Oxyopia Abstract

March 9, 2007
Friday, 4:00 PM
489 Minor Hall

Lynne Isbell, PhD
Professor, Department of Anthropology, University of California, Davis
Host: Dennis Levi

Title

Eve's Legacy: Snakes and the Origins of Primates

Abstract

A gradient in brain size exists in mammals, with humans having much larger brains than those of the great apes, who themselves have larger brains than other primates. Primates as a whole have larger brains than other mammals. About half of the neocortex in primates is involved with vision, and indeed, their heavy reliance on vision is what sets primates apart from other mammals. Thus, whatever it was that led to our own huge brains started with the first primates. In this talk, I will describe a new theory for the origin of those first primates and their special brains. The Snake Detection theory proposes that (1) the appearance of snakes may have initially led to the expansion of mammalian visual systems, (2) the appearance of constricting snakes about 100 million years ago may have led to the origin of primates via expansion of the mammalian visual systems, and (3) the appearance of venomous snakes about 60 million years ago may have led to the origin of anthropoid primates and further expansion of the primate visual systems. I also explain why other mammals did not respond similarly to venomous snakes and why the visual systems of Old World fruit bats are convergent with those of primates. I discuss the myriad levels of evidence in support of this theory, including biogeography, primate ecology, neurophysiology, and brain anatomy. The echos of visual and behavioral adaptations to snakes are still present in our brains today, including our fear of snakes and our remarkable pre-conscious "blindsight" early warning system.

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