Data_Sheet_1_Behavioral Specialization During the Neolithic—An Evolutionary Model.PDF

The emergence of agriculture and complex societies during the Near Eastern Neolithic opened a new era in human evolution. Food production seriously affected the ecological environment, and societies answered this challenge with large-scale division of labor and specialization. In this paper we study this transition with an individual based model. Our model captures the connections between the appearance of agriculture, the social division of labor, and human behavioral diversity. Our two main settings are different habitats: in the pre-Neolithic habitat, resources fluctuated in time and there was no large-scale food storage. In the Neolithic habitat active food production resulted in economic surplus. We consider a sexually reproducing social group, in which individuals solve different tasks for survival. We assume that the task-solving effectiveness has a partial genetic basis but also improves with experience and learning. Since different tasks can require somewhat different skills, we assume trade-offs between genetic propensities for different tasks. Individuals are born with inherited task-choice strategies that they can improve by imitating more successful peers. We show that for the Neolithic case, both phenotypic specialization (task choice strategy) and the emergence of genetic polymorphism are possible, as long as scarcer goods are more valuable. As the number of tasks increases, specialization can evolve only in very large groups. Although phenotypic specialization often emerges in our model, the emergence of genetic polymorphism requires strong assortativity during both imitation and mate choice. In sum, our model shows that if an economic surplus becomes available, behavioral specialization and large-scale division of labor are likely to appear. Thus, our model can help understanding certain aspects of the Neolithic transition, and may have implications for the present genetic polymorphism, too.近东新石器时代农业与复杂社会的出现，开启了人类演化的新纪元。粮食生产严重冲击了生态环境，人类社会则通过大规模劳动分工与专业化来应对这一挑战。本文采用基于个体的模型（individual based model）对这一转型过程展开研究。本模型刻画了农业起源、社会劳动分工与人类行为多样性之间的内在关联。我们设置了两类不同的生境场景：在前新石器时代生境中，资源随时间波动，且无大规模食物储备；在新石器时代生境中，主动的粮食生产会带来经济剩余。我们设定了一个有性繁殖的社会群体，群体中的个体为生存需完成不同任务。我们假设，个体完成任务的效能既存在部分遗传基础，也会随经验积累与学习而提升。由于不同任务所需技能存在差异，我们假定个体在不同任务的遗传倾向性之间存在权衡关系。个体天生携带经遗传获得的任务选择策略，并可通过模仿更为成功的同类来优化自身策略。研究结果表明，在新石器时代场景下，只要稀缺商品的价值更高，表型特化（任务选择策略）与遗传多态性的出现均具备可行性。随着任务数量的增加，特化仅能在规模极大的群体中得以演化。尽管本模型中表型特化往往能够自发形成，但遗传多态性的出现则要求个体在模仿与择偶环节均具备较强的选型匹配性（assortativity）。综上，本模型表明，当经济剩余得以产生时，行为特化与大规模劳动分工大概率会随之出现。因此，本模型有助于阐释新石器时代转型的若干特征，同时也可为当前的遗传多态性研究提供一定启示。