The Agential View of Misfortune.

In many traditional, small-scale societies, death and other misfortunes are commonly explained as a result of others' malign occult agency. Here, we call this family of epistemic tendencies "the agential view of misfortune." After reviewing several ethnographic case studies that illustrate this view, we argue that its origins and stability are puzzling from an evolutionary perspective. Not only is the agential view of misfortune false; it imposes costs on individuals and social groups that seem to far outweigh whatever benefits the view might provide. We thus doubt that the agential view of misfortune is explainable in terms of adaptive effects. However, neither does it seem readily explainable as a consequence of belief formation strategies that are on the whole adaptive (as is plausibly the case for certain other of our false beliefs, including some that are costly). Accordingly, we contend that the commonness of the agential view of misfortune demands a special evolutionary explanation of some kind. We provide a partial explanation of this phenomenon by highlighting the adaptive benefits that often flow to occult specialists in environments where the agential view of misfortune is entrenched. What this does not explain, however, is the general lack of resistance we observe in response to occultists' exploitative behaviours over (cultural) evolutionary timescales. We conclude by canvassing a few possible explanations for this puzzling lack of resistance, and while we commit ourselves to none, we do find one option more promising than the others.

Mind the gap: Why is there no general purpose ideographic system?

Morin has identified an intriguing puzzle about human communication systems, and one element of the solution: Inscriptional sign systems pose more coordination problems, making sender/receiver coadaptation more difficult. But I reject his view of written language, concluding that inscriptional sign systems can be generalist. The upshot is a cost-based proposal about why generalist ideographic systems are essentially unknown.

Foragers and Their Tools: Risk, Technology and Complexity.

The subsistence technology of forager communities has varied greatly over space and time. This paper (i) reviews briefly the main causal factors the literature identifies as responsible for this variation; (ii) analyzes in some detail the most prominent idea in the literature on spatial variation:Complex technology is an adaptive response to elevated risks of subsistence failure; (iii) it argues that the alleged empirical support for this hypothesis depends on dubious proxies of risk; (iv) it argues that it fails to explain the subsistence technologies of desert foragers, who generally live with simple technologies in high-risk environments; (v) it offers an alternative analysis, based on the reduced opportunity costs of complex technologies in highly seasonal environments, on the high value of typical forager targets in those environments and their relatively predictable location in space and time; and (v) the paper concludes with a conjecture about the role of environmental variation in toolkit change over deep time.

Veiled agency? Children, innovation and the archaeological record.

Children and subadults were obviously part of ancient human communities, and almost certainly, in important ways their activities were distinctive; they did not routinely act like scaled down adults. Yet their presence was quite cryptic, but not entirely hidden. Their lives and acts did leave traces, although these tend to be be fragile, ambiguous and fast-fading. In addition to pursuing the methodological issues posed by the detection of subadult lives, this special issue raises important questions about the role of children, and their willingness to experiment and play, on innovation. It is true that ethnographically known forager children are almost certainly more autonomous, experimental and adventurous than WEIRD children, and this was probably true of the young foragers of the early Holocene and late Pleistocene too. Their greater willingness to experiment probably fuelled a supply of variation, and perhaps occasionally adaptation as well, especially finding new uses for existing materials. Much more certainly, innovations tend to be noted, taken up and spread by adolescents. They were vectors of change, even if perhaps only rarely initiators of change.

Innovation, life history and social networks in human evolution.

