
used again and again, always co-opted for other uses. If you just take what
you have and reorganize it, you can make something new rather quickly, and I
think that's the way evolution works. And that's one of the surprising things
molecular biology has really revealed.
The puzzle of how an organ as exquisitely complex as an eye could first
evolve was problematic enough that Darwin felt compelled to discuss it at
length in his book "The Origin of Species" in a chapter entitled "Difficulties
of the Theory."
"It's the problem of the incipient stages of useful structures," said Dr.
Stephen Jay Gould, an evolutionary biologist at Harvard University who was the
keynote speaker at the meeting. "We can all see what wings are for when
they're complete wings. But just a few percent of a wing, what good is that?
Darwin's general answer is that it must exist for other purposes, and that
continues as the key theme in the evolution of novelty. You can't get
complexity out of nowhere."
And indeed you don't, as researchers at the National Institutes of Health
studying eye lenses are discovering.
The lens is a remarkable transparent structure filled with proteins called
crystallins, which have been an object of study for more than a century. Found
in great quantities in the lens and perfectly arranged to focus light,
crystallins were long thought to be highly specialized lens proteins that
evolved solely to allow animals to see.
But as researchers studying these proteins are discovering, the evolution
of the lens may have been a lot simpler than was imagined and may begin to
provide lessons in how such complex structures arise in general.
"The story in lens shows that you can evolve complex body parts by
borrowing specialized proteins that are being used for one function for use in
an entirely different function," said Dr. Joram Piatigorsky, chief of the
laboratory of molecular and developmental biology at the National Eye Institute
in Bethesda, Md., and a speaker at the meeting. "I'd rather expect that
similar kinds of things are going on everywhere."
E-Mail Fredric L. Rice / The Skeptic Tank