Sun, 21 Nov 1999 09:52:29 -0800
>From the New York Times science section today:
Pondering Next Rung on the Evolutionary Ladder
By MALCOLM W. BROWNE
If evolution is still unfolding, and most scientists believe it is,
just how complex an organism could the evolutionary process create,
before hitting some fundamental limit?
People leading independent lives, as we do today, might not be the end
of the human evolutionary line. Is it possible that one day we might
subordinate impulses toward individual behavior and merge into an
organic community, a kind of human superbeing with its own sense of
No one can predict what might happen in
the next million years or so, but it's fun to
One thing is certain: an important rung in the
evolutionary ladder was the transition from
single-celled to multicellular existence. And
that rung may have been the first of many
along an endless road to complexity.
How to account for that first step, which our remote ancestors took eons
ago, still poses many puzzles.
But however the progression from individual independence to collective
life may have unfolded, it seemed to have required some kind of chemical
internet, by which independent cells communicated with one another and
learned to enhance their collective well-being by acting in concert.
Surely, the human race has already hit upon something like that.
A fundamental step in the process entails inducing many independent
individuals to join together and march in lockstep. Scientists in Denmark
recently discovered an intriguing new manifestation of this behavior in
cells of baker's yeast -- the kind that makes bread dough rise.
Yeast cells ordinarily lead lives independent of one another as they leaven
bread dough, ferment grape juice or cause yeast infections. But a team
led by Dr. Sune Dano of the University of Copenhagen reported in a
recent issue of Nature that they had engineered a yeast community in
which all the cells produced synchronous pulses of a chemical called
NADH, one of the substances created when an organism breaks down
sugar to generate energy.
This chemical oscillation of yeast, in which concentrations of NADH
rhythmically rise and fall, has been observed before. But the trick in this
case was finding a way to keep the oscillations going indefinitely. To do
this, Dr. Dano said in an interview, the scientists exploited a theory for
which the Belgian chemist Ilya Prigogine was awarded the 1977 Nobel
Prize in Chemistry. In simple terms, Dr. Prigogine showed that despite
the laws of thermodynamics that make most physical processes run
downhill, an upward march toward increasing complexity can be
achieved in "open" systems.
Open systems, which Dr. Prigogine dubbed "dissipative structures," are
those to which energy is constantly added and waste (in the form of
entropy, a measure of a system's disorder) is removed. Trees and people
are examples of dissipative structures.
In Dr. Dano's application of this idea, a glass tube containing yeast cells
was constantly replenished with fresh cells, along with glucose and
cyanide, while waste matter and excess liquid were constantly removed
and discarded. When conditions were adjusted precisely, clock-like
chemical oscillations were induced in the yeast culture, and they
continued indefinitely, as long as fresh yeast cells, glucose and cyanide
were continuously added in the right amounts and excess fluid was
Collective chemical oscillations in yeast colonies, the scientists concluded,
"suggest an evolutionary path from unicellular to multicellular behavior."
Yeast cells are not the only creatures that routinely cross the boundary
between one-celled and multicellular existence.
Single-celled bacteria can form huge mat-like colonies that live almost
like multicellular creatures, and evidence that such mats existed even
during the earth's early years has been found in ancient rock.
Soil amoebas -- highly complex single-celled organisms -- live
independently from one another when there is plenty to eat. But in
impoverished environments they join together to produce spores, and in
their collective state they can move relatively fast, sensing light and
warmth as guides to food supplies.
The creation of collective beings from single-celled organisms has been
going on a long time.
Millions of years ago, shells of single-celled animals (called nummulites)
were deposited in huge layers in the limestone later used by ancient
Egyptians in building the Sphinx.
Among the oldest multicellular animals with an apparent sense of self are
the sponges, which can exist either as independent, freely moving cells or
as huge assemblages of cells held together by skeletons made of protein
and minerals, and containing complex food-filtering plumbing. Once
thought to have no power of locomotion, sponges have been shown to
be capable of creeping over a surface at a speed of a few millimeters a
day to seek out food.
At higher levels of organization, many individual insects (ants and bees for
example) are essentially mere components of the superbeing represented
by the colony or hive.
Communication provides the coherence allowing such superbeings to
function; the complicated dance steps used by bees to inform their
hive-mates of the directions and distances to food sources serve as their
Higher still on the complexity ladder are birds that flock and fish that
swim in perfectly choreographed collective patterns.
One of the strangest creatures is the naked mole rat, a nearly blind little
animal living in East African deserts that spends its life underground within
a "eusocial" organization, as biologists call it, more like that of insects than
of other mammals. Each individual in a mole rat colony serves as a cog in
a big wheel; only one female in a colony produces young, and the other
animals have the specialized jobs of searching for food, caring for the
young, guarding against predators and house-cleaning.
For a naked mole rat, the sole focus of existence is the colony; individual
life outside the colony is meaningless.
Aldous Huxley's 1932 novel, "Brave New World," envisions a human
society in which individuals are programmed before birth as "Alpha-plus
intellectuals," "Epsilon-minus morons" or any of the intermediate levels,
predestining everyone to specific occupations in a rigidly structured
society, not unlike that of mole rats.
Today, the world has sufficient "carrying capacity" to sustain its human
population in the guise of individuals capable of independent action. But
might a day come when we run out of necessities and are forced to
evolve toward a eusocial superbeing?
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