07.+What+is+Intelligence+(February+2006) - Get a Free Blog

What is Intelligence? 128
Evolution is built on two cornerstones: heritable variation and
selection. Plainly, humans vary. The source of that variation is
genetic mutation, which still occurs at around the same rate today as
it has throughout our evolution.
But what about selection? In the west we certainly seem to have
wriggled free of natural selection. It is no longer just the fittest who
survive and reproduce. Modern medicine allows people to overcome
diseases and injuries that would once have killed them. Birth control
and reproductive technology make reproduction a matter of choice,
not adaptive quality. Likewise, the power of sexual selection has
been blunted because the mass media has a strong influence on who
we find attractive, and because "beautiful" people do not necessarily
have the most children.
But that still leaves artificial selection, the force more usually
associated with the domestication of animals and plants. Obviously,
we do not systematically direct the evolution of our own genome in
the way our ancestors did to produce high-yield wheat or miniature
poodles, but there is a parallel: many human traits only exist because
they have been selected for artificially. The invention of spectacles
has allowed myopia to proliferate, dairy farming has given many
adults the ability to digest milk sugar, and stone tools allowed our
earliest ancestors to extend their physical abilities without evolving
bigger muscles. These and countless other innovations have affected
our gene pool.
Other forces are at work, too. Humans are changing the environment,
altering the climate, filling the world with pollution and creating the
conditions for new diseases to emerge - changes that are almost
certainly driving human evolution.
And while we may think that genetic technology will give us control
over our future, it may actually send human evolution in unexpected
directions. It is hubris to think that we can engineer our genome to a
particular end. We know so little about how our genes interact that
any attempts at engineering sperm or eggs may well have
unpredictable results. All we can say for sure is that our gene pool is
changing, perhaps faster than ever. But where evolution will take us
remains a mystery.
Kate Douglas
4 Why do we sleep?
THE average person spends a third of their life asleep, and going
without it kills you quicker than starvation. Sleep seems to be
fundamental in biology: all animals do it, and even cultured neurons
in a Petri dish spontaneously enter a sleep-like state. Yet we don't
know what sleep is for.
There are several ideas, of course, ranging from obvious ones about
restoration and recovery to more elaborate theories dealing with
memory processing. But none has been confirmed, and the only
thing sleep researchers can agree on is that there is no satisfactory
answer.
Part of the problem is that sleep comprises two very different states:
rapid eye movement sleep (REM), when the eyes flick from side to
side, the brain is very active and most dreaming occurs, and non-
REM, which is a deeper state of unconsciousness. These are so