The New York Times
August 22, 2005
In Explaining Life's Complexity, Darwinists and Doubters
By KENNETH CHANG
At the heart of the debate over intelligent design is this question:
Can a scientific explanation of the history of life include the
actions of an unseen higher being?
The proponents of intelligent design, a school of thought that some
have argued should be taught alongside evolution in the nation's
schools, say that the complexity and diversity of life go beyond what
evolution can explain.
Biological marvels like the optical precision of an eye, the little
spinning motors that propel bacteria and the cascade of proteins that
cause blood to clot, they say, point to the hand of a higher being at
work in the world.
In one often-cited argument, Michael J. Behe, a professor of
biochemistry at Lehigh University and a leading design theorist,
compares complex biological phenomena like blood clotting to a
mousetrap: Take away any one piece - the spring, the baseboard, the
metal piece that snags the mouse - and the mousetrap stops being able
to catch mice.
Similarly, Dr. Behe argues, if any one of the more than 20 proteins
involved in blood clotting is missing or deficient, as happens in
hemophilia, for instance, clots will not form properly.
Such all-or-none systems, Dr. Behe and other design proponents say,
could not have arisen through the incremental changes that evolution
says allowed life to progress to the big brains and the sophisticated
abilities of humans from primitive bacteria.
These complex systems are "always associated with design,"
Dr. Behe, the author of the 1996 book "Darwin's Black Box,"
said in an interview. "We find such systems in biology, and since
we know of no other way that these things can be produced, Darwinian
claims notwithstanding, then we are rational to conclude they were
It is an argument that appeals to many Americans of faith.
But mainstream scientists say that the claims of intelligent design
run counter to a century of research supporting the explanatory and
predictive power of Darwinian evolution, and that the design approach
suffers from fundamental problems that place it outside the realm of
science. For one thing, these scientists say, invoking a higher being
as an explanation is unscientific.
"One of the rules of science is, no miracles allowed," said
Douglas H. Erwin, a paleobiologist at the Smithsonian Institution.
"That's a fundamental presumption of what we do."
That does not mean that scientists do not believe in God. Many do. But
they see science as an effort to find out how the material world
works, with nothing to say about why we are here or how we should
And in that quest, they say, there is no need to resort to
otherworldly explanations. So much evidence has been provided by
evolutionary studies that biologists are able to explain even the most
complex natural phenomena and to fill in whatever blanks remain with
This is possible, in large part, because evolution leaves tracks like
the fossil remains of early animals or the chemical footprints in DNA
that have been revealed by genetic research.
For example, while Dr. Behe and other leading design proponents see
the blood clotting system as a product of design, mainstream
scientists see it as a result of a coherent sequence of evolutionary
Early vertebrates like jawless fish had a simple clotting system,
scientists believe, involving a few proteins that made blood stick
together, said Russell F. Doolittle, a professor of molecular biology
at the University of California, San Diego.
Scientists hypothesize that at some point, a mistake during the
copying of DNA resulted in the duplication of a gene, increasing the
amount of protein produced by cells.
Most often, such a change would be useless. But in this case the extra
protein helped blood clot, and animals with the extra protein were
more likely to survive and reproduce. Over time, as higher-order
species evolved, other proteins joined the clotting system. For
instance, several proteins involved in the clotting of blood appear to
have started as digestive enzymes.
By studying the evolutionary tree and the genetics and biochemistry of
living organisms, Dr. Doolittle said, scientists have largely been
able to determine the order in which different proteins became
involved in helping blood clot, eventually producing the sophisticated
clotting mechanisms of humans and other higher animals. The sequencing
of animal genomes has provided evidence to support this view.
For example, scientists had predicted that more primitive animals such
as fish would be missing certain blood-clotting proteins. In fact, the
recent sequencing of the fish genome has shown just this.
"The evidence is rock solid," Dr. Doolittle said.
Intelligent design proponents have advanced their views in books for
popular audiences and in a few scientific articles. Some have
developed mathematical formulas intended to tell whether something was
designed or formed by natural processes.
Mainstream scientists say that intelligent design represents a more
sophisticated - and thus more seductive - attack on evolution. Unlike
creationists, design proponents accept many of the conclusions of
modern science. They agree with cosmologists that the age of the
universe is 13.6 billion years, not fewer than 10,000 years, as a
literal reading of the Bible would suggest. They accept that mutation
and natural selection, the central mechanisms of evolution, have acted
on the natural world in small ways, for example, leading to the decay
of eyes in certain salamanders that live underground.
Some intelligent design advocates even accept common descent, the
notion that all species came from a common ancestor, a central tenet
Although a vast majority of scientists accept evolution, the Discovery
Institute, a research group in Seattle that has emerged as a
clearinghouse for the intelligent design movement, says that 404
scientists, including 70 biologists, have signed a petition saying
they are skeptical of Darwinism.
Nonetheless, many scientists regard intelligent design as little
more than creationism dressed up in pseudoscientific clothing. Despite
its use of scientific language and the fact that some design advocates
are scientists, they say, the design approach has so far offered only
philosophical objections to evolution, not any positive evidence for
the intervention of a designer.