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.
