Costs for switching partners reduce network dynamics but not cooperative behaviour

Social networks represent the structuring of interactions between group members. Above all, many interactions are profoundly cooperative in humans and other animals. In accordance with this natural observation, theoretical work demonstrates that certain network structures favour the evolution of cooperation. Yet, recent experimental evidence suggests that static networks do not enhance cooperative behaviour in humans. By contrast, dynamic networks do foster cooperation. However, costs associated with dynamism such as time or resource investments in finding and establishing new partnerships have been neglected so far. Here, we show that human participants are much less likely to break links when costs arise for building new links. Especially, when costs were high, the network was nearly static. Surprisingly, cooperation levels in Prisoner''s Dilemma games were not affected by reduced dynamism in social networks. We conclude that the mere potential to quit collaborations is sufficient in humans to reach high levels of cooperative behaviour. Effects of self-structuring processes or assortment on the network played a minor role: participants simply adjusted their cooperative behaviour in response to the threats of losing a partner or of being expelled.     

Intercompany Energy Integration

Reusing heat through process integration in heat exchanger networks has long been a key measure for increasing energy efficiency in energy‐intensive industries. Thermal pinch analysis is commonly used for a systematic matching of process streams and thus planning of optimal process integration in large chemical plants. The possible savings increase with the amount of heat and the number of integrated process streams. Therefore co‐ siting of several companies in a symbiotic network opens new opportunities for process integration even in small and medium‐size enterprises (SMEs), but also introduces new challenges. Thermal pinch analysis is extended here to account for piping distances and fluctuations and limited availability of energy flows by adding additional costs for the piping system and a backup utility system in the optimization function. Cooperative game theory is proposed to derive a sharing of savings between the partners of the industrial symbiosis that is optimal for each partner and should prevent partners from leaving the network because of higher benefits in a subgroup or alone. It is argued that knowledge about the optimality of a network for each partner creates trust between the partners that is a necessary base for the long‐term commitment needed in industrial symbioses. An exemplary symbiotic network combining the production of pulp and woody biomass energy carriers is used to illustrate the proposed approaches.     

The resident's dilemma: a female choice model for the evolution of alternative mating strategies in lekking male ruffs (Philomachus pugnax)

Previous models for the evolution of alternative male matingbehavior have virtually ignored the role of female choice. Wepresent a model in which female choice favors the evolutionand maintenance of alternative mating strategies in male ruffs,Philomachus pugnax. Resident male ruffe establish and defendcourts on leks against other residents, while non-territorialsatellite males move between leks and among courts on a lek.Residents appear to actively recruit satellites to their courts,even though satellites may mate with females once there. Residentbehavior toward satellites and data on female behavior suggestthat residents benefit from a satellite's presence due to somefemale preference for mating on co-occupied courts. However,if all residents accept satellites, none gains any relativeadvantage, yet all pay the costs of having satellites on theircourt. We present a game theoretical model that shows that therelative nature of female choice places residents in an evolutionarydilemma with respect to satellite acceptance. Although all residentswould benefit if satellites could be cooperatively excludedfrom leks, the only evolutionarily stable strategy for individualresidents is to defect and accept satellites. The model alsodemonstrates that this "resident's dilemma" likely exists onlyin a local sense, since the failure of residents to cooperativelyexclude satellites from leks need not result in globally lowerpayoffs, due to frequency-dependent selection on the proportionof satellites in the population. Our analysis suggests thatthe resident-satellite relationship in ruffs, despite its obviouscompetitive elements, is fundamentally a cooperative associationfavored by female choice. Female choice has also been proposedas the primary mechanism selecting for male association to formleks in ruffe. In this context, resident-satellite associationsmay be thought of as transitory "leks within a lek     

Lethal and sub‐lethal impacts of respiratory cryptosporidiosis on Red Grouse,a wild gamebird of economic importance

