Stefan Linquist

Considerable variation exists not only in the kinds of transposable elements (TEs) occurring within the genomes of different species, but also in their abundance and distribution. Noting a similarity to the assortment of organisms among ecosystems, some researchers have called for an ecological approach to the study of transposon dynamics. However, there are several ways to adopt such an approach, and it is sometimes unclear what an ecological perspective will add to the existing co-evolutionary framework for explaining transposon-host interactions. This review aims to clarify the conceptual foundations of transposon ecology in order to evaluate its explanatory prospects. We begin by identifying three unanswered questions regarding the abundance and distribution of TEs that potentially call for an ecological explanation. We then offer an operational distinction between evolutionary and ecological approaches to these questions. By determining the amount of variance in transposon abundance and distribution that is explained by ecological and evolutionary factors, respectively, it is possible empirically to assess the prospects for each of these explanatory frameworks. To illustrate how this methodology applies to a concrete example, we analyzed whole-genome data for one set of distantly related mammals and another more closely related group of arthropods. Our expectation was that ecological factors are most informative for explaining differences among individual TE lineages, rather than TE families, and for explaining their distribution among closely related as opposed to distantly related host genomes. We found that, in these data sets, ecological factors do in fact explain most of the variation in TE abundance and distribution among TE lineages across less distantly related host organisms. Evolutionary factors were not significant at these levels. However, the explanatory roles of evolution and ecology become inverted at the level of TE families or among more distantly related genomes. Not only does this example demonstrate the utility of our distinction between ecological and evolutionary perspectives, it further suggests an appropriate explanatory domain for the burgeoning discipline of transposon ecology. The fact that ecological processes appear to be impacting TE lineages over relatively short time scales further raises the possibility that transposons might serve as useful model systems for testing more general hypotheses in ecology.

The culture of honour hypothesis offers a compelling example of how human psychology differentially adapts to pastoral and horticultural environments. However, there is disagreement over whether this pattern is best explained by a memetic, evolutionary psychological, dual inheritance, or niche construction model. I argue that this disagreement stems from two shortcomings: lack of clarity about the theoretical commitments of these models and inadequate comparative data for testing them. To resolve the first problem, I offer a theoretical framework for deriving competing predictions from each of the four models. In particular, this involves a novel interpretation of the difference between dual inheritance theory and cultural niche construction. I then illustrate a strategy for testing their predictions using data from the Human Relations Area File. Empirical results suggest that the aggressive psychological phenotype typically associated with honour culture is more common among pastoral societies than among horticultural societies. Theoretical considerations suggest that this pattern is best explained as a case of cultural niche construction

Lawton’s contingency thesis states that there are no useful generalizations at the level of ecological communities because these systems are especially prone to contingent historical events. I argue that this influential thesis has been grounded on the wrong kind of evidence. CT is best understood in Woodward’s terms as a claim about the instability of certain causal dependencies across different background conditions. A recent distinction between evolution and ecology reveals what an adequate test of Lawton’s thesis would look like. To date, CT remains untested. But developments in genome and molecular ecology point in a promising direction.

A common objection to adaptationist accounts of human emotions is that they ignore the influence of culture. If complex emotions like guilt, shame and romantic jealousy are largely culturally determined, how could they be biological adaptations? Dual inheritance models of gene/culture coevolution provide a potential answer to this question. If complex emotions are developmentally ‘scaffolded' by norms that are transmitted from parent to offspring with reasonably high fidelity, then these emotions can evolve to promote individual reproductive interests. This paper draws on case studies of emotional development to illustrate how complex emotions satisfy these conditions. Many of the norms and parenting strategies influencing emotional development are absorbed during the early stages of life when a child is in primary contact with its parents and before the onset of complex cognition. These conditions make it likely that emotion-governing norms are transmitted vertically and with relatively little cognitive ‘contamination'. ‡Thanks to Mark Colyvan, Paul Griffiths, Alexander Rosenberg, and John Wilkins for helpful comments on previous drafts. †To contact the author, please write to: Department of Philosophy, University of Queensland, Brisbane, Queensland 4072, Australia; e-mail: [email protected].

Several recent criticisms of the somatic marker hypothesis (SMH) identify multiple ambiguities in the way it has been formulated by its chief proponents. Here we provide evidence that this hypothesis has also been interpreted in various different ways by the scientific community. Our diagnosis of this problem is that SMH lacks an adequate computational-level account of practical decision making. Such an account is necessary for drawing meaningful links between neurological- and psychological-level data. The paper concludes by providing a simple, five-step model of practical decision making. Recasting SMH in terms of this model generates more precise and empirically tractable computational-level hypotheses about the various ways that somatic markers might influence practical decisions.