Biology Reference
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ticos; they represented healing to the ancient Greeks, and for that reason a pair of en-
twined snakes still symbolizes medicine. Today Hindus, Hopis, and Appalachian Pente-
costals incorporate venomous species in sacred rituals, and rural people zealously pro-
tect Madagascan ground boas, Texas indigos, and other snakes that eat species we re-
gard as pests.
Beyond emotional satisfaction and symbolism, we have also long used serpents
for material benefits. Prehistoric kitchen middens contained eastern diamond-backed
rattlesnake bones, and modern subsistence hunters eat African pythons. 4 Entire dis-
tricts of Asian cities are devoted to processing reptiles for food, snakeskin products sell
for hundreds of millions of dollars annually, and the pet trade has reached mind-bog-
gling levels—in one recent year two hundred million dollars' worth of snakes and snake
products was imported into the United States alone. And despite claims of promoting
safety and research, rattlesnake roundups are fueled by economics, bringing hundreds
of thousands of dollars to small Oklahoma and Texas towns in a weekend.
All that individual and cultural complexity raises some obvious questions: Does our
ambivalence reflect scriptural linkage with the fall of man? Could skin-shedding signi-
fy renewal? And if our attitudes toward serpents reflect something more primal, like
predation, why are we fearful of and drawn to them? In an earlier topic, I noted that
snakes kill and are killed by tarsiers, monkeys, and apes, which implies that they have
inspired terror as well as curiosity since the very dawn of primate ancestry. From our
earliest ponderings, I reasoned, snakes have loomed as horrifying yet edible, paradoxic-
ally repulsive and at the same time valuable. Animal behaviorist Lynne Isbell has since
advanced that perspective with a more comprehensive theory. Ancestral primates faced
constrictors that could eat them, she points out in TheFruit,theTree,andtheSerpent,
and by the time apes diverged from monkeys, venomous species also had appeared. 5
This chronology corresponds with major events in brain and vision evolution, and as we
shall see, new evidence supports her hypothesis that fear of being squeezed predates
our dread of toxic bites.
As background, serpents originated at least one hundred million, and maybe as much
as a hundred and forty million years ago. 6 Among salient features, elongation—allowing
them to enter places unsuitable for thicker bodies—limb reduction, and a forked tongue
accompanied the group's debut, and they share with lizards the distinction of having
paired penises. Snakes are unusually successful, with about 3,400 living species—more
than twice as many as geckos or skinks. Although modern pythons swallow calves and
other notoriously large meals, the earliest serpents likely ate animals without back-
bones, while their crafty ways and chemical worldviews served to explore new habitats
and avoid enemies. Those first snakes were irrelevant to us, millions of years too early
and too small to be dangerous anyway, although adaptations for eating bulky items were
surely in place before primates came on the scene. Through it all, snakes have lain low
and been hard to see. And as we'll discuss in the next chapter, venoms are a more re-
cent, profoundly important addition to that lifestyle.
On our side of the adversarial relationship, primates guide grasping hands and feet
with big brains and binocular vision, unlike rodents, who steer paws by olfaction. Our
particular branch of the mammalian evolutionary tree began almost eighty million years
ago, before the decline of large dinosaurs at the end of the Mesozoic. Flowering plants
and insects flourished as we diverged from a common ancestor with flying lemurs, our
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