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 Probably the most important common denominator of evolutionary theory and neuroscience is degeneracy. The degeneracy found in gene networks and the degeneracy found in the organization of brains. See e.g. 2001 PNAS article by nobel laureate Gerald Edelman. In it he writes:
[Degeneracy] is both necessary for, and an inevitable outcome of, natural selection. In other words: if there were no evolution, there would be no degeneracy.
Therefore, creationists will have to explain why there is degeneracy if there is no evolution.
In the latest issue of ScienceExpress, there is an absolutely fantastic study by Tagkopoulos et al. from Princeton showing how evolution leads to gene-networks which are both anticipatory and degenerate. From the abstract:
We show that in silico biochemical networks, evolving randomly under precisely defined complex habitats, capture the dynamical, multi-dimensional structure of diverse environments by forming internal models that allow prediction of environmental change. We provide evidence for such anticipatory behavior by revealing striking correlations of Escherichia coli transcriptional responses to temperature and oxygen perturbations — precisely mirroring the co-variation of these parameters upon transitions between the outside world and the mammalian gastrointestinal-tract. It is interesting to note that in the article, the authors confuse degeneracy with "redundancy" which, of course, it a very different thing. Notwithstanding, their meticulously designed simulations and experiments have elucidated how amazingly intricate and complex comparatively simple organisms can become if you allow them to evolve and that degeneracy is both a prerequisite and an outcome of evolution.
This paper joins one in Nature I already reported about. It also shows how the complex, degenerate properties of gene networks underscoring the importance of the ubiquitous concept of degeneracy.
Together, these two papers have the potential to develop into two of the most important papers in all of biology. They are required reading for everyone with an interest in evolution.
To close the loop to neuroscience: the degeneracy which is displayed in evolved gene networks is reflected in the evolved organization of brains. Different network configurations can produce the same behavioral output (Prinz et al. Nature Neuroscience, 2004). This degeneracy in the brain also leads to something not explicitly shown in gene-networks (AFAIK): the same neuronal network can produce different behaviors even under identical external circumstances (our own study on spontaneous behavior and Briggman et al, Science, 2005). It has been known for quite some time now that spontaneous behavioral variability has enormous fitness benefits and is affected in a variety of psychiatric disorders. This is now not so surprising any more. It's all starting to make perfect sense now.
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Comments
achard
Guest
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09 May : 11:27
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I'm sorry but I know well the work of Prinz and I don't see how it relates to evolution. We're dealing here with homeostasis, i.e. internal mechanisms that tune channel expression to obtain the desired output. And these mechanisms don't require evolution (I mean, not more than old fashioned channel expression, I have no doubt that all these mechanisms are the product of evolution but I guess that's not what you were meaning).
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bjoern
Comments: 56
Location: Berlin, Germany
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09 May : 23:30
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Ah, good point! Maybe I should have made that point clearer! I guess what I was trying to say was that one can see degeneracy also at the level of the nervous system. Now why would that be? Adaptive behavior is one level of selection and therefore you would expect degeneracy as an outcome of selection. Nervous systems control behavior and they are clearly degenerate (see the Edelman reference). Degeneracy means that two structurally different components can produce the same function. In nervous systems this, I think, also entails the inverse: that the same component an also produce different functions. This is what one can see in the work of Prinz et al., Briggman et al. and our work. The sort of homeostasis you refer to is thus an effect of degeneracy: the different biophysical and network properties of the SGN pacemaker neurons produce the same function: slow, medium and fast pyloric rhythms.
Does that make any sense now? I'd be very interested to hear counter-arguments!
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achard
Guest
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10 May : 08:00
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First of all, my first comment was a bit rough, I'm sorry. That's the blog format I guess. I come here daily, I cite some of your posts in my own blog (in french) and therefore I felt almost "at home" or at least authorized to be as direct as during a lab meeting. 
That said, my point was the following. For long time, we envisioned channel expression as a fixed mechanism: DNA dictates the amount of such and such channel on the cell membrane. In that framework, I agree with you, degeneracy is the result of evolution (or at least of the "survival of the fittest" mechanisms).
Nowadays, a bunch of experimental and theoretical work shows that there exists some homeostatic mechanism inside neurons. This mechanism is far from being understood but its effects are clear : if you deviate a neuron from its desired electrophysiological behavior, it will underexpress or overexpress some of its ionic channels to fall back on its target activity.
With such a mechanism hard-coded in the neuron, I don't see the need for evolution to explain degeneracy: start with 2 neurons with 2 different initial conditions, or 2 neurons in slightly different environnements and the homeostatic mechanism will bring you to 2 different solutions for the same behavior.
(Once again, i have no doubt that the homeostatic mechanism itself is not the product of an intelligent design...)
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achard
Guest
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10 May : 08:06
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PS: 2 good reviews of homeostasis
E Marder, JM Goaillard - Nat Rev Neurosci, 2006
G Davis - Annu Rev Neurosci, 2006
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