Human cooperation is highly unusual. We live in large groups composed mostly of non-relatives. Evolutionists have proposed a number of explanations for this pattern, including cultural group selection and extensions of more general processes such as reciprocity, kin selection, and multi-level selection acting on genes. Evolutionary processes are consilient; they affect several different empirical domains, such as patterns of behavior and the proximal drivers of that behavior. In this target article, we sketch the evidence from five domains that bear on the explanatory adequacy of cultural group selection and competing hypotheses to explain human cooperation. Does cultural transmission constitute an inheritance system that can evolve in a Darwinian fashion? Are the norms that underpin institutions among the cultural traits so transmitted? Do we observe sufficient variation at the level of groups of considerable size for group selection to be a plausible process? Do human groups compete, and do success and failure in competition depend upon cultural variation? Do we observe adaptations for cooperation in humans that most plausibly arose by cultural group selection? If the answer to one of these questions is "no," then we must look to other hypotheses. We present evidence, including quantitative evidence, that the answer to all of the questions is "yes" and argue that we must take the cultural group selection hypothesis seriously. If culturally transmitted systems of rules (institutions) that limit individual deviance organize cooperation in human societies, then it is not clear that any extant alternative to cultural group selection can be a complete explanation.Keywords: competition; culture; evolution; group selection; heritable variation; institutions; norms BEHAVIORAL AND BRAIN SCIENCES (2016) KARL FROST is a Ph.D. candidate in Ecology at the University of California, Davis. He researches the cultural evolution of prosociality via religion and ritual practices, using behavioral experiments, gene-culture coevolution models, and field research in Canada looking at environmental activism in the face of the tar sands oil industry and an antagonistic government. He also directs the Body Research Physical Theater and is interested in cross-cultural exchange of theater practice as theater anthropology and arts-science fusion.

ABSTRACT. A central goal of most sustainable agriculture programs is to encourage growers to adopt practices that jointly provide economic, environmental, and social benefits. Using surveys of outreach professionals and wine grape growers, we quantify the perceived costs and benefits of sustainable viticulture practices recommended by sustainability outreach and certification programs. We argue that the mix of environmental benefits, economic benefits, and economic costs determine whether or not a particular practice involves decisions about innovation or cooperation. Decision making is also affected by the overall level of knowledge regarding different practices, and we show that knowledge gaps are an increasing function of cost and a decreasing function of benefits. How different practices are related to innovation and cooperation has important implications for the design of sustainability outreach programs. Cooperation, innovation, and knowledge gaps are issues that are likely to be relevant for the resilience and sustainability of many different types of social-ecological systems.

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Abstract. Drought is a global issue that is exacerbated by climate change and increasing anthropogenic water demands. The recent occurrence of drought in California provides an important opportunity to examine drought response across ecosystem classes (forests, shrublands, grasslands, and wetlands), which is essential to understand how climate influences ecosystem structure and function. We quantified ecosystem resistance to drought by comparing changes in satellite-derived estimates of water-use efficiency (WUE = net primary productivity [NPP]/evapotranspiration [ET]) under normal (i.e., baseline) and drought conditions (ΔWUE = WUE 2014 − baseline WUE). With this method, areas with increasing WUE under drought conditions are considered more resilient than systems with declining WUE. Baseline WUE varied across California (0.08 to 3.85 g C/mm H 2 O) and WUE generally increased under severe drought conditions in 2014. Strong correlations between ΔWUE, precipitation, and leaf area index (LAI) indicate that ecosystems with a lower average LAI (i.e., grasslands) also had greater C-uptake rates when water was limiting and higher rates of carbon-uptake efficiency (CUE = NPP/LAI) under drought conditions. We also found that systems with a baseline WUE ≤ 0.4 exhibited a decline in WUE under drought conditions, suggesting that a baseline WUE ≤ 0.4 might be indicative of low drought resistance. Drought severity, precipitation, and WUE were identified as important drivers of shifts in ecosystem classes over the study period. These findings have important implications for understanding climate change effects on primary productivity and C sequestration across ecosystems and how this may influence ecosystem resistance in the future.

Social learning, learning from others, has value in extending knowledge about farm management through networks of growers. Exactly how much value depends on the structure of the networks. We employed social network analysis to study knowledge networks and social learning in three American Viticulture Areas in California: Central Coast, Lodi and Napa Valley. In a survey, growers confirmed that experiential and social learning are more useful for accessing information about farm management than formal learning. UC Agriculture and Natural Resources Cooperative Extension (UCCE) was found to be well positioned to access and spread knowledge through the grower networks but a bottleneck exists -many knowledge-sharing relationships and relatively few staff. We also found that grower participation in traditional outreach activities, e.g., meetings and demonstrations, is a strong predictor of their number of knowledgesharing relationships, so UCCE and other agricultural support organizations have an important role to play in strengthening networks. Several network-smart extension strategies might help alleviate the bottleneck and rewire networks to more efficiently connect those with questions to those with solutions.A griculture is a knowledgeintensive industry. Therefore, developing new and innovative extension strategies is among the most pressing challenges facing contemporary agriculture (Pretty et al. 2010). Studies have highlighted the value of social learning (people learning from one another), and social learning is considered a critical pathway for extending knowledge about farm management (Pretty and Chambers 2003;Roling and Wagemakers 1998;Warner 2007a). Compared to when they were established in the late 19th century, today's extension systems are more complex, dynamic and networked, and the work of extension may benefit by capitalizing on the network structure of the modern knowledge system (Lubell et al. 2014).Elsewhere, we have shown a positive relationship between growers' number of knowledge-sharing relationships and their adoption of beneficial management practices (Hoffman 2013). However, before Cooperative Extension and other agricultural support organizations (e.g., commissions, marketing orders, voluntary grower associations) can develop extension strategies that harness the natural process of social learning, we must first understand the structure of these knowledge networks and identify leverage points that can rewire the network to connect those with solutions to those with questions.The objective of our research was to find a scientific basis on which networksmart extension strategies can be based. We employed social network analysis (Wasserman and Faust 1994) to study knowledge networks in three American Viticulture Areas (AVAs) in California: Central Coast, Lodi and Napa Valley. We compared the usefulness of social learning to that of two other learning pathways: experiential learning and formal learning. The three knowledge networks in the AVAs were modeled to identify growers and outreach pro...