Biology Reference
In-Depth Information
joint pedigree already having split from tree-shrews—themselves squirrel-like creatures
with flexible limbs and somewhat forward-facing eyes. From those earliest primates,
one basal lineage led to Madagascan lemurs, African galagos and pottos, and Asian lor-
ises; Asian tarsiers are closer to the other main lineage, comprising three groups of an-
thropoids. New World monkeys and marmosets are climbers, often with prehensile tails,
whereas Old World monkeys and baboons are frequently terrestrial. The third group of
anthropoids, called hominoids, is more closely related to that last one and includes gib-
bons, orangutans, gorillas, chimpanzees, bonobos, and humans.
Together these narratives confirm that snakes had been around at least twenty milli-
on years when the first, lemurlike primates appeared. By then, as the Mesozoic ended,
a prospering lineage of macrostomatan (“big-mouthed”) serpents, related to boas and
pythons, had combined fine-tuned ambush skills, constricting behavior, and expansive
swallowing abilities. The cards were stacked in their favor when it came to eating mam-
mals, but then again ancestral primates were sharp-eyed, agile-handed, crafty—and get-
ting more so by leaps and bounds, looking to make whatever they could of snakes and
yet ever more terrified of them. We'd embarked upon an evolutionary arms race that
continues to the present, fraught with age-old ambiguities.
Given that nod to deep history, attitudes toward snakes are complexly determined.
Decades of experiments and field observations document that whereas some individual
primates react to serpents with terror, others are just as resolutely curious or indiffer-
ent. Ophidiophobia is indeed easier to induce and harder to extinguish than an aversion
to guns, and naive children pick out hidden snakes in photo arrays, suggestive of an-
case experience also shapes phobias. On balance, our australopithecine ancestors must
have been attuned to natural history, their ophidiophobia and ophidiophilia reflecting a
mélange of innate tendencies, personal travails, and group-held traditions. By the time
those bipedal apes began roaming Pliocene African savannas, roughly four million years
ago, interest in and dread of snakes were already acute, preceding the use of fire, art,
and language.
Lynne Isbell's theory is supported by research showing that we recognize and attend
to danger with a cluster of sequentially evolved brain innovations. As she emphasized,
snakes originated prior to raptors and carnivores, so constrictors may have facilitated
the origin of a uniquely mammalian fear module—a small, deep-seated region between
the temples that is controlled by the amygdala and sends more links to cognitive centers
than vice versa. It's no coincidence when terror trumps reason! Moreover, primate brain
areas specialized for vigilance and alarm connect with neural networks sensitive to the
elongate shapes and partially hidden, repetitive geometric patterns typical of snakes.
However much our feelings derive from culture and experience, Lynne concludes, we
preconsciously evaluate serpentine features thanks to some truly ancient circuitry. With
all that anatomical baggage in mind, this and the next chapter summarize the biology
of my favorite animals, in hopes of enhancing appreciation for their many admirable at-
tributes.
Snakes, as pop novelist Tom Robbins wrote in
Still Life with Woodpecker,
are “all belt
