Life’s Origins 167many bacteria use to secrete toxins. This example of co-option is regarded as strong evidence
against Behe’s example of “irreducible complexity.”
Probability and the Origin of Life
In what manner the mental powers were first developed in the lowest organisms, is as
hopeless as how life itself first originated. These are problems for the distant future,
if they are ever to be solved by man.
—Charles Darwin, The Descent of ManAs this quote shows, even Darwin was reluctant to speculate in print about the origin of
life (although he did so privately in his letter to Hooker). The evidence of evolution from
the fossil record since life originated is very clear (as the next few chapters shall show), but
scientists must speculate and use chemical and physical experiments to try to reconstruct
the origin of life. Nonetheless, we have seen that scientists have made enormous strides in
the past seven decades, from the first Urey-Miller experiment to the many abiotic syntheses
of amino acids; to the many mechanisms that allow us to assemble complex polymers of
proteins, lipids, carbohydrates, and nucleic acids from simpler components using templates
like zeolites, clay, or pyrite; to Margulis’s endosymbiotic origins of the eukaryotic cell. Not
every problem has been solved or every answer revealed, but the research on the origins of
life is a relatively young, healthy field of science with much more to learn and much more to
do. Given the progress that has been made so far, we seem to be close to having many of the
steps in the origin of life nailed down scientifically.
Yet you would never know this from the creationist literature. The creationists view
the origin of life as a weak spot in evolutionary theory and love to attack it because it is
complicated and difficult to discuss or defend in a debate format. They know that most of
their readers have no science background, are impressed and baffled by all that talk of cells
and biochemistry, and are easily persuaded to believe simplistic arguments about stuff they
don’t intuitively understand. Typically, creationists wow the audience with a presentation
on the complexity of the cell and its many biochemical mechanisms and challenge the evo-
lutionist to assemble this fantastically complex system by chance.
As many others have shown, there are many simple clear-cut answers to this challenge.
First of all, we have just run through the steps that show us how to gradually build life from
the simplest chemicals to amino acids to proteins and other polymers to prokaryotic cells
to eukaryotic cells, all using relatively small steps that could be driven by natural selec-
tion. None of the steps require extraordinary conditions, and none are outside the realm of
plausibility. In most cases, each step can either be simulated in the lab or seen in examples
of the process (such as endosymbiosis) still working in nature today. Second, no evolution-
ary biologist says that this all arose by chance. As we discussed in chapter 2, chance may
supply the raw material of variation on which selection acts, but selection is definitely a
nonrandom agent (the “monkey with the word processor” analogy we used earlier). Cre-
ationists will point to some complex biochemical pathway and claim that it is “irreducibly
complex” and cannot be built by natural selection. But many biochemists have torn these
arguments apart because nearly every biochemical process or pathway exists in multiple
forms from simple to complex, and it is easy to show that just by adding on a few steps here