Evolution Of Irreducible Complexity Explained

Apr 12, 2006

Using new techniques for resurrecting ancient genes, scientists have for the first time reconstructed the Darwinian evolution of an apparently "irreducibly complex" molecular system.

The research was led by Joe Thornton, assistant professor of biology at the University of Oregon's Center for Ecology and Evolutionary Biology, and was published in the April 7 issue of Science.

How natural selection can drive the evolution of complex molecular systems – those in which the function of each part depends on its interactions with the other parts--has been an unsolved issue in evolutionary biology. Advocates of Intelligent Design argue that such systems are "irreducibly complex" and thus incompatible with gradual evolution by natural selection.

"Our work demonstrates a fundamental error in the current challenges to Darwinism," said Thornton. "New techniques allowed us to see how ancient genes and their functions evolved hundreds of millions of years ago. We found that complexity evolved piecemeal through a process of Molecular Exploitation -- old genes, constrained by selection for entirely different functions, have been recruited by evolution to participate in new interactions and new functions."

The scientists used state-of-the-art statistical and molecular methods to unravel the evolution of an elegant example of molecular complexity – the specific partnership of the hormone aldosterone, which regulates behavior and kidney function, along with the receptor protein that allows the body's cells to respond to the hormone. They resurrected the ancestral receptor gene – which existed more than 450 million years ago, before the first animals with bones appeared on Earth – and characterized its molecular functions. The experiments showed that the receptor had the capacity to be activated by aldosterone long before the hormone actually evolved.

Thornton's group then showed that the ancestral receptor also responded to a far more ancient hormone with a similar structure; this made it "preadapated" to be recruited into a new functional partnership when aldosterone later evolved. By recapitulating the evolution of the receptor's DNA sequence, the scientists showed that only two mutations were required to evolve the receptor's present-day functions in humans.

"The stepwise process we were able to reconstruct is entirely consistent with Darwinian evolution," Thornton said. "So-called irreducible complexity was just a reflection of a limited ability to see how evolution works. By reaching back to the ancestral forms of genes, we were able to show just how this crucial hormone-receptor pair evolved."

The study's other researchers include Jamie T. Bridgham, postdoctorate research associate in evolutionary biology and Sean M. Carroll, graduate research fellow in biology. The work was funded by National Science Foundation and National Institutes of Health grants and an Alfred P. Sloan Research Fellowship recently awarded to Thornton.

Copyright 2006 by Space Daily, Distributed United Press International

Explore further: Researchers discover low-grade nonwoven cotton picks up 50 times own weight of oil

add to favorites email to friend print save as pdf

Related Stories

'Killer sperm' prevents mating between worm species

18 minutes ago

The classic definition of a biological species is the ability to breed within its group, and the inability to breed outside it. For instance, breeding a horse and a donkey may result in a live mule offspring, ...

Full appeals court upholds labels on meat packages

30 minutes ago

(AP)—A federal appeals court has upheld new government rules that require labels on packaged steaks, ribs and other cuts of meat to say where the animals were born, raised and slaughtered.

Chinese smartphone makers win as market swells

30 minutes ago

Chinese smartphone makers racked up big gains as the global market for Internet-linked handsets grew to record levels in the second quarter, International Data Corp said Tuesday.

Connected devices have huge security holes: study

50 minutes ago

The surge Web-connected devices—TVs, refrigerators, thermostats, door locks and more—has opened up huge opportunities for cyberattacks because of weak security, researchers said Thursday.

Recommended for you

Shrinking dinosaurs evolved into flying birds (w/ Video)

11 hours ago

A new study involving scientists from the University of Southampton has revealed how massive, meat-eating, ground-dwelling dinosaurs evolved into agile flying birds: they just kept shrinking and shrinking, ...

Congressional rift over environment influences public

15 hours ago

American citizens are increasingly divided over the issue of environmental protection and seem to be taking their cue primarily from Congress, finds new research led by a Michigan State University scholar.

Rural loss and ruin can be avoided

18 hours ago

An Australian Reconstruction Development Board needs to be established to help avoid more needless forcing of Australian farmers from their land, a QUT economist has said.

User comments : 0