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Author: adonsant Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 25064  
Subject: Re: A question to atheists. Date: 1/10/2008 5:07 PM
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Anyway...he says the following question stumped Dawkins. Not that I accept Dawkins as a benchmark of scientific knowledge, but he is a biologist. He was asked to identify one verifiable example of an organism increasing its complexity (the implication being that this is what is required if we are to believe in descent from single-celled organisms to the multi-celled organisms such as chimps and dolphins and us). This may be a nonsense question, or it may be that there's an excellent answer. I don't know enough to argue either way. We infer a lot from the fossil record, but even then if you read carefully the paleontologists use a lot of vague language (e.g. "may have", "appears to"). Some of that I'm sure is typical scientific caution, but some of it may simply be because it is NOT conclusive. Interested in your input on this question. This appears to relate to changes in (for example) the phylum or genus leading to new species, if I understand the intent correctly.

It's not so much a "nonsensical" question... but one that allows the asker to wiggle out of any answer by claiming that the increase in complexity you've shown is "not big enough." Small increases in complexity are easy to show. Antibiotic resistance is often caused by the evolution of a new catalytic or transport activity, a increase in the biochemical complexity of the organism. Creationists will argue that they want structural complexity and not biochemical complexity. But this ignores the fact that the two are similar, if not identical. In both cases, you want a mutated protein to bind to a novel target. Whether the target is a protein or another type of molecule seems irrelevant.

Development of new cell-cell interactions are assumed to be important in the evolution of increased complexity. The evolution of new interactions between cells has also been observed [Nature 445, 533-536 (1 February 2007)], though in this case the evolved interaction is between two species of bacteria. I like it because it's an example where mutation of a single protein has such a profound effect on creating a relationship between the two species and increases their combined productivity. There are also interesting examples of the evolution of cooperation in the bacterium Myxococcus xanthus [Nature 441, 310-314 (18 May 2006); Nature 425, 75-78 (4 September 2003)]. However, these don't produce "true" multicellular organisms with differentiated cell types.

One interesting reconstruction of the evolution from a single-celled organism to a multicellular organism is the green algae, Volvox. Given it relatively late rise to multicellularity (the last 50 million years or so) and the abundance of closely related species within the order Volvocales, one can construct of model of its evolution in a series of plausible small steps and identify examples of intermediates at each step in related organisms (Herron MD, Michod RE. Evolution Int J Org Evolution. 2007 Nov 19 [Epub ahead of print]). As you can probably guess, compressing 50 million years of evolution into a laboratory experiment that would satisfy the "verifiable" requirement is probably next to impossible with the three year grant cycle. However, if someone is willing to front 10 million years of research funding, I'll give it a shot. ;-)

I was interested to hear him say today that evolution via natural selection is an excellent theory regarding why we have such wide varieties within a "kind". Sounded like the "can't get a cat from a dog" argument, though he didn't specifically say that.

This commonly comes up, and I guess I should spend a few minutes on it since sooner or later it becomes central to the discussion. Creationists like to differentiate between evolving new species and evolving new genera, phyla, or some other classification level. What they seem to miss is that the classification scheme we use beyond species (and even defining different species itself is often fuzzy) is entirely arbitrary. We have 7 levels (kingdom, phylum, class, order, family, genus, species), but we could have had 14 or 3 or 100 or 42, etc. The classification system depends on when we began classifying organisms. To illustrate, before DNA sequencing was available, bacteria were generally classified by biochemical analysis. In the lab, we can take a particular bacteria, say, E. coli, and grow it under selective pressures to allow it to use novel carbon sources, resist new antibiotics, etc. But, no matter how long we do this and how different biochemically it becomes from the ancestral bacteria, we're still going to call it a strain of E. coli. It's unlikely that it would ever be assigned a new genus. We know exactly where it came from and the rRNA sequence would put it square in Escherichia.

To look at it another way, consider the following phylogeny, with time since the last common ancestor for any two species being on the vertical (horizontal distance is unimportant). LCA is the last common ancestor of all of these species, and all of the species are alive at the time we classified them. (I apologize if this doesn't render properly ahead of time. I had to do some magic with spaces, and I'm not sure if it will translate well from the Mac to the PC.)

                      LCA
           ____________|____________
     ______|______            _____|____
     |           |            |        |
     |           |         ___|___     |
  ___|____    ___|___   ___|__   |  ___|__
__|_  |  |  __|_  __|_  |  __|_  |  |  __|_
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
a  b  c  d  e  f  g  h  i  j  k  l  m  n  o


Genus 1 consists of a, b, c, and d.
Genus 2 consists of e, f, g, and h.
Genus 3 consists of i, j, k, and l.
Genus 4 consists of m, n, and o.
All four genera are within the same family.

Now, consider what would have happened had we classified the organisms halfway between the LCA and the 'modern' organisms. Here's how the tree would have looked:

     LCA
  ____|____
__|__   __|__
|   |   |   |
1   2   3   4


At that point in time we would likely have classified these as four species in one genera, rather than as the founders of four genera.

The apparent contradiction, of course, is merely an artifact of the classification system. You don't evolve a "new phylum." You have a species that evolves a particular trait that someone later uses to categorize the species that branch off of it.

-Anthony
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