental niche construction motivate conceptual change in evolutionary biology and the logic of those who reject these claims. Our analysis (...) shows how the contention arises from alternative assumptions regarding the causal independence of the processes that generate variation, differential fitness and inheritance. (shrink)

Se ha impuesto la imagen del código de barras para hacer referencia a una secuencia de ADN mitocondrial que es utilizada para medir la distancia genética entre poblaciones animales. Según la interpretación esencialista de esta analogía, este método de medición serviría, por sí mismo, no solo para la rápida identificación de ejemplares, o muestras fragmentarias, de especies previamente clasificadas, sino también para el descubrimiento de nuevas especies. Los taxónomos integrativos han rechazado este último uso del método del código de barras (...) de ADN, dado que la complejidad biológica impide aplicarlo con precisión en eventos de especiación recientes. Argumentaré, sin embargo, que el método falla por razones conceptuales y no meramente empíricas. Aunque no existiera ese impedimento empírico, el código de barras de ADN no podría ser un método de descubrimiento de especies. (shrink)

In a macroevolutionary timescale, evolvability itself evolves. Lineages are sorted based on their ability to generate adaptive novelties, which leads to the optimization of their genotype-phenotype map. The system of translation of genetic or epigenetic changes to the phenotype may reach significant horizontal and vertical complexity, and may even exhibit certain aspects of learning behaviour. This continuously evolving semiotic system probably enables the origin of complex yet functional and internally compatible adaptations. However, it also has a second, “darker”, side. As (...) was pointed out by several authors, the same process gradually reduces the probability of the origination of significant evolutionary novelties. In a similar way to the evolution of societies, teachings, or languages, in which the growing number of internal linkages gradually solidifies their overall structure and the structure or interpretation of their constitutive elements, the evolutionary potential of lineages decreases during biological evolution. Possible adaptations become limited to small “peripheral” modifications. According to the Frozen Evolution theory, some of the proximate causes of this “macroevolutionary freezing” are more pronounced or present exclusively in sexual lineages. Sorting based on the highest evolvability probably leads to the establishment of certain structural features of complex organisms, e.g. the modular character of their development and morphology. However, modules also “macroevolutionary freeze” whereas the hypothetical “thawing” of modules or their novel adaptive combinations becomes rarer and rarer. Some possible ways out of this dead end include the rearrangement of individual development, e.g. neoteny, radical simplification, i.e. sacculinization, and transition to a higher level of organization, e.g. symbiosis or symbiogenesis. The evolution of evolvability is essentially a biosemiotic process situated at the intersection of the genocentric modern synthesis and the evo-devo-centric extended synthesis. Therefore, evolvability may eventually connect these three not necessarily contradictory approaches. (shrink)

The experimental method is designed to secure the reliable attribution of causal relationships by means of controlled comparison across conditions. Doing so, however, depends upon the reduction of uncertainties and inconsistencies in the process of comparison; and this poses particularly significant challenges for the behavioral and social sciences because they work with human subjects, whose malleability and complexity often interact in unexpected ways with experimental manipulations, thus resulting in unpredictable behavior. Drawing on the Science and Technology Studies perspective and one (...) of our authors’ experiences in experimental work, this paper examines how experimental social scientists manage to establish objectivity and standardization in the face of vagaries arising from working with human subjects. In identifying experimental researchers’ solutions to this challenge, we draw on methodological discussions among applied social scientists as naturally occurring data, through which we show how some seemingly mundane practices play essential roles in extracting patterns out of otherwise unpredictable behaviors in the lab. Closely examining such strategies, we reveal the inherent instabilities in the experimental method when adopted in the social sciences and discuss their methodological implications. In conclusion, we make tentative suggestions for escaping the kinds of methodological impasses which we have identified. (shrink)

Modern evolutionary theory is both a central theory and an integrative framework of the life sciences. This is reflected in the common references to evolution in modern science education curricula and contexts. In fact, evolution is a core idea that is supposed to support biology learning by facilitating the organization of relevant knowledge. In addition, evolution can function as a pivotal link between concepts and highlight similarities in the complexity of biological concepts. However, empirical studies in many countries have for (...) decades identified deficiencies in students’ scientific understanding of evolution mainly focusing on natural selection. Clearly, there are major obstacles to learning natural selection, and we argue that to overcome them, it is essential to address explicitly the general abstract concepts that underlie the biological processes, e.g., randomness or probability. Hence, we propose a two-dimensional framework for analyzing and structuring teaching of natural selection. The first—purely biological—dimension embraces the three main principles variation, heredity, and selection structured in nine key concepts that form the core idea of natural selection. The second dimension encompasses four so-called thresholds, i.e., general abstract and/or non-perceptual concepts: randomness, probability, spatial scales, and temporal scales. We claim that both of these dimensions must be continuously considered, in tandem, when teaching evolution in order to allow development of a meaningful understanding of the process. Further, we suggest that making the thresholds tangible with the aid of appropriate kinds of visualizations will facilitate grasping of the threshold concepts, and thus, help learners to overcome the difficulties in understanding the central theory of life. (shrink)

Evolutionary theory predicts that humans should avoid incest because of the negative effects incest has on individual reproduction: production of defective offspring. Selection for the avoidance of close-kin mating has apparently resulted in a psychological mechanism that promotes voluntary incest avoidance. Most human societies are thought to have rules regulating incest. If incest is avoided, why are social rules constructed to regulate it? This target article suggests that incest rules do not exist primarily to regulate close-kin mating but to regulate (...) inbreeding between more distant kin and sexual relations between affinal relatives. Three evolutionary hypotheses about cousin marriage and affinal kin mating follow from this suggestion: Rules regulating mating between affinal kin are means of paternity protection. Cousin marriage is regulated because, if it occurs, it can concentrate wealth and power within families to the detriment of the powerful positions of rulers in stratified societies and the relatively equal social statuses of most men in egalitarian societies. Tests using the comparative method on a worldwide sample of 129 societies supported the three hypotheses. Two alternative anthropological hypotheses failed to be supported. (shrink)