The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

A comparative analysis of hippocampus size and ecological factors in primates


1School of Biomedical Sciences, Kent State University, 2Department of Anthropology, The George Washington University, 3Department of African Zoology, Royal Museum for Central Africa, 4Laboratory of Histology and Neuropathology, Université Libre de Bruxelles, 5Department of Anthropology, University of Arkansas, Fayetteville

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Primates vary in their need to store spatial and temporal information for foraging and distinguishing food quality. The hippocampus plays a role in spatial navigation and episodic memory. This study investigates the effect of environmental factors, such as diet, home range size, activity pattern and habitat, on variation in hippocampal volume among primates. We hypothesized that primates with highly frugivorous diets and larger home ranges would have relatively larger hippocampal volume compared to folivorous/insectivorous primates and primates with smaller home ranges. Furthermore, we expected that arboreal primates would have larger hippocampal volumes than terrestrial primates, resulting from an increased reliance navigating in the complex three-dimensional space of the canopy. We did not expect hippocampal volume to differ between nocturnal and diurnal primates. Using uncorrected and phylogenetic independent contrast analyses on 42 primate species, body size-adjusted hippocampal volume was significantly increased in primates with a frugivorous diet. Conversely, primarily insectivorous primates demonstrated a negative correlation with hippocampal size, suggesting they have smaller hippocampal volumes. As predicted, hippocampal volume increased in association with home range size and activity patterns had no effect on primate hippocampal volume. Surprisingly, arboreal primates did not differ from terrestrial primates in hippocampus size. These results demonstrate that environmental factors related to diet and home range size may selectively shape an increase or decrease in hippocampal volume in primates due, in part, to its role in spatial memory. This study also adds to a growing body of research in support of the mosaic theory of cognitive evolution.

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