Posted on 04/07/2006 9:54:33 AM PDT by neverdem
By reconstructing ancient genes from long-extinct animals, scientists have for the first time demonstrated the step-by-step progression of how evolution created a new piece of molecular machinery by reusing and modifying existing parts.
The researchers say the findings, published today in the journal Science, offer a counterargument to doubters of evolution who question how a progression of small changes could produce the intricate mechanisms found in living cells.
"The evolution of complexity is a longstanding issue in evolutionary biology," said Joseph W. Thornton, professor of biology at the University of Oregon and lead author of the paper. "We wanted to understand how this system evolved at the molecular level. There's no scientific controversy over whether this system evolved. The question for scientists is how it evolved, and that's what our study showed."
Charles Darwin wrote in The Origin of Species, "If it would be demonstrated that any complex organ existed which could not possibly have formed by numerous, successive, slight modifications, my theory would absolutely break down."
Discoveries like that announced this week of a fish with limblike fins have filled in the transitions between species. New molecular biology techniques let scientists begin to reconstruct how the processes inside a cell evolved over millions of years.
Dr. Thornton's experiments focused on two hormone receptors. One is a component of stress response systems. The other, while similar in shape, takes part in different biological processes, including kidney function in higher animals.
Hormones and hormone receptors are protein molecules that act like pairs of keys and locks. Hormones fit into specific receptors, and that attachment sends a signal to turn on — or turn off — cell functions. The matching of hormones and receptors led to the question of how new hormone-and-receptor pairs evolved, as one without the other would appear to...
(Excerpt) Read more at nytimes.com ...
According to Darwinian theory, complexity evolves by a stepwise process of elaboration and optimization under natural selection. Biological systems composed of tightly integrated parts seem to challenge this view, because it is not obvious how any element's function can be selected for unless the partners with which it interacts are already present. Here we demonstrate how an integrated molecular system—the specific functional interaction between the steroid hormone aldosterone and its partner the mineralocorticoid receptor—evolved by a stepwise Darwinian process. Using ancestral gene resurrection, we show that, long before the hormone evolved, the receptor's affinity for aldosterone was present as a structural by-product of its partnership with chemically similar, more ancient ligands. Introducing two amino acid changes into the ancestral sequence recapitulates the evolution of present-day receptor specificity. Our results indicate that tight interactions can evolve by molecular exploitation—recruitment of an older molecule, previously constrained for a different role, into a new functional complex.
so, ah... you just feeling frisky, or do you actually *want* to get a whole lot of posts calling you a fool, a marxist, and a god-hater?
It's absolutely amazing that almost 150 years later using advanced science that Darwin could never have dreamed about, every new discovery only proves him right while a century and a half of nonstop distractions still haven't come up with the one single piece of evidence that would break his theory down.
Good point
With my tagline?
Evolution of 'irreducible complexity' explained.
Two New Discoveries Answer Big Questions In Evolution Theory.
The system is molecular, no doubt about it. They need to focus a little sharper on cell walls, or organelle walls, and less on DNA. The brain is in the cell wall, not the nucleus.
These sort of variations where an amino acid or two change causes slight differences in orders of potency for related ligands is ubiquitous. I'll read this and again thanks for the post.
What was more interesting is they seem to be directly addressing Behe.
that sort of thing has never stopped the Raging Luddites yet.
Thanks for the links.
FReepmail me if you want on or off my health and science ping list.
You just wait. As soon as the guys at AIG raise a few hundred million dollars more, they will mount an expedition and find Noah's Arc.
Cheers!
origin?
Evolution as a biological theory shows its utulity in explaining changes between proximal ancestors and descendants. It offers little to nothing about the origin of living creatures.
Hmmm....this article starts with a completed cell. How did something more complex than anything man has every built just come into existence on a lifeless planet? The NYT is no more credible on the subject of science than it is on politics.
Creationists say that there is a Creator God who created the first matter, energy, and information. An all-powerful personal God willed all of that into existence, in a useable complex form. Since that beginning, speciation has taken place, but within boundaries. That is not anti-scientific...no more so than saying many billions of years ago, at the Big Bang, all of the matter, energy, and information in the universe exploded from nothing, randomly, into existence. And all the complex systems of the universe assembled themselves.
That takes a lot of faith...more faith than I as a creationist can muster.
Evolution is their god?
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