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Item Degrees of Separation, Social Learning, and the Evolution of Cooperation in a Small-World Network(Journal of Artificial Societies and Social Simulation, 2015) Seltzer, Nicholas; Smirnov, OlegWe analyze a novel agent-based model of a social network in which agents make contributions to others conditional upon the social distance, which we measure in terms of the "degrees of separation" between the two players. On the basis of a simple imitation model, the emerging strategy profile is characterized by high levels of cooperation with those who are directly connected to the agent and lower but positive levels of cooperation with those who are indirectly connected to the agent. Increasing maximum interaction distance decreases cooperation with close neighbors but increases cooperation with distant neighbors for a net negative effect. On the other hand, allowing agents to learn and imitate socially distant neighbors increases cooperation for all types of interaction. Combining greater interaction distance with greater learning distance leads to a positive change in the total social welfare produced by the agents' contributions.Item Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen(Lithosphere, 2019) Zuza, Andrew; Wu, Chen; Wang, Zengzhen; Levy, Drew A.; Li, Bing; Xiong, Xiaosong; Chen, XuanhuaThe Cenozoic Qilian Shan thrust belt is the northern margin of the Tibetan Plateau, which developed in part due to progressive India-Asia convergence during Himalayan-Tibetan orogeny. Available geologic observations suggest that this thrust belt started deforming shortly after initial India-Asia collision at 60-55 Ma, and thus its kinematic development is intrinsically related to the construction and evolution of the Tibetan Plateau. Here, we present new field observations from a geologic traverse across the Qilian Shan to elucidate the style of deformation across the active thrust belt. In particular, we infer protracted out-of-sequence deformation here that is consistent with this thrust system remaining a stationary northern boundary to the Tibetan Plateau since the early Cenozoic. We present a lithosphere-scale model for this region that highlights the following: (1) coupled distributed crustal shortening and underthrusting of the North China craton beneath Tibet, which explains the spatial and temporal distribution of observed crustal shortening and thickness, (2) this underthrusting exploited the south-dipping early Paleozoic Qilian suture paleo-subduction melange channel, and (3) development of a lower-crustal duplex at the lithospheric underthrusting ramp. This last inference can explain the relatively high elevation, low relief, and thickened crust of the central Qilian Shan, as well as the comparative aseismicity of the region, which experiences fewer earthquakes due to less upper-crustal faulting. Both the northern and southern margins of the Himalayan-Tibetan orogen appear to have developed similarly, with continental underthrusting and crustal-scale imbrication and duplexing, despite vastly different climatic and plate-velocity boundary conditions, which suggests that the orogen-scale architecture of the thrust belt is controlled by neither of these forcing mechanisms. Instead, strength anisotropies of the crust probably control the kinematics and style of deformation, including the development of northern Tibet, where thrust systems are concentrated along pre-Cenozoic suture zones.Item The Evolution of Tribalism: A Social-Ecological Model of Cooperation and Inter-group Conflict under Pastoralism(Journal of Artificial Societies and Social Simulation, 2019) Seltzer, Nicholas A.This study investigates a possible nexus between inter-group competition and intra-group cooperation, which may be called "tribalism." Building upon previous studies demonstrating a relationship between the environment and social relations, the present research incorporates a social-ecological model as a mediating factor connecting both individuals and communities to the environment. Cyclical and non-cyclical fluctuation in a simple, two-resource ecology drive agents to adopt either "go-it-alone" or group-based survival strategies via evolutionary selection. Novelly, this simulation employs a multilevel selection model allowing group-level dynamics to exert downward selective pressures on individuals' propensity to cooperate within groups. Results suggest that cooperation and inter-group conflict are co-evolved in a triadic relationship with the environment. Resource scarcity increases inter-group competition, especially when resources are clustered as opposed to widely distributed. Moreover, the tactical advantage of cooperation in the securing of clustered resources enhanced selective pressure on cooperation, even if that implies increased individual mortality for the most altruistic warriors. Troubling, these results suggest that extreme weather, possibly as a result of climate change, could exacerbate conflict in sensitive, weather-dependent social-ecologies - especially places like the Horn of Africa where ecologically sensitive economic modalities overlap with high-levels of diversity and the wide- availability of small arms. As well, global development and foreign aid strategists should consider how plans may increase the value of particular locations where community resources are built or aid is distributed, potentially instigating tribal conflict. In sum, these factors, interacting with pre-existing social dynamics dynamics, may heighten inter-ethnic or tribal conflict in pluralistic but otherwise peaceful communities.Item THE FATE OF LABOR AFTER REGIME CHANGE: Lessons From Post-Communist Poland and Post-Apartheid South Africa For Tunisia's Nobel-Prize Winning Unions(2018-08-18) Hartshorn, Ian; Sil, RudraWherever labor has played a significant role in bringing about regime change, there may be opportunities to join in the post-authoritarian ruling coalition in the hopes of consolidating its influence. This article examines the long-term risks and unanticipated consequences of giving in to this temptation by comparing post-communist Poland and post-apartheid South Africa, where the leading trade union federations became weaker and more divided as their political allies pushed forward with economic liberalization. Tunisia's trade unions, awarded the 2015 Nobel Peace Prize for their contribution to a stable transition after the "Arab Spring," face the risk of going down the same path should they continue to view themselves as partners of the new governing elite, which has already signaled its intention of pursuing further liberalization.