Page 148 - Darwin's Dilemma: The Soul

Darwin’s Dilemma: The Soul

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a gap around one millionth of a centimeter wide. Therefore, ax-
ons and dendrites do not touch one another directly.
Connections take place in less than one thousandth of a second.
Some neurons sprout as just a few dendrites; others have a very
large number. Were we to try to count the number of connections
arising inside the brain, at a rate of one every second, it would take
3 million years, or 42,000 human generations. 90
In her book An Alchemy of Mind, The New Yorker magazine
writer Diane Ackerman, of Cornell University, provides numerical
details about this complex system:

Impossible as it sounds, we have more brain cell connections than
there are stars in the universe. The visible universe, I mean, since 96
percent of the measurable universe is invisible, to us at least. Linger
with that thought a moment, picturing the infinities of space—a car-
bon-paper night struck through with countless stars. Then picture
the microscopic hubbub in one brain. A typical brain contains about
100 billion neurons, consumes a quarter of the body’s oxygen, and
spends most of the body’s calories, though it only weighs about
three pounds. A ten-watt lightbulb uses the same amount of electri-
cal energy. In a dot of brain no larger than a single grain of sand,
100,000 neurons go about their work at a billion synapses. In the ce-
rebral cortex alone, 30 billion neurons meet at 60 trillion synapses a
billionth of an inch wide. 91
In the words of Nobel Prize winner Gerald M. Edelman, di-
rector of the Neurosciences Institute at the Rockefeller University:
If we counted one synapse per second, we would not finish counting
for 32 million years. If we considered the number of possible neural
circuits, we would be dealing with hyperastronomical numbers: 10
followed by at least a million zeros. 92
One of the most astonishing facts is that any given human
brain, with these extraordinary statistics, is never identical to
any other brain. Brains are not the same even in identical

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