There is a famous puzzle about the first 3 million years of archaeologically visible human technological history. The pace of change, of innovation and its uptake, is extraordinarily slow. In particular, the famous handaxes of the Acheulian technological tradition first appeared about 1.7 Ma, and persisted with little change until about 800 ka, perhaps even longer. In this paper, I will offer an explanation of that stasis based in the life history and network characteristics that we infer (on phylogenetic grounds) to have characterized earlier human species. The core ideas are that (i) especially in earlier periods of hominin evolution, we are likely to find archaeological traces only of widespread and persisting technologies and practices; (ii) the record is not a record of the rate of innovation, but the rate of innovations establishing in a landscape; (iii) innovations are extremely vulnerable to stochastic loss while confined to the communities in which they are made and established; (iv) the export of innovation from the local group is sharply constrained if there is a general pattern of hostility and suspicion between groups, or even if there is just little contact between adults of adjoining groups. That pattern is typical of great apes and likely, therefore, to have characterized at least early hominin social lives. Innovations are unlikely to spread by adult-to-adult interactions across community boundaries. (v) Chimpanzees and bonobos are characterized by male philopatry and subadult female dispersal; that is, therefore, the most likely early hominin pattern. If so, the only innovations at all likely to expand beyond the point of origin are those acquired by subadult females, and ones that can be expressed by those females, at high enough frequency and salience for them to spread, in the bands that the females join. These are very serious filters on the spread of innovation. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

Afterword: Tough Questions; Hard Problems; Incremental Progress.

The papers in this issue have specific and focused targets that are essential for making incremental progress on the very difficult problem of identifying the coevolutionary interactions of cognition and culture. The purpose of this paper is to discern the shape of a few of the large problems that loom over these more narrowly focussed papers, and to explain and assess the ways these papers contribute to their solution. The background problems described are (a) the character of the selective interactions between the evolution of culture and of cognition; (b) the special features of cumulative cultural evolution; and (c) the place of language in an account of cognition-culture coevolution. The paper ends with some reflections on the extraordinarily difficult challenge of testing scenarios in this field.

Exploring cycad foliage as an archive of the isotopic composition of atmospheric nitrogen.

Molecular nitrogen (N2 ) constitutes the majority of Earth's modern atmosphere, contributing ~0.79 bar of partial pressure (pN2 ). However, fluctuations in pN2 may have occurred on 107 -109  year timescales in Earth's past, perhaps altering the isotopic composition of atmospheric nitrogen. Here, we explore an archive that may record the isotopic composition of atmospheric N2 in deep time: the foliage of cycads. Cycads are ancient gymnosperms that host symbiotic N2 -fixing cyanobacteria in modified root structures known as coralloid roots. All extant species of cycads are known to host symbionts, suggesting that this N2 -fixing capacity is perhaps ancestral, reaching back to the early history of cycads in the late Paleozoic. Therefore, if the process of microbial N2 fixation records the δ15 N value of atmospheric N2 in cycad foliage, the fossil record of cycads may provide an archive of atmospheric δ15 N values. To explore this potential proxy, we conducted a survey of wild cycads growing in a range of modern environments to determine whether cycad foliage reliably records the isotopic composition of atmospheric N2 . We find that neither biological nor environmental factors significantly influence the δ15 N values of cycad foliage, suggesting that they provide a reasonably robust record of the δ15 N of atmospheric N2 . Application of this proxy to the record of carbonaceous cycad fossils may not only help to constrain changes in atmospheric nitrogen isotope ratios since the late Paleozoic, but also could shed light on the antiquity of the N2 -fixing symbiosis between cycads and cyanobacteria.

Moral externalisation fails to scale.

We argue that Stanford's picture of the evolution of externalised norms is plausible mostly because of the idealisations implicit in his defence of it. Once we take into account plausible amounts of normative disagreement, plausible amounts of error and misunderstanding, and the knock-on consequences of shunning, it is plausible that Stanford under-counts the costs of externalisation.

Humans as model organisms.

Like every other species, our species is the result of descent with modification under the influence of natural selection; a tip in an increasingly large and deep series of nested clades, as we trace its ancestry back to increasingly remote antecedents. As a consequence of shared history, our species has much in common with many others; as a consequence of its production by the general mechanisms of evolution, our species carries information about the mechanisms that shaped other species as well. For reasons unconnected to biological theory, we have far more information about humans than we do about other species. So in principle and in practice, humans should be usable as model organisms, and no one denies the truth of this for mundane physical traits, though harnessing human data for more general questions proves to be quite challenging. However, it is also true that human cognitive and behavioural characteristics, and human social groups, are apparently radically unlike those of other animals. Humans are exceptional products of evolution and perhaps that makes them an unsuitable model system for those interested in the evolution of cooperation, complex cognition, group formation, family structure, communication, cultural learning and the like. In all these respects, we are complex and extreme cases, perhaps shaped by mechanisms (like cultural evolution or group selection) that play little role in other lineages. Most of the papers in this special issue respond by rejecting or downplaying exceptionalism. I argue that it can be an advantage: understanding the human exception reveals constraints that have restricted evolutionary options in many lineages.

