Study shows how complex functions can originate by random mutation, natural selection

http://www.findarticles.com/cf_dls/m.../article.jhtml

"A long-standing challenge to evolutionary theory has been whether it can explain the origin of complex organismal features. We examined this issue using digital organisms--computer programs that self-replicate, mutate, compete, and evolve. Populations of digital organisms often evolved the ability to perform complex logic functions requiring the coordinated execution of many genomic instructions. Complex functions evolved by building on simpler functions that had evolved earlier, provided that these were also selectively favoured. However, no particular intermediate stage was essential for evolving complex functions. The first genotypes able to perform complex functions differed from their nonperforming parents by only one or two mutations, but differed from the ancestor by many mutations that were also crucial to the new functions. In some cases, mutations that were deleterious when they appeared served as stepping-stones in the evolution of complex features. These findings show how complex functions can or iginate by random mutation and natural selection."

Abstract, "The evolutionary origin of complex features," by Richard E. Lenski, Charles Ofria, Robert T. Pennock, and Christoph Adami

Nature 423, 139-144 (May 8, 2003)

Anyone who wants the full text (plus additional material) can go here: http://myxo.css.msu.edu/papers/nature2003/

My only initial comment is that creationists are typically dismissive of computer simulations. I'll have more to comment after reading the paper (which I'm printing off as I write this).

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Creationism has not made a single contribution to agriculture, medicine, conservation, forestry, pathology, or any other applied area of biology. Creationism has yielded no classifications, no biogeographies, no underlying mechanisms, no unifying concepts with which to study organisms or life. - Botanical Society of America's Statement on Evolution

excellent study, thanks.

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MSci MSc ARCS DIC PhD..... yes, I am bragging.

Biologists find this interesting but isolated from the real world, as this Current Biology article shows.

The article is "Evolution: the erratic path towards complexity" in the
August 19, 2003 issue.

Here's how the article starts:

"A central goal of evolutionary biology is to explain the origin of complex organs - the ribosomal machinery that translates the genetic code, the immune system that accurately distinguishes self from non-self, eyes that can resolve precise images, and so on. Although we understand in broad outline how such extraordinary systems can evolve by natural selection, we know very little about the actual steps involved, and can hardly begin to answer general questions about the evolution of complexity. For example, how much time is required for some particular structure to evolve?"

Now they define "irreducible complexity", and of course can only imagine
the steps required for their formation.

"Complex systems - systems whose function requires many interdependent parts are vanishingly unlikely to arise purely by chance. Darwin’s explanation of their origin is that natural selection establishes a series of variants, each of which increases fitness. This is an efficient way of sifting through an enormous number of possibilities, provided there is a sequence of ever-increasing fitness that leads to the desired feature. To use Sewall Wright’s metaphor, there must be a path uphill on the ‘adaptive landscape.’
The crucial issue, then, is to know what variants are available - what can be reached from where - and what is the fitness of these variants. Is there a route by which fitness can keep increasing? Population genetics is not much help here. Given the geometry defined by mutation and recombination, and given the fitnesses, we can work out how a population will change, simply by following the proportion of different types through time. But understanding how complex features evolve requires plausible models for the geometry of the adaptive landscape, which population genetics by itself does not provide."

They rely on artificial life models and digital organisms to explain
complex structures, but these come up short also.

"Artificial Life models such as Lenski et al.’s are perhaps interesting in themselves, but as biologists we are concerned here with the question of what Artificial Life can tell us about real organisms. The difficulty in answering this is that much work in this field is rather isolated from traditional evolutionary biology."

"In population genetics and evolutionary game theory, we design models to study the success and failure of a predefined set of traits or strategies in the struggle for life. But what are the possible traits? And how well do they succeed in particular environments with particular competitors? These questions are ignored in traditional models - they come in as parameters to be provided by developmental biology and ecology. For understanding the evolution of complex traits this is not satisfactory, because these parameters are themselves shaped by evolution. Evolutionary processes constantly shift the targets of evolutionary optimization, create spatial patterns, turn competitors into mutualists and create new levels of selection. Artificial Life models of such phenomena ... promise to be useful for developing the concepts and techniques to deal with that challenge, but only if they are combined with the insights from almost a century of population genetics."

So we can "hardly begin to answer general questions about the evolution of complexity" and models are "isolated from traditional evolutionary biology."

DNA repair mechanisms are a good example:

DNA needs repair enzymes to prevent catastrophic errors, but the repair enzymes themselves are coded by DNA. How could a DNA strand without the error correction mechanisms survive through very many generations?

well not every strand of DNA suffers catastrophic errors before it reproduces.

the only ones that survived were initially the ones that either got lucky and didn't suffer these errors, or later the ones that repaired themselves (even if they didn't repair themselves perfectly. Those that managed to repair themselves would slowly have become predominant. Say there are 100 of each strand, and 50 of each strand suffer an error. obviously the ones without a repair mechanism cannot reproduce if they broke, but when they replicate, in the next generation we will have 100 strands of original DNA. Now onto those that can repair themselves. Even if only 1 in 50 can repair themselves we now have 51 that can reprodice, so the next generation has 102 strands in it.

Maths explains the rest.

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MSci MSc ARCS DIC PhD..... yes, I am bragging.

Exponential growth rules.

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Greatest Hovind quote of all time, as voted for by members of CF:
"Teaching the pagan religion of evolutionism is a waste of valuable class time and textbook space. It is also one of the reasons American kids don't test as well in science as kids in other parts of the world."