Thursday, April 19, 2007

Accidental Irreducible Complexity

Suppose there is a primitive human settlement on the edge of a dense forest. The forest is very difficult to traverse, especially with equipment. However, the villagers need the fruits of the forest, so they create a pathway through the forest. Eventually, the pathway becomes a road that reaches the other side of the forest. One day, by chance, a villager uses the food trail to take some digging tools to the other side of the forest, where he digs for minerals. There, thanks to his tools, he finds an immensely valuable mineral. Soon, the forest road is used as much for mineral transport as for food. Finally, the village learns to plant nutritious crops in the flatlands near the village, and stops collecting low nutrition foods in the forest.

Now, look at the final state. The villagers are using the road only to transport minerals and tools for digging. Yet, if the road had not existed, they could never have transported the tools to make the initial discovery. It's just too improbable that the village folk would create a road to nowhere at massive expense, transport their equipment along this trail, dig, and find minerals. Since the villagers don't feed in the forest, and have forgotten that they did, this system is apparently irreducibly complex (IC). Not knowing this history, it appears that the villagers would have had to know about the minerals before they built the road and dug for them in the right spot.

By co-opting components of a system that serve alternate functions (nutrition, not just mining), one significantly reduces the improbability involved versus having all the components appear at once. You get the illusion of foresight.

And yet, intelligent design advocates like Behe and Dembski continue to deny that IC systems can evolve through incremental steps. This is willful blindness (or worse). Their claims have been thoroughly refuted, but they continue to make them.


geoffrobinson said...

A thorough refutation would involve actually showing the evolutionary pathway. You are describing a faith commitment to Darwinism. "There's this hypothetical village and there's co-option. I just know it."

Doctor Logic said...

Hi Geoff,

Behe's claim is not that we haven't found a detailed naturalistic explanation of the evolution of the flagellum. If that were his claim, I would congratulate him on stating the obvious. Behe's actual claim is that IC systems cannot evolve because the