Shared intentions and the advance of cumulative culture in hunter-gatherers

It has been hypothesized that the evolution of modern human cognition was catalyzed by the development of jointly intentional modes of behaviour. From an early age (1-2 years), human infants outperform apes at tasks that involve collaborative activity. Specifically, human infants excel at joint action motivated by reasoning of the form "we will do X" (shared intentions), as opposed to reasoning of the form "I will do X [because he is doing X]" (individual intentions). The mechanism behind the evolution of shared intentionality is unknown. Here we formally model the evolution of jointly intentional action and show under what conditions it is likely to have emerged in humans. Modelling the interaction of hunter-gatherers as a coordination game, we find that when the benefits from adopting new technologies or norms are low but positive, the sharing of intentions does not evolve, despite being a mutualistic behaviour that directly benefits all participants. When the benefits from adopting new technologies or norms are high, such as may be the case during a period of rapid environmental change, shared intentionality evolves and rapidly becomes dominant in the population. Our results shed new light on the evolution of collaborative behaviours.Comment: 6 pages, 4 figures, 1 table, Supplementary Information not include

Cheap talk and editorial control

This paper analyzes simple models of editorial control. Starting from the framework developed by Krishna and Morgan (2001a), we analyze 2-sender models of cheap talk where one or more of the senders has the power to veto messages before they reach the receiver. A characterization of the most informative equilibria of such models is given. It is shown that editorial control never aids communication and that for small biases in the senders’ preferences relative to those of the receiver, necessary and sufficient conditions for information transmission to be adversely affected are (i) that the senders have opposed preferences relative to the receiver, and (ii) that both senders have powers of editorial control. It is shown that the addition of further senders beyond two weakly decreases information transmission when senders exercising editorial control are anonymous, and weakly increases information transmission when senders exercising editorial control are observed

Stochastic stability on general state spaces

This paper studies stochastic stability methods applied to processes on general state spaces. This includes settings in which agents repeatedly interact and choose from an uncountable set of strategies. Dynamics exist for which the stochastically stable states differ from those of any reasonable finite discretization. When there are a finite number of rest points of the unperturbed dynamic, sufficient conditions for analogues of results from the finite state space literature are derived and studied. Illustrative examples are given

Coalitions, tipping points and the speed of evolution

This study considers pure coordination games on networks and the waiting time for an adaptive process of strategic change to achieve efficient coordination. Although it is in the interest of every player to coordinate on a single globally efficient norm, coalitional behavior at a local level can greatly slow, as well as hasten convergence to efficiency. For some networks, when one action becomes efficient enough relative to the other, the effect of coalitional behavior changes abruptly from a conservative effect to a reforming effect. These effects are confirmed for a variety of stylized and empirical social networks found in the literature. For coordination games in which the Pareto efficient and risk dominant equilibria differ, polymorphic states can be the only stochastically stable states

Epidemiological studies of inflammatory airway disease in horses

Studies of respiratory disease in different populations of horses were undertaken, including a case control study, using clinically apparent respiratory disease in Thoroughbred racehorses as the case definition. Controls were matched on date and training yard and data were analysed using conditional logistic regression. Disease was statistically associated with several infectious and non-infectious risk factors. Younger horses, those entering training within the last 3 months and those with Actinobacillus/Pasteurella spp. or Mycoplasma felis isolated from the trachea were at increased risk of clinical disease. When all controls with sub-clinical disease were excluded, tracheal Streptococcus zooepidemicus infection was significantly associated with disease. An experimental bacterial vaccine against S. zooepidemicus and Actinobacillus spp. was evaluated for its effect on natural respiratory disease in Welsh Mountain pony foals using a blinded, randomised, controlled trial. Weekly examinations were conducted in 29 ponies, of which 12 received vaccine, 12 received placebo and 5 were untreated. Data were analysed using a multilevel modeling approach, with autoregressive variables to adjust for significant effects of disease in previous time periods. Tracheal infection with S. zooepidemicus was a significant risk factor for aggregated clinical scores and clinical signs of nasal discharge, cough and dyspnoea. There was evidence for a significant dose response between S. zooepidemicus infection and dyspnoea and inflammatory airway disease. Both pony-level and observation-level analyses demonstrated significant variation in clinical scores between ponies with transferrin haplotypes D or F2. Tracheal and nasopharyngeal isolates of S. zooepidemicus from the ponies in the vaccination study were typed by polymerase chain reaction of the hypervariable region of the M-protein (5 possible types) and the 16S-23S RNA gene intergenic spacer (8 possible types). More S. zooepidemicus types were isolated from the trachea than the nasopharynx. There was evidence for clonal succession of types over time and novel S. zooepidemicus types were identified. There were apparent differences in the strength of association of different S. zooepidemicus types with respiratory disease in these ponies during the study period

Not all jellyfish are equal: isotopic evidence for inter- and intraspecific variation in jellyfish trophic ecology

Jellyfish are highly topical within studies of pelagic food-webs and there is a growing realisation that their role is more complex than once thought. Efforts being made to include jellyfish within fisheries and ecosystem models are an important step forward, but our present understanding of their underlying trophic ecology can lead to their oversimplification in these models. Gelatinous zooplankton represent a polyphyletic assemblage spanning >2,000 species that inhabit coastal seas to the deep-ocean and employ a wide variety of foraging strategies. Despite this diversity, many contemporary modelling approaches include jellyfish as a single functional group feeding at one or two trophic levels at most. Recent reviews have drawn attention to this issue and highlighted the need for improved communication between biologists and theoreticians if this problem is to be overcome. We used stable isotopes to investigate the trophic ecology of three co-occurring scyphozoan jellyfish species (Aurelia aurita, Cyanea lamarckii and C. capillata) within a temperate, coastal food-web in the NE Atlantic. Using information on individual size, time of year and δ 13 C and δ 15 N stable isotope values, we examined: (1) whether all jellyfish could be considered as a single functional group, or showed distinct inter-specific differences in trophic ecology; (2) Were size-based shifts in trophic position, found previously in A. aurita, a common trait across species?; (3) When considered collectively, did the trophic position of three sympatric species remain constant over time? Differences in δ 15 N (trophic position) were evident between all three species, with size-based and temporal shifts in δ 15 N apparent in A. aurita and C. capillata. The isotopic niche width for all species combined increased throughout the season, reflecting temporal shifts in trophic position and seasonal succession in these gelatinous species. Taken together, these findings support previous assertions that jellyfish require more robust inclusion in marine fisheries or ecosystem models

Proteomics of Carbon Fixation Energy Sources in Halothiobacillus neapolitanus

Through the use of proteomics, it was uncovered that the autotrophic, aerobic purple sulfur bacterium Halothiobacillus neapolitanus displays changes in cellular levels of portions of its carbon dioxide uptake and fixation mechanisms upon switch from bicarbonate to CO2(g) as carbon source. This includes an increase in level of a heterodimeric bicarbonate transporter along with a potential switch between form I and form II of RubisCO. Additional changes are seen in several sulfur oxidation pathways, which may indicate a link between sulfur oxidation pathways as an energy source and carbon uptake/fixation mechanisms

An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra

Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs, but is within reach for only a limited sample of nearby, bright stars. We use interferometrically-measured radii, bolometric luminosities, and effective temperatures to develop new empirical calibrations based on low-resolution, near-infrared spectra. We use H-band Mg and Al features to derive calibrations for effective temperature, radius and log luminosity; the standard deviations in the residuals of our best fits are, respectively, 73K, 0.027Rsun, and 0.049 dex (11% error on luminosity). These relationships are valid for mid K to mid M dwarf stars, roughly corresponding to temperatures between 3100 and 4800K. We apply our calibrations to M dwarfs targeted by the MEarth transiting planet survey and to the cool Kepler Objects of Interest (KOIs). We independently validate our calibrations by demonstrating a clear relationship between our inferred parameters and the absolute K magnitudes of the MEarth stars, and we identify objects with magnitudes too bright for their estimated luminosities as candidate multiple systems. We also use our inferred luminosities to address the applicability of near-infrared metallicity calibrations to mid and late M dwarfs. The temperatures we infer for the KOIs agree remarkably well with those from the literature; however, our stellar radii are systematically larger than those presented in previous works that derive radii from model isochrones. This results in a mean planet radius that is 15% larger than one would infer using the stellar properties from recent catalogs. Our results confirm those of previous in-depth studies of Kepler-42, Kepler-45, and Kepler-186.Comment: Accepted to ApJ. Tables 4 and 5, and machine readable versions of Tables 5 and 7 are available in the ApJ journal articl