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There are over 1.3 million named and catalogued species on earth, and
scientists estimate there are over 7 million more unnamed, unknown and
undiscovered creatures sharing the planet with us.
What is it about humans that makes us distinct?
Modern human behavior arguably emerged between 300 and 30 thousand years ago,
when our ancestor's brains began to structurally and functionally
resemble our own.
It was then that humans began to think symbolically.
Symbolic thought gave rise to language, art, music, religion,
philosophy, science and complex technologies that allowed us to
circumvent evolutionary and environment constraints.
Our brains are the key to our evolutionary success.
Weighing in at only about three pounds fully grown, our brain stores our
every memory, generates every thought and feeling, and allows us to touch,
see, and interact with our world.
Our brains are among the largest in the animal kingdom, but elephants,
whales and dolphins have even bigger brains.
So clearly size isn't everything.
The key to the human brain's unique capacities is not its size, but its
inner wiring.
Protected by the skull, the brain is part of one of two great divisions of
our nervous system, which work together to allow us to sense and
react to our world.
The brain and spinal cord form the first great division, our central
nervous system (or CNS).
The second great division is the peripheral nervous system (or PNS).
The brain sends messages via the spinal cord to the peripheral nerves
throughout the body that control our skeletal muscles in our arms and legs,
and internal organs.
Messages are carried throughout central and peripheral nervous system
by specialized cells.
Cells are the smallest structural and functional unit of a living organism,
and the human body contains over 300 different types with highly
specialized functions.
Cells that can receive, process and transmit electrical impulses in our
nervous system are called neurons.
Staggeringly complex, the brain is made up of some 100 billion neurons,
plus a myriad of other cell types.
Networks of neurons exchange information among dozens of brain
areas specialized for different tasks, and researchers suspect that it is
something about the organization and function of these networks that may
hold the key to our uniquely human brain.