Monday, 6 September 2010

Evolving Complexity

One problem in a creationist understanding of evolution is the problem of gradients. Terms like irreducible complexity are part of the description of the general idea that it either works or it doesn't, framed with such questions like "what use is half an eye?" Where this line of reasoning fails is the distinction between having something and nothing at all, and improvements on having something.

To take the eye, for example, the creationist looks at the eye as it is now. Multiple interlocking parts, where removal or modification means severely-reduced function or even no function at all. The Darwinian is left seeming to defend the absurdity that the eye so intricately complex as being able to come about through random mutation.

While the creationist intuition that it either works or it doesn't is correct, what they fail to grasp is the historical contingency of the matter. That is to say the modern eye (no matter what species) is a product of gradual improvements on simpler working eyes, that the jump from no sight to sight was to the bare minimum that it could be. It's not from a bare patch of skin to the human eye, but to photosensitive cells. From there, the Darwinian process could improve on the eye, all the while having working sight but getting better and better over time.

This is the danger of the post hoc reasoning that creationists often employ. By looking back on structures with function that Darwinian evolution posits has been modified over millions of years then asking about intermediates from an ex nihilo state, the process is misrepresented and the creationist making the argument has inadvertently attacked a straw-man.

The end result is looking at structures like wings and asking how they came about as if the structure is useless unless it's a fully formed wing. In wing evolution, the Darwinian account posits that wings are modified limbs, which in turn were modified fins. Even if the creationist is willing to concede this account, it still posits an irreversible divide between the limb / wing distinction on the same grounds - either it flies or it doesn't and a modified limb ceases to be useful as a limb and as a wing.

In the case of the wing we can look to the animal kingdom to see such an intermediate: gliding. Many creatures independently have developed the ability to glide in some capacity. Yet even if we didn't know of an intermediate, it doesn't mean that it wasn't there. In cases like eyes or wings we do have a good ability to reconstruct an evolutionary history through many different converging lines of inquiry, so a case where there isn't an obvious intermediate isn't reason to abandon all that we know for the sake of an unexplained history.

The absurdity is actualised when this logic is used to justify anomaly-hunting; the search for the clinching evidence that conscious and intelligent input is at the heart of nature. Why else would structure on a bacteria matter for someone looking for a proof of God? It's just one more unexplained structure in the long battle of wanting the breakdown of the Darwinian algorithm.

Yet there are always going to be anomalies because our knowledge is incomplete. Perhaps some of those anomalies will be sufficient to modify or overthrow some scientific conceptions but finding an anomaly is never going to mean that all the times when the explanation does work can be discarded.

The problem would go away if properly applied to the Darwinian evolutionary algorithm. That the binary approach of either it works or it doesn't has to be the very first step in a cumulative process, not applied to structures that have been crafted cumulatively over millions of years. The eye either sees or it does not, but a fly eye and a human eye both see, as do the eyes of much more simple creatures.

To illustrate this concept, consider a synthetic material that no life-form has the ability to break down. This is an untapped resource. So a mutation in a particular bacteria comes along that allows for the bacteria to "feed" on this synthetic material. It doesn't matter how rudimentary this is, since it's able to do something no other organism has. Then subsequent mutations aren't about whether it can or can't break down this synthetic material, but how well it can. It could break down the material from the first valid mutation, all subsequent mutation thereafter builds on that.

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