December 20, 2003
Natural Complexity
Simple chemistry
can provide some surprisingly complex shapes.
By Scott C. Anderson
Living things are so extraordinarily complex, it's
hard to imagine how the happenstance mechanics of Darwinian theory
could have brought them into being. We know that the natural order
of things -- loosely speaking -- is to get old, break down and turn
to crap. So how is it that mere protoplasm has been able to organize
itself so successfully that there has been an unbroken chain of
life on this planet for over 500 million years?
This, of course, is the cry of the creationist as
well. Surely this marvelous complexity is a sign of the hand of
god. The nucleus of a cell, for instance, puts the finest Swiss
watch to shame when it comes to complexity. The nucleus is a sphere
pockmarked with daisy-like pores made of large, intricate proteins.
These pores decide what molecules will be allowed to pass through
the nuclear membrane. A nucleus has hundreds or thousands of these
pores, each acting as a tiny immigration station, checking molecular
identities and letting some through, while sending others back.
A cell, cut away to expose the pore-studded nucleus |
How on earth could such a structure have evolved by
chance alone? Who could possibly believe that any number of tiny
improvements could ever give rise to such a beautiful and useful
structure?
There are people who insist that the number of interdependent
parts of the nucleus proves the case for an "intelligent designer."
They propose that an object like a nucleus is "irreducibly complex."
By that they mean that it's impossible to concoct a believable scenario
of how -- obeying simple laws of nature -- a tiny sphere could combine
with all these pores to form a vital, living membrane. Surely this
arrangement would require powers far outside the hit-or-miss process
of evolution. Just as it is highly improbable that a space shuttle
(or even a humble mousetrap) would sprout naturally from a tree,
how could we presume that a cell nucleus could exist without a designer?
That's why a recent report on "blue water" is so astonishing
(Nature: November 6, 2003).
Native Americans first discovered the blue water,
which seeps out of certain mountains in the western U.S., centuries
ago. Blue water forms naturally when the mineral molybdenite oxidizes.
Water flowing through molybdenite deposits picks up the mineral
and turns a rich blue color. Investigating the mysterious native
reports in the early 1800s, scientists discovered that the blue
water contains molecules with huge clusters of molybdenum and oxygen.
When these clusters get big enough, they form a semi-stable molecular
doughnut containing 154 molybdenum atoms. This is a pretty impressive
feat for such simple chemistry, but this is just the beginning of
the story.
It turns out that these doughnuts like to hang out
together, and when there are a thousand of them or so they join
up, spontaneously forming a hollow sphere. To a biologist, this
should be a familiar structure.
Although smaller than a cellular nucleus, it
has remarkable similarities. It has a naturally spherical shape,
and it is composed of complex circular, pore-like subunits.
Among other things, it shows how incredibly
complicated objects can be created with ordinary inorganic chemistry.
This represents a breakthrough in the study of nanotechnology, because
molecules of this size and structure could be very useful for hundreds
of applications. But from an evolutionary point of view, it also
represents an exciting glimpse into what the actual building blocks
of biology might be. It now appears that they may already have as
much complexity as we would ordinarily grant to biological items.
This pretty blue ball isn't alive, of course. And
whether it has any connection at all to an actual nucleus is dubious.
But it shows us how little we know about natural complexity. That
a batch of molecular doughnuts would self-assemble into a tiny sphere
is a wake-up call to those who feel that ordinary chemistry will
not suffice to explain life. As this discovery amply demonstrates,
a startling amount of complexity is simply par for the course.
Copyright © 2000-2004 by Scott Anderson
For reprint rights, email the author:
Scott_Anderson@ScienceForPeople.com
Here are some other suggested readings about complexity:
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