topics: |  brain | neuro-science | evolution | psychology | illusion

The story is extensively simplified and downright incorrect in places, but
the telling, and the excellent b&w illustrations, spin a vivid tale.  Jastrow
was a geophysicist who foounded NASA's Goddard Institute.

1. Across the Threshold of Life
2. The Beginnings of Intelligence
3. Thinking in the Dark: The Smell Brain
4. Into the Light: The Vision Brain
5. Brains and Computers
6. Circuits in the Brain
7. A Guiding Hand
8. The Final Step
9. The Old Brain and the New
10. Our Brain's Successor
11. The Thinking Computer
12. An End and a Beginning

Excerpts

[3,4 billion years ago - Life appears]

    Nature's experiments on the origin of life seem to have come to fruition
in a rather short time. This fact suggests that the experiments may have been
easy, and the chances of success fairly high. According to the fossile
record, relatively complicated organisms like bacteria already existed when
the earth was only one billion years old.  Although a bacterium seems like a
simple kind of life to us, it is a quite complex chemical factory, whose
existence depends on the simultaneous manufacture of several thousand
different kinds of chemicals. Bacteria are far more advanced than those
simple creatures that first wriggled across the threshold of life on the
earth.

    If bacteria already existed when the earth was one billion years old, a
long period of evolution must have preceded their appearance, in which the
chemical machinery that makes up the business of life for a bacterium was
slowly being worked out and improved..  This implies that the threshold of
life itself must have been crossed far earlier - perhaps when the earth was
only a few hundred million years old, or even younger. A few hundred million
years is not a long time for such an important experiment; if the experiment
succeeded as quickly as that, the probability of its success must have been
fairly high..

    In the next half billion years or so, very little happeed; at least,
little that is preserved in the fossil record. p.22-23

450 million years ago - the first Fishes

    The first fishes possesed a first-class skeleton with bones in fin as
well as spine. They also posessed a brain. It was a very small brain, but it
was the first one that had existed on the earth up to that time. p.24

[300 million years ago - the first Reptiles]
    The fish's brains is divided cleanly into three
compartments: a front compartment for smell, a middle compartment for vision,
and a rear compartment for balance and coordination. p.24 [ reptile forebears
were similar. fig. 128]

    These arrangements were inherited from the simple brain of the
fishes. The receptors for vision and smell were coordinated in a region
between the smell brain and vision brain, which was a command post called the
diencephalon. Here, the inputs from different senses were compared and put
together for a program of action. p. 128

    The basic instincts of survival - sexual desire, the search for food and
the aggression responses of "fight-or-flight" - were wired into this region
of the reptile's brain. 129

200 million years ago - the first Mammals

    When the mammals evolved out of the reptiles, their brains began to
change. First they developed a new package of instincts, related to the
reptilian instincts for sex and procreation, but modified for the special
needs of a mammalian lifestyle. Chief among these was the instincts for
parental care of the young. Here was a revolutionary advance over the
behavior of reptile parents, for whom the newly hatched young provided a
tasty snack if they could catch them. But the reptile young were prepared to
fight for their lives. In the population of the mammals, on the other hand,
the young arrived in a helpless and vulnerable state, and parental affection
was essential for their survival.

    The new instincts of the mammals for parental care did not replace the
older reptilian instincts; they augmented them. The ancient programs of the
reptile brain - the search for food, the pursuit of a mate, and flight from
the predator - were still essential to survival. As a result, the command
post in the brain that controlled instintive behavior grew larger.

    The brains of the mammals changed in another important way, that was
related to their nocturnal lifestyle. As these animals passed into their
100-million-year time of darkness, the vision brain diminished in importance
and the smell brain expanded.

    The two swellings in the smell brain were the cerebral hemispheres. In
the beginning, when the smell was the main function of the cerebral
hemispheres, these parts of the brain were modest in size and could be fitted
into the cranium of the mammal without wrinkling or folding. Later, when the
ruling reptiles disappeared and the mammals began to move about by day and
rely on the sense of vision as well as smell, more circuits had to be added
to the brain to receive the new information from the eyes and analyze it. The
added circuits for vision were in the cerebral hemispheres, which swelled to
an even larger size as a result.

120 thousand years ago - Homo Sapiens appears

The growth of the cerebral cortex accelerated further in man´s immediate
ancestors, and reached explosive proportions in the last million years of
human history, culminating in the appearance of Homo Sapiens.

The primitive region in the brain, that held the circuits for the
instinctive behavior of the reptile and the old mammal, was now completely
enveloped by and buried within the human cerebral cortex.

Yet this ancient command post, relic of our distant past, is still active
within us; it still vies with the cerebral cortex for control of the body,
pitting the inherited programs of the old brain against the flexible
responses of the new one.

Experiments suggest that parental feelings, source of some of the finest
human emotion, still spring from these primitive, programmed areas of the
brain that go back to the time of the old mammal, more than 100 million years
ago.

One part of the old brain, called the hypothalamus, is only the size of a
walnut in the human brain, and yet a minute electrical stimulus applied to
this region in the brain can create the emotional states of anger, anxiety or
acute fear. The stimulation of nearby regions, only a few tenths of an inch
away, produces sexual desire, or a craving for food or water.

The hypothalamus also appears to contain centers for aggression, killing,
and fight-or-flight responses.

Experiments indicate that states of anger and aggression are created by
electrical signals originating in the hypothalamus. The hypothalamus behaves
as though it contains a gate that can open to let out a display of anger or
bad temper.

Normally, this gate is kept closed, but now and then the animal´s senses
tell its brain that its rights are endangered; a mate is lured away, food is
stolen, or threat signals are received; and then the package of brain
survival programs called the "emotions" comes into play, and an electrical
signal to open the gate comes from som ancient center of instinct deep within
the brain.

It is as if two mentalities resided in the same body. One mentality is
ruled by emotional states that have evolved as a part of age-old programs for
survival. The other mentality is ruled by reason, and resides in the cerebral
cortex.

In man, the cerebral cortex, or new brain, is usually master over the old
brain. But the reptile and the old mammal still lie within us.

These properties of the human brain lead to a prediction regarding the
life that will follow man. As nature built the new brain on top of the old in
our ancestors, so too, in the next stage of evolution after man, we can
expect that a still newer and greater brain will join the "old" cerebral
cortex, to work in concert with the cerebral cortex in directing the behavior
of a form of life as superior to man as he is to the ancient forest mammal.

The book has quite a few errors, and is rather opinionated.  E.g. here's a
challenge to the the E = mc² law (p. 81):
   Each computing cell combines the signals from several hundred separate
   cells in the retina and forms a small, circular patch of light out of
   them.
The large number of photons being transformed, it is claimed, should result
in all of us exploding.  I am not sure where this comes from. - AM

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