Doctoral Dissertation Research: A test of the vocal grooming hypothesis in the gelada

关于人类语言起源的一个耐人寻味的假说是，它作为一种“社交工具”出现，促进了我们与越来越多的人保持关系的能力(“社交修养假说”)。基本的想法是，社交礼仪(只促进与一个人的联系)被声音“礼仪”(同时促进与几个人的联系)所取代。事实上，社会纽带对人类和非人类灵长类动物都有适应价值。因此，如果声音接触是维持关系的一种有效方式，那么选择应该有利于它的发展。然而，尽管有大量的理论支持，社交修养假说还有待于实证检验。狐狸提供了一个很好的模型来测试这一点，因为它们高度社会化，非常善于发声，而且独特的时间限制，因为它们一天中的大部分时间都必须花在草丛中。这项由密歇根大学博士生伊丽莎白·约翰逊(Elizabeth Johnson)在杰辛塔·贝纳博士的指导下进行的研究，将探索雌性狐狸维持社交网络的策略，重点是何时使用发声，它们引起的反应，以及当时间预算特别紧张时，这种发声接触是否补充或取代社交修饰。通过综合运用行为观察、社会网络分析、“压力”荷尔蒙分析和发声录音声学分析等方法，这项研究将阐明人类祖先维持社会纽带的一种可能途径，从而形成更大的群体和更大的群体凝聚力。这项研究的结果不仅有助于更好地了解雌性狐猴的社会关系，而且还为正在进行的关于近亲物种(例如阿努比斯和哈马德里亚狒狒)的合作项目提供了一个比较数据集。此外，这项研究超越了学术界，提高了人们对研究地点(濒危世界遗产埃塞俄比亚西米恩山国家公园)和研究物种的认识，这是埃塞俄比亚高原的特有物种，被世界自然保护联盟红色名录列为“受威胁”保护状态。最后，这一博士论文研究项目通过雇用当地一名现场助理(为这些年轻人提供就业机会和继续教育)，与公园官员密切合作，并向埃塞俄比亚国民提供教育讲座，为公园的长期生存做出了贡献。

One intriguing hypothesis about the origins of human language is that it emerged as a 'social tool,' facilitating our abilities to maintain relationships with an increasing number of people (the "social grooming hypothesis"). The basic idea is that social grooming (which facilitates a bond with only one individual) is replaced by vocal 'grooming' (which facilitates bonds with several individuals, simultaneously). Indeed, social bonds have adaptive value for both humans and non-human primates. Thus, if vocal contact represents an efficient way to maintain relationships, then selection should favor its development. Despite a great deal of theoretical support, however, the social grooming hypothesis has yet to be tested empirically. Geladas provide an excellent model to test this because they are highly social, exceptionally vocal, and uniquely time-constrained because they must spend much of their day foraging on grass. This research by doctoral student Elizabeth Johnson (University of Michigan), under the supervision of Dr. Jacinta Beehner, will explore the strategies that female geladas employ to maintain their social networks, with a specific emphasis on when vocalizations are used, the responses they elicit, and whether such vocal contact supplements or replaces social grooming when time budgets are particularly strained. By utilizing a combination of methods, including behavioral observation, social network analysis, analysis of 'stress' hormones, and acoustic analysis of recorded vocalization, this research will elucidate one possible route by which human ancestors may have maintained social bonds, allowing for larger groups and greater group cohesion. Results from this study not only contribute to a better understanding of female gelada social relationships, but also provide a comparative dataset for on-going collaborative projects on closely related species (e.g., anubis and hamadryas baboons). Further, this research extends beyond academia, raising awareness about the study site (the Simien Mountains National Park of Ethiopia, a World Heritage Site in Danger) and the study species, an endemic species to the highlands of Ethiopia with a conservation status labeled as "Threatened" by the IUCN Red List. Finally, this doctoral dissertation research project contributes to the long-term viability of the park by hiring a local field assistant (providing both employment opportunities as well as continuing education for these young adults), working closely with park officials, and providing educational lectures to Ethiopian nationals.