The evolution of intelligence among early large
mammals of the grasslands was due in great measure to
the interaction between two ecologically synchronized
groups of these animals, the hunting carnivores and the
Line 5 herbivores that they hunted. The interaction resulting
from the differences between predator and prey led to a
general improvement in brain functions; however, certain
components of intelligence were improved far more than
others.
Line 10 The kind of intelligence favored by the interplay of
increasingly smarter catchers and increasingly keener
escapers is defined by attention—that aspect of mind
carrying consciousness forward from one moment to the
next. It ranges from a passive, free-floating awareness to
Line 15 a highly focused, active fixation. The range through these
states is mediated by the arousal system, a network of
tracts converging from sensory systems to integrating
centers in the brain stem. From the more relaxed to the
more vigorous levels, sensitivity to novelty is increased.
Line 20 The organism is more awake, more vigilant; this
increased vigilance results in the apprehension of ever
more subtle signals as the organism becomes more
sensitive to its surroundings. The processes of arousal and
concentration give attention its direction. Arousal is at
Line 25 first general, with a flooding of impulses in the brain stem;
then gradually the activation is channeled. Thus begins
concentration, the holding of consistent images. One
meaning of intelligence is the way in which these images
and other alertly searched information are used in the
Line 30 context of previous experience. Consciousness links past
attention to the present and permits the integration of
details with perceived ends and purposes.
The elements of intelligence and consciousness come
together marvelously to produce different styles in
Line 35 predator and prey. Herbivores and carnivores develop
different kinds of attention related to escaping or chasing.
Although in both kinds of animal, arousal stimulates the
production of adrenaline and norepinephrine by the
adrenal glands, the effect in herbivores is primarily fear,
Line 40 whereas in carnivores the effect is primarily aggression.
For both, arousal attunes the animal to what is ahead.
Perhaps it does not experience forethought as we know it,
but the animal does experience something like it. The
predator is searchingly aggressive, inner-directed, tuned
Line 45 by the nervous system and the adrenal hormones, but
aware in a sense closer to human consciousness than, say,
a hungry lizard's instinctive snap at a passing beetle.
Using past events as a framework, the large mammal
predator is working out a relationship between
Line 50 movement and food, sensitive to possibilities in cold
trails and distant sounds—and yesterday's unforgotten
lessons. The herbivore prey is of a different mind. Its
mood of wariness rather than searching and its attitude
of general expectancy instead of anticipating are
Line55 silk-thin veils of tranquility over an explosive endocrine
system.