In defence of story-telling.

We argue that narratives are central to the success of historical reconstruction. Narrative explanation involves tracing causal trajectories across time. The construction of narrative, then, often involves postulating relatively speculative causal connections between comparatively well-established events. But speculation is not always idle or harmful: it also aids in overcoming local underdetermination by forming scaffolds from which new evidence becomes relevant. Moreover, as our understanding of the past's causal milieus become richer, the constraints on narrative plausibility become increasingly strict: a narrative's admissibility does not turn on mere logical consistency with background data. Finally, narrative explanation and explanation generated by simple, formal models complement one another. Where models often achieve isolation and precision at the cost of simplification and abstraction, narratives can track complex changes in a trajectory over time at the cost of simplicity and precision. In combination both allow us to understand and explain highly complex historical sequences.

From mechanisms to function: an integrated framework of animal innovation.

Animal innovations range from the discovery of novel food types to the invention of completely novel behaviours. Innovations can give access to new opportunities, and thus enable innovating agents to invade and create novel niches. This in turn can pave the way for morphological adaptation and adaptive radiation. The mechanisms that make innovations possible are probably as diverse as the innovations themselves. So too are their evolutionary consequences. Perhaps because of this diversity, we lack a unifying framework that links mechanism to function. We propose a framework for animal innovation that describes the interactions between mechanism, fitness benefit and evolutionary significance, and which suggests an expanded range of experimental approaches. In doing so, we split innovation into factors (components and phases) that can be manipulated systematically, and which can be investigated both experimentally and with correlational studies. We apply this framework to a selection of cases, showing how it helps us ask more precise questions and design more revealing experiments.

Adaptable individuals and innovative lineages.

This paper suggests (i) that while work on animal innovation has made good progress in understanding some of the proximate mechanisms and selective regimes through which innovation emerges, it has somewhat neglected the role of the social environment of innovation; a neglect manifest in the fact that innovation counts are almost always counts of resource-acquisition innovations; the invention of social tools is rarely considered. The same is true of many experimental projects, as these typically impose food acquisition tasks on their experimental subjects. (ii) That neglect is important, because innovations often pose collective action problems; the hominin species were technically innovative because they were also socially adaptable. (iii) In part for this reason, there remains a disconnect between research on hominin innovation and research on animal innovation. (iv) Finally, the paper suggests that there is something of a disconnect between the theoretical work on innovation in hominin evolution (based on theories of cultural evolution) and the experimental tradition on human innovation. That disconnect is largely due to the theoretical work retreating from strong claims about the proximate mechanisms of human cultural accumulation.

The extended evolutionary synthesis: its structure, assumptions and predictions.

Scientific activities take place within the structured sets of ideas and assumptions that define a field and its practices. The conceptual framework of evolutionary biology emerged with the Modern Synthesis in the early twentieth century and has since expanded into a highly successful research program to explore the processes of diversification and adaptation. Nonetheless, the ability of that framework satisfactorily to accommodate the rapid advances in developmental biology, genomics and ecology has been questioned. We review some of these arguments, focusing on literatures (evo-devo, developmental plasticity, inclusive inheritance and niche construction) whose implications for evolution can be interpreted in two ways­one that preserves the internal structure of contemporary evolutionary theory and one that points towards an alternative conceptual framework. The latter, which we label the 'extended evolutionary synthesis' (EES), retains the fundaments of evolutionary theory, but differs in its emphasis on the role of constructive processes in development and evolution, and reciprocal portrayals of causation. In the EES, developmental processes, operating through developmental bias, inclusive inheritance and niche construction, share responsibility for the direction and rate of evolution, the origin of character variation and organism-environment complementarity. We spell out the structure, core assumptions and novel predictions of the EES, and show how it can be deployed to stimulate and advance research in those fields that study or use evolutionary biology.

