"X-ray vision" and the evolution of forward-facing eyes.

Why do our eyes face forward, and why do many mammals have eyes facing sideways? Here, we describe results suggesting that the degree of binocular convergence is selected to maximize how much the mammal can see in its environment. Mammals in non-cluttered environments can see the most around them with panoramic, laterally directed eyes. Mammals in cluttered environments, however, can see best when their eyes face forward, for binocularity has the power of "seeing through" clutter out in the world. Evidence across mammals closely fits the predictions of this "X-ray" hypothesis.

[1]  Derek H. Arnold,et al.  Staying focused: a functional account of perceptual suppression during binocular rivalry. , 2007, Journal of vision.

[2]  Pascal Mamassian,et al.  Amodal Completion and the Perception of Depth without Binocular Correspondence , 2002, Perception.

[3]  K Nakayama,et al.  Stereoscopic Depth: Its Relation to Image Segmentation, Grouping, and the Recognition of Occluded Objects , 1989, Perception.

[4]  W. E. Le Gros Clark,et al.  History of the primates , 1950 .

[5]  Shinsuke Shimojo,et al.  Interocularly unpaired zones escape local binocular matching , 1994, Vision Research.

[6]  K. Nakayama,et al.  Real world occlusion constraints and binocular rivalry , 1990, Vision Research.

[7]  Christopher P Heesy,et al.  On the relationship between orbit orientation and binocular visual field overlap in mammals. , 2004, The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology.

[8]  Carol R. Ember,et al.  Research frontiers in anthropology , 1994 .

[9]  J. Sprague,et al.  Progress in physiological psychology , 1966 .

[10]  John D. Pettigrew,et al.  Comparison of the Retinotopic Organization of the Visual Wulst in Nocturnal and Diurnal Raptors, with a Note on the Evolution of Frontal Vision , 1978 .

[11]  Jason M. Holmes.  The Illustrated Encyclopedia of Trees , 2003 .

[12]  B. Grzimek,et al.  Grzimek's Animal Life Encyclopedia , 1984 .

[13]  R. Tuttle,et al.  The Functional and evolutionary biology of primates , 1973 .

[14]  Shinsuke Shimojo,et al.  An occlusion-related mechanism of depth perception based on motion and interocular sequence , 1988, Nature.

[15]  M. Cartmill.  Arboreal Adaptations and the Origin of the Order Primates , 1972 .

[16]  Peter Lennie,et al.  Binocular integration of partially occluded surfaces , 2002, Vision Research.

[17]  K. Nakayama,et al.  Amodal Representation of Occluded Surfaces: Role of Invisible Stimuli in Apparent Motion Correspondence , 1990, Perception.

[18]  D. Rasmussen.  Primate origins: Lessons from a neotropical marsupial , 1990, American journal of primatology.

[19]  D. Maddison,et al.  The Tree of Life Web Project , 2007 .

[20]  Robert W. Sussman,et al.  Primate origins and the evolution of angiosperms , 1991, American journal of primatology.

[21]  E. Hill.  Journal of Theoretical Biology , 1961, Nature.

[22]  David More,et al.  The Illustrated Encyclopedia of Trees , 2002 .

[23]  Shinsuke Shimojo,et al.  Da vinci stereopsis: Depth and subjective occluding contours from unpaired image points , 1990, Vision Research.

[24]  Marc Bekoff,et al.  Encyclopedia of Animal Behavior , 2004 .