Project Cyclops, A Design... - Department of Earth and Planetary ...

development and remainedlittle changeduntil the
present day:thesearetheso-called "livingfossils."
Gradually, asmulticellular organisms evolved, differentgroupsofcellsbecame
adapted toperformingspecial
functionsthatincreased the survival capability of the
organism. In the animal kingdom, certain of these cells
formed into a nervous system. These communication
links between different parts of the animal enabled a
more coherent behavior in response to environmental
threat. Skeletal structures developed for support, respiratory
systems for increasing the efficiency of gas
exchange, circulatory systems for carrying the gases and
nutrients to the tissues, digestive systems for preprocessing
organic foods, excretory organs for removing the
end products of metabolism, and reproductive systems
for increasing the odds of survival and for ensuring a
constant mixing of genetic material.
In the animal kingdom, a crucial event was the
gradual emergence of animals able to exist on the land.
Successful adaptation to the land demanded not only
alterations in the respiratory apparatus, but also the
development of limbs to permit foraging for food and
escaping from danger. It is generally thought that the
great increase in complexity of the nervous system,
which was necessary in the land animals, was a stimulus
to the further evolution of the central nervous system
essential for the later development of intelligence.
As animals and plants colonized the land, species
diversified into a wide variety of organisms including
birds, flowering plants, amphibians, and giant reptiles,
the dinosaurs. The dinosaurs lacked two critical physiological
systems that were combined in an evolving group
of small animals called mammals. The mammals had
developed a control system for the regulation of internal
temperature and a mechanism for allowing the protection
of the young inside the body of the female
during early development. The conditions responsible
for the extinction of the dinosaurs are not known, but
the mammals survived them. At some point, perhaps a
hundred million years ago, the mammals developed the
capability of living in trees, as their descendants, the
lemurs, marmosets, and monkeys, do today.
Further evolution of the central nervous system
accompanied the arboreal mode of life. Control systems
for vision, orientation, balance, and movement are
necessarily complex, and demanded further sophistication
of the central processing system in the brain.
Twenty million years ago, the brain had enlarged to a
volume of about a hundred cubic centimeters and
contained millions of nerve cells functioning as a highly
integrated control system. It is usually thought that
environmental processes, including competition with
other species, now favored the emergence of small
groups of monkeylike species, increasingly able to
survive in the open grasslands. Many of the adaptations
needed for tree living, such as stereoscopic vision, precise
orientation and balance, and great precision of movement,
paved the way for the evolution of early man on
the plains. (An interesting question about extraterrestrial
biological evolution is whether trees are in fact necessary
for this phase of development of the central nervous
system.)
Existence on the plains favored further anatomical
changes: adoption of the upright posture, and adaptation
of the teeth and the jaws to the new and tough
animal and plant foods. It is generally supposed that the
hands, now freed, became adapted for the precise
manipulation of tools. The thumb, for example, could
be opposed to the fingers for grasping, and was capable
of a much greater range of movement. Along with the
changes in the body came further enlargement of the
brain, principally in the cerebral hemispheres. Success at
hunting in the plains was enhanced by the evolution of
early speech patterns, and further by coordinated
behavior between members of a group.
The fossil record shows that some two million years
ago the brain size had increased, in a species called
Australopithecus, to about 500 cubic centimeters. Australopithecus
lived in the African plains, used tools, and
was carnivorous. Early forms of group behavior and
effective communication between individuals had probably
emerged.
Two events of major significance were occurring as a
result of the progressive enlargement of the brain. The
first was the development in the cerebral hemispheres of
an internal model of the external world and the second
was the ability to pass on these models to the young and
to other adults by communication and reinforcement.
CULTURAL EVOLUTION AND
DEVELOPMENT
OF INTELLIGENCE
In the lower animal species, the brain controls the
behavior of an individual in a fairly stereotyped way.
Reactions to the stresses of the environment are limited
in terms of the options available. The brain acts in
response to a genetically determined and comparatively
simple model of the external world. In early man, the
model was slowly developing into a more complex form.
Association between events could be recognized and
instated in the internal model so that more intelligent
responses to the environment became feasible. An
Australopithecine individual endowed with a cerebral
hemisphere that allowed better association processes
would be more efficient in hunting and, according to the
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