Network Genetics, Network Evolution

Genetics and evolution are complex and inter-linked subjects.  That’s not to say the lay-person can’t understand them – the basic principles under which they work are simple enough – it’s just that once you start to focus your view down into the details the complexity emerges.  Let me give you an example.  Eye colour.

The colour of our eyes as humans is clearly linked to our genes and is, in some respects, a hereditary trait.  But to think of there being ‘a gene for blue eyes’ or ‘a gene for brown eyes’ is inaccurate.  The link between the genotype (the genes) and the phenotype (what we can observe in the organism) is complex.  There are a number of genes that seem to influence the colour of our eyes and in many respects the absence of a gene as well as it’s presence can determine the final colour we see.

Science blogger PZ Myers gives a good description of the complexities of mapping the phenotype from the genotype.  He suggests that Evolution 101 is something like:

Evolution proceeds by mutation and selection. A novel mutation occurs in a gene that gives the individual inheriting it an advantage, and that person passes it on to their children who also gets the advantage and do better than their peers, and leave more offspring. Given time, the advantageous mutation spreads through the population so the entire species has it.

Then, as we make it more complex, Evolution 201 then starts to introduce us to the finer grain of detail and show us more of what is really going on:

First, [Evolution 101 is] not exactly wrong — it’s more like taking one good explanation of certain kinds of evolution and making it a sweeping claim that that is how all evolution works. By reducing it to this one scheme, though, it makes evolution far too plodding and linear, and reduces it all to a sort of personal narrative. It isn’t any of those things. What’s left out in the 101 story, and in creationist tales, is that: evolution is about populations, so many changes go on in parallel; selectable traits are usually the product of networks of genes, so there are rarely single alleles that can be categorized as the effector of change; and genes and gene networks are plastic or responsive to the environment. All of these complications make the actual story more complicated and interesting, and also, perhaps to your surprise, make evolutionary change faster and more powerful.

Thus the determination of eye colour is a networked effect of genes.  The evolution of life is a networked effect of the life-cycles of organisms.  Both at the smaller and meta scale – are networked effects.

However, we humans always seek explanatory frameworks to help us understand what is going on – to provide us with metaphorical anchor points of understanding.  The idea of the ‘selfish gene‘ is one such framework.  Adding a feminist perspective to the biology is another:

Feminist perspectives, however, such as those postulated by the Harvard scientist Evelyn Fox Keller, offer the potential to open new possibilities for interpreting the principles of life and are able to offer different perspectives on the nature of the organism.

Keller sought to rebel against the growing notion, prevelant around the time of the sequencing of the human genome, that genes allegedly controlled all aspects of development. Her contention was in regards to the central dogma of the gene, and argued that the popular notion of a discreet unit of biological ‘code’ did not exist in the way it was described. Keller proposed that complex networks made the decisions about what parts of the genetic code were actually expressed, not the ‘genes’, since DNA is unable to copy itself on its own without the cooperation of other molecules, which are under alternative, even more complex modes of instruction.

Which protein should a gene make, and under what circumstance? And how does it choose? In fact, it doesn’t. Responsibility for this decision lies elsewhere, in the complex regulatory dynamics of the cell as a whole. It is from these regulatory dynamics, and not from the gene itself, that the signal (or signals) determining the specific pattern in which the final transcript is to be formed actually comes.

I’m not proposing in this post to full explore the issues raised in the above essay – interesting though it is – I’d agree that the sub-text of the essay – that life is a complex network of interactions are all levels and pushing the idea of the primacy of one view (e.g. ‘organisms are machines’ or ‘genes are the primary engine of life’) by it’s attempted reduction, destroys the complexity that really exists.  While such frameworks do help us to understand and ‘trade in’ ideas, by the necessity of reducing them into a manageable chunk of transmittable data (a simple meme) – we cannot forget that underneath each simple framework lies a complex world:

Everything is fluid. Biology isn’t about fixed and rigidly invariant processes — it’s about squishy, dynamic, and interactive stuff making do.

Now do you see what’s wrong with the simplistic caricature of evolution at the top of this article? It’s superficial; it ignores the richness of real biology; it limits and constrains the potential of evolution unrealistically. The concept of evolution as a change in allele frequencies over time is one small part of the whole of evolutionary processes. You’ve got to include network theory and gene and environmental interactions to really understand the phenomena. And the cool thing is that all of these perspectives make evolution an even more powerful force.

(Also published on my blog.)

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