September 5, 1999
The Hidden Traps in Fooling Mother Nature
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By NICHOLAS WADE
ow that researchers have shown
that mice can be made smarter, a
whole world of opportunities opens
up. Those long-neglected inventors
of smarter mousetraps will at last get their
calls returned. Smarter cats will be needed.
And everyone will have a list of humans who
might benefit, starting perhaps with the
baseball umpires or, in the case of most
evolutionists, with the Kansas Board of Education.
Pleasant as it may be to contemplate a
smarter world, there are serious quandaries in enhancing human abilities, as well as
in trying to raise the intelligence of animals,
possibilities raised last week by the Princeton biologist Joe Z. Tsien and his colleagues
when they announced they had developed a
genetically smarter strain of mice.
In mice, monkeys and probably humans,
nature has engineered a deliberate fading of
memory with age. The brain cell receptor
that helps associate two events -- the basic
mechanism of memory -- is made of components that change over a life span, making the receptor less efficient in older animals. It is this process that was counteracted in Dr. Tsien's mice. He genetically engineered the mice so that their brain cells
produced more copies of the youthful component of the memory receptor, thus enhancing its performance.
The receptor was souped up in brain cells
throughout the
mice's forebrain
and hippocampus,
a brain module
that helps mice remember places
(and humans to recall places and
faces).
The altered
mice did better
than normal mice
on six standard
tests of rodent intellectual performance, like remembering where to
find a hidden platform when
dropped into a bucket of murky water, or
recognizing new objects. Because the improvement was consistent in all the tests,
for which the mice had to use many different areas of the brain, Dr. Tsien concluded
that in improving the basic mechanism of
memory he had also enhanced the mice's
learning ability and general intelligence.
Dr. Tsien and other scientists are far
from sure that tweaking the memory receptor would be similarly helpful in the more
complicated human brain. After all, with too
retentive a memory you might clutter up
your mind with all kinds of things you'd be
better off forgetting. Still, scientists agree
that the receptor is a promising place for
intelligence enhancement to start.
But would the improvement of human
acumen dangerously flout nature's wisdom? After all, intelligence is so precious
for survival that surely nature makes every
animal as smart as possible without transgressing some pivotal balance.
This doesn't seem to be the case, however,
at least with laboratory mice. Dr. Tsien's
strains are smarter than their normal cousins, without any visible drawback.
And behaviorally, modern man is so new a species
-- 50,000 years is the blink of an eye in
evolutionary time -- that perhaps the forces
of natural selection have scarcely had the
chance to make the most of the human
brain's capacities.
Still, genetic engineers must surely pause
at the fact that nature has designed memory
to become less retentive with age.
The
danger of tampering with this system is that
the brain's memory storage room could
quickly be overwhelmed if learning were to
continue at the same rate in adult life as in
youth, suggests Dr. Charles Stevens, a neurobiologist at the Salk Institute in La Jolla,
Calif. He believes the brain's capacity, vast
as it is, must have limits. The human brain has
100 billion neurons, and each neuron makes
about 1,000 connections with other neurons, giving a potential 100 trillion units of memory. "So
there is enormous storage capacity, but we
don't know how much we need," Dr. Stevens
said.
Even if the limit of that storage capacity is
never reached in a human lifetime, the increasing access time needed to scan a growing store
of knowledge may be one reason why nature
arranges for information to be acquired more
slowly once the youthful thirst for knowledge
has passed. What a powerful threat to deploy
against one's children -- learn it or lose it.
Despite the risk of running out of space on
one's mental hard drive, the temptation to try to
enhance intelligence by promoting the youthful
form of the memory receptor will doubtless
prove irresistible.
Drugs might be developed to
target the nerve cell system that Dr. Tsien
altered by genetic means. Gene therapy could
one day supply smart genes to an embryo -- or
even to adults, since the hippocampus is one of
the few areas of the brain that generates new
cells throughout adult life.
Three categories of people might benefit: the
medically ill, the elderly and everybody else.
Ethicists see no problem in trying to treat
memory deficits in patients with brain diseases,
which would be no different from any other
medical intervention. Helping older people remember better is also likely to be uncontroversial, "because in our culture we see old age as
something like a disease rather than as natural
life process," said Dr. Victoria Sharpe, a bioethicist at the Hastings Center in Garrison, N.Y.
drug to enhance the intelligence of
healthy individuals sounds great for
job interviews or quiz programs. But if
the smart pill were costly, it could
worsen social inequities. And such a drug could
easily be abused by parents. "I think we will
have to think through our social policies very
carefully so we don't get into an enhancement
race among parents and don't in effect develop
a new kind of child abuse," said Dr. Leroy
Walters, director of the Kennedy Institute of
Ethics at Georgetown University.
Dr. Walters said it would be "a plausible and
morally justifiable application of genetic techniques" to raise the intelligence of a child with
very low I.Q. scores, because that could be
regarded as remedial, but enhancing the I.Q. of
someone at or above the mean would be much
more controversial, in his view.
The ethical implications extend beyond humans. Well before anyone tries to increase
human intelligence, the technique will be tested
in monkeys or chimpanzees. A smarter chimp
might help answer the enduring question of
whether animals are conscious or whether consciousness is only attained by brains with the
capacity for language. But how much smarter
can chimpanzees get before they merit, or even
demand, special rights?
"Say we produce a chimp that is more intelligent than people," said Dr. Sharpe. "I think we
would probably just try to enslave it rather than
welcome it into the human community. It may
be a cynical view but I don't think we are very
good at according moral status to non-humans."
Pioneers like Dr. Tsien are eager to explore
the new possibilities created by genetic engineering. Nature may be wise, but it often doesn't act in the individual's best interest, he notes.
The body's cells don't have to rust and wear out
like cars: they could renew themselves indefinitely. Since nature lets us die, Dr. Tsien believes, it may also have neglected to make
humans as smart as they can be .
He finds it hard to understand the recent
flurry of apprehension about human cloning,
because a clone, being an exact genetic copy,
adds nothing new to the world. But making an
individual more intelligent would be novel and
interesting. "Everyone wants to be smart," he
said.