Language, gesture, skill: the co-evolutionary foundations of language.

This paper defends a gestural origins hypothesis about the evolution of enhanced communication and language in the hominin lineage. The paper shows that we can develop an incremental model of language evolution on that hypothesis, but not if we suppose that language originated in an expansion of great ape vocalization. On the basis of the gestural origins hypothesis, the paper then advances solutions to four classic problems about the evolution of language: (i) why did language evolve only in the hominin lineage? (ii) why is language use an evolutionarily stable form of informational cooperation, despite the fact that hominins have diverging evolutionary interests? (iii) how did stimulus independent symbols emerge? (iv) what were the origins of complex, syntactically organized symbols? The paper concludes by confronting two challenges: those of testability and of explaining the gesture-to-speech transition; crucial issues for any gestural origins hypothesis.

Cause and effect in biology revisited: is Mayr's proximate-ultimate dichotomy still useful?

Fifty years ago, Ernst Mayr published a hugely influential paper on the nature of causation in biology, in which he distinguished between proximate and ultimate causes. Mayr equated proximate causation with immediate factors (for example, physiology) and ultimate causation with evolutionary explanations (for example, natural selection). He argued that proximate and ultimate causes addressed different questions and were not alternatives. Mayr's account of causation remains widely accepted today, with both positive and negative ramifications. Several current debates in biology (for example, over evolution and development, niche construction, cooperation, and the evolution of language) are linked by a common axis of acceptance/rejection of Mayr's model of causation. We argue that Mayr's formulation has acted to stabilize the dominant evolutionary paradigm against change but may now hamper progress in the biological sciences.

From hominins to humans: how sapiens became behaviourally modern.

This paper contributes to a debate in the palaeoarchaeological community about the major time-lag between the origin of anatomically modern humans and the appearance of typically human cultural behaviour. Why did humans take so long--at least 100 000 years--to become 'behaviourally modern'? The transition is often explained as a change in the intrinsic cognitive competence of modern humans: often in terms of a new capacity for symbolic thought, or the final perfection of language. These cognitive breakthrough models are not satisfactory, for they fail to explain the uneven palaeoanthropological record of human competence. Many supposed signature capacities appear (and then disappear) before the supposed cognitive breakthrough; many of the signature capacities disappear again after the breakthrough. So, instead of seeing behavioural modernity as a simple reflection of a new kind of mind, this paper presents a niche construction conceptual model of behavioural modernity. Humans became behaviourally modern when they could reliably transmit accumulated informational capital to the next generation, and transmit it with sufficient precision for innovations to be preserved and accumulated. In turn, the reliable accumulation of culture depends on the construction of learning environments, not just intrinsic cognitive machinery. I argue that the model is (i) evolutionarily plausible: the elements of the model can be assembled incrementally, without implausible selective scenarios; (ii) the model coheres with the broad palaeoarchaeological record; (iii) the model is anthropologically and ethnographically plausible; and (iv) the model is testable, though only in coarse, preliminary ways.

The tale of the finch: adaptive radiation and behavioural flexibility.

Darwin's finches are a classic example of adaptive radiation. The ecological diversity of the Galápagos in part explains that radiation, but the fact that other founder species did not radiate suggests that other factors are also important. One hypothesis attempting to identify the extra factor is the flexible stem hypothesis, connecting individual adaptability to species richness. According to this hypothesis, the ancestral finches were flexible and therefore able to adapt to the new and harsh environment they encountered by exploiting new food types and developing new foraging techniques. Phenotypic variation was initially mediated by learning, but genetic accommodation entrenched differences and supplemented them with morphological adaptations. This process subsequently led to diversification and speciation of the Darwin's finches. Their current behaviour is consistent with this hypothesis as these birds use unusual resources by extraordinary means. In this paper, we identify cognitive capacities on which flexibility and innovation depend. The flexible stem hypothesis predicts that we will find high levels of these capacities in all species of Darwin's finches (not just those using innovative techniques). Here, we test that prediction, and find that while most of our data are in line with the flexible stem hypothesis, some are in tension with it.