dawn of animal vision discovered

Dawn Of Animal Vision Discovered

When skeptics of evolution attack Darwin's well founded theory they

often point to the complexity of the human eye. "How could random

mutation and natural selection account for such a complex organism as

the human eye", they argue. "How could the separate parts come

together through this process, since none of these parts on their own

make vision possible?"

Well, some scientists at the University of California, Santa Barbara

have come up with the answer.

The findings are published in this week's issue of the scientific

journal PLoS ONE. The scientists studied the aquatic animal Hydra, a

member of Cnidaria, which are animals that have existed for hundreds

of millions of years. The authors are the first scientists to look at

light-receptive genes in cnidarians, an ancient class of animals that

includes corals, jellyfish, and sea anemones.

"Not only are we the first to analyze these vision genes (opsins) in

these early animals, but because we don't find them in earlier

evolving animals like sponges, we can put a date on the evolution of

light sensitivity in animals," said David C. Plachetzki, first author

and a graduate student at UC Santa Barbara. The research was conducted

with a National Science Foundation dissertation improvement grant.

"We now have a time frame for the evolution of animal light

sensitivity. We know its precursors existed roughly 600 million years

ago," said Plachetzki.

Senior author Todd H. Oakley, assistant professor of biology at UCSB,

explained that there are only a handful of cases where scientists have

documented the very specific mutational events that have given rise to

new features during evolution.

Oakley said that anti-evolutionists often argue that mutations, which

are essential for evolution, can only eliminate traits and cannot

produce new features. He goes on to say, "Our paper shows that such

claims are simply wrong. We show very clearly that specific mutational

changes in a particular duplicated gene (opsin) allowed the new genes

to interact with different proteins in new ways. Today, these

different interactions underlie the genetic machinery of vision, which

is different in various animal groups."