Respiratory cryptosporidiosis was first diagnosed in Red Grouse Lagopus lagopus scotica, the UK subspecies of Willow Ptarmigan, in 2010. In the next 3 years, respiratory infection by Cryptosporidium baileyi had manifested itself in Grouse on half the moors in northern England and 80% of moors in the North Pennine Hills. In this first account of the impact of respiratory cryptosporidiosis on the population dynamics of a wild bird we fitted 111 diseased and 67 healthy Grouse with radio‐transmitters at two North Pennine moors where disease prevalence averaged 8.1% and monitored their survival and fecundity between autumn 2013 and autumn 2015. Six‐month natural survival rates (excluding shooting) were 0.70 in healthy Grouse, but only 0.44 in diseased females, and 0.22 in diseased males. Some 39% of diseased birds died from their infection, whereas 28% of healthy birds were shot. A similar proportion of each group were killed by predators, either by Stoat Mustela erminea or raptors. Diseased females bred 8 days later than healthy females, but clutch size, egg volume and nesting success did not differ in relation to disease status. Productivity was 43% lower among pairs with a diseased member than in healthy pairs, but appeared impaired only if the female was diseased, not the male. Differences in productivity were related to chick survival rather than the proportion of pairs that reared broods, with chick survival being lower in the 10 days after hatching and again when chicks were 20–50 days old. This latter period was when respiratory infection among chicks was first noticed and the onset of infection may have been a contributing factor to higher mortality during this period. Described levels of respiratory infection reduced the number of birds available to shoot in August by 6%, which represented a mean annual loss of £0.9 million in revenue across managed grouse moors. Likely reductions in shoot economics could escalate should prevalence increase. This disease is a welfare concern and potentially a conservation concern, too, should infection cross to other bird species occupying the same moors.     

Evolutionary stability and the rarity of grandmothering

The provision of intergenerational care, via the Grandmother Hypothesis, has been implicated in the evolution of postfertile longevity, particularly in humans. However, if grandmothering does provide fitness benefits, a key question is why has it evolved so infrequently? We investigate this question with a combination of life‐history and evolutionary game theory. We derive simple eligibility and stability thresholds, both of which must be satisfied if intergenerational care is first to evolve and then to persist in a population. As one threshold becomes easier to fulfill, the other becomes more difficult, revealing a conflict between the two. As such, we suggest that, in fact, we should expect the evolution of grandmothering to be rare.     

Ethics,evolution and culture

Recent work in the fields of evolutionary ethics and moral psychology appears to be converging on a single empirically- and evolutionary-based science of morality or ethics. To date, however, these fields have failed to provide an adequate conceptualisation of how culture affects the content and distribution of moral norms. This is particularly important for a large class of moral norms relating to rapidly changing technological or social environments, such as norms regarding the acceptability of genetically modified organisms. Here we suggest that a science of morality/ethics can benefit from adopting a cultural evolution or gene-culture coevolution approach, which treats culture as a second, separate evolutionary system that acts in parallel to biological/genetic evolution. This cultural evolution approach brings with it a set of established theoretical concepts (e.g. different cultural transmission mechanisms) and empirical methods (e.g. evolutionary game theory) that can significantly improve our understanding of human morality.

Neural correlates of economic game playing

The theory of games provides a mathematical formalization of strategic choices, which have been studied in both economics and neuroscience, and more recently has become the focus of neuroeconomics experiments with human and non-human actors. This paper reviews the results from a number of game experiments that establish a unitary system for forming subjective expected utility maps in the brain, and acting on these maps to produce choices. Social situations require the brain to build an understanding of the other person using neuronal mechanisms that share affective and intentional mental states. These systems allow subjects to better predict other players' choices, and allow them to modify their subjective utility maps to value pro-social strategies. New results for a trust game are presented, which show that the trust relationship includes systems common to both trusting and trustworthy behaviour, but they also show that the relative temporal positions of first and second players require computations unique to that role.