Brain evolution in the context of efficient resource extraction

大脑大小的增加是人类进化史的一个重要特征。因为脑组织在代谢上是昂贵的，所以关于人类起源的一个中心问题是，我们的祖先是如何获得生长和维持大型大脑所需的额外能量的。目前的假说集中在相对较新的行为变化上，表明吃肉、食品加工或烹饪可能提高了饮食质量，并导致了更高的净能量收益。然而，大脑的扩张并不局限于人类的血统；它是灵长类动物中一种更古老、更普遍的模式。这表明，一个更基本的过程是导致这种耗费能量的大脑扩张的早期阶段的原因。最近有一种说法认为，灵长类拥有一种复杂的“心智工具包”，使它们能够比其他物种更有效地从栖息地获取资源。然而，我们不可能充分评估这一假说，因为我们缺乏关键的比较生态学数据。这项研究的目的是测试灵长类动物是否比其他吃水果的物种更聪明或更好地觅食，这两种物种都得益于它们更大的大脑，并为它们提供了能量支持。六种食果性哺乳动物的活动将使用GPS跟踪记录，在一年中一个生态上简单的时间段，当这些物种共享一个单一的主要水果来源(Dipteryx Oleifera)时。通过比较生活在同一栖息地的远亲但生态相似的物种寻找食物的方式，该项目将测试1)运动和食物开发模式是否与动物对其栖息地了解的物种水平的差异一致，以及2)复杂的觅食策略是否会导致更有效的资源获取。如果这些都得到支持，这项研究将提供证据支持灵长类认知进化的“正反馈循环模型”：大脑体积的增加(来自社会和/或生态压力)会导致认知能力的增强，从而提高食物采集的效率，而这反过来又会产生能量过剩，从而促进更大的大脑的生长。如果不同物种的认知能力和觅食成功没有差异，那么这些结果将挑战关于灵长类觅食行为相对复杂的普遍假设，并迫使人们重新审视灵长类大脑扩张的早期阶段是如何获得能量资助的。为了扩大这些结果的影响，研究人员将制作在线视频，讲述这项研究如何有助于我们理解人脑的进化。此外，还将通过与北卡罗来纳州自然科学博物馆的合作，向博物馆参观者介绍实地网络直播的最新情况，促进对科学和研究进程的了解。外联活动还将包括为巴拿马学童创造机会参加培训研讨会，获得科学研究的实践经验，并与巴拿马和美国的科学家见面和互动，促进科学教育和欣赏。最后，该项目将通过培训美国和巴拿马的本科生来加强对未来科学家的教育，这些本科生的背景在生物人类学领域传统上没有得到充分的代表。

The increasing of brain size is a defining feature of human evolutionary history. Because brain tissue is metabolically expensive, a central question about human origins is how our ancestors acquired the additional energy necessary to grow and maintain large brains. Current hypotheses focus on relatively recent behavioral changes, suggesting that meat-eating, food processing, or cooking may have increased diet quality and led to higher net energy gain. Brain expansion, however, is not restricted to the human lineage; it is an older and more general pattern across the primates. This suggests that a more fundamental process is responsible for the early stages of this energetically expensive brain expansion. One recent suggestion is that primates possess a sophisticated 'mental tool-kit' that enables them to extract resources from their habitat more efficiently than other species. It has been impossible to adequately evaluate this hypothesis, however, because we lack the critical comparative ecological data. The aim of this research is to test if primates forage 'smarter' or 'better' than other fruit-eating species, both facilitated by, and energetically supporting, their larger brains. The movements of six frugivorous mammals will be recorded using GPS tracking during an ecologically 'simple' time of year when a single, major fruit source (Dipteryx oleifera) is available that is shared by these species. By comparing how distantly related, but ecologically similar, species living in the same habitat find food, this project will test if 1) patterns of movement and food exploitation are consistent with species-level differences in what animals know about their habitat, and 2) if complex foraging strategies lead to more efficient resource acquisition. If these are supported, the research will provide evidence to support a 'positive feedback loop model' for primate cognitive evolution: Increased brain-size (arising from social and/or ecological pressures) leads to enhanced cognitive abilities that improve food-gathering efficiency, while this, in turn, generates an energetic surplus that potentiates the growth of a bigger brain. If cognitive abilities and foraging success do not differ among species, then alternatively, these results will challenge widespread assumptions about the relative sophistication of primate foraging behavior, and force a reexamination of how the early stages of primate brain expansion were energetically financed. To broaden the impact of these results, researchers will create online videos about how this study contributes to our understanding of evolution of the human brain. In addition, live web-cast updates from the field will be presented to museum visitors through collaboration with the North Carolina Museum of Natural Sciences, fostering understanding of science and the research process. Outreach activities also will include creation of opportunities for Panamanian school children to attend training seminars, gain hands-on experience with scientific research, and meet and interact with both Panamanian and US scientists, fostering science education and appreciation. Finally, the project will enhance education of future scientists through training of both US and Panamanian undergraduate students from backgrounds that have traditionally been underrepresented in the field of biological anthropology.