"If we knew what it was we were doing, it would not be called research, would it?" - Albert Einstein


EVOLUTION OF THE PRIMATE VISUAL SYSTEM
Activity Pattern
My research has concentrated on the evolution of the primate visual system.  In collaboration with Callum Ross (now at U. of Chicago), I have studied the correlated evolution of orbit morphology and color vision with activity pattern by including data from both extant and fossil primates. Our analyses support the hypothesis that a nocturnal activity pattern is primitive for primates.
Relevant Publications:
 Heesy & Ross (2001) Evolution of activity pattern and chromatic vision in primates: morphometrics, genetics and cladistics. Journal of Human Evolution 40: 111-149.
 Heesy & Ross (2004) Mosaic evolution of activity pattern, diet, and color vision in haplorhine primates. From Anthropoid Origins: New Visions, edited by Callum Ross and Rich Kay.
 Ross, Hall & Heesy (2007) Were basal primates nocturnal? Evidence of eye and orbit shape. In Primate Origins: Adaptations and Evolution, edited by Matt Ravosa and Marian Dagosto.
 

Orbit Orientation
I have also studied the evolution of orbit orientation in primates as compared to other mammals. One study demonstrated that visual field shape, especially binocular visual field overlap, is a function of orbit orientation in mammals. The overall purpose of this research was to re-evaluate the Cartmill-Allman-Pettigrew Nocturnal Visual Predation Hypothesis for the origin and evolution of the primate visual system.  Multivariate analyses of a large mammalian orbit orientation dataset demonstrated that convergence is most highly correlated with activity pattern and diet. Nocturnal and faunivorous non-primate eutherians have the highest mean orbit convergence, and are most similar to primates in this morphology. 

Relevant Publications:
 Heesy (2004) On the relationship between orbit orientation and binocular visual field overlap in mammals. The Anatomical Record 281A: 1104-1110.
 Heesy (2008) Ecomorphology of orbit orientation and the adaptive significance of binocular vision in primates and other mammals. Brain, Behavior and Evolution 71: 54-67. 
 Heesy (2009) Seeing in stereo: The ecology and evolution of primate binocular vision and stereopsis. Evolutionary Anthropology 18: 21-35. 

Orbit Morphology and Oculomotor Function
Hypotheses regarding the functions of the primate postorbital bar and haplorhine postorbital septum have played prominent roles in studies of the primate visual system. Studies conducted with Callum Ross and Brigitte Demes (Stony Brook) on the morphology of the mammalian lateral orbit as well as analyses of ocular kinematic data support previous hypotheses that the postorbital bar and septum function to insulate the eye and orbital contents from disruptive contractions of the masticatory apparatus.
Relevant Publications:
 Heesy (2005) Function of the mammalian postorbital bar. Journal of Morphology 264: 363-380.
 Heesy, Ross, & Demes (2007) Oculomotor stability and the functions of the postorbital bar and septum. From Primate Origins: Adaptations and Evolution, edited by Ravosa and Dagosto. 

EVOLUTION OF THE AVIAN VISUAL SYSTEM
Orbit Orientation, Binocular Vision and Wulst Evolution
A collaborative project conducted with Andrew Iwaniuk (U. of Lethbridge), Meg Hall (Midwestern U.), and Doug Wylie (Alberta) demonstrated that orbit orientation, binocular overlap and Wulst volume are correlated - taxa with higher orbit convergence and binocular overlap have relatively larger Wulst volumes.
Relevant Publications:
 Iwaniuk, Heesy, Hall & Wiley (2008) Relative Wulst volume is correlated with orbit orientation and binocular visual field in birds. Journal of Comparative Physiology A.


CLADISTIC RECONSTRUCTION OF PRIMATE BIOGEOGRAPHY
I have also been involved in exploring the efficacy of cladistic methods of character reconstruction for the biogeographic origins of primate higher taxa in collaboration with Nancy Stevens and Karen Samonds.
Relevant Publications:
 Heesy, Stevens, & Samonds (2006) Biogeographic origins of primate higher taxa. From Current Issues in Primate Biogepgraphy, edited by Fleagle and Lehman.
 Stevens & Heesy (2006) Malagasy primate origins: Phylogenies, fossils, and biogeographic reconstructions. Folia Primatologica 77: 419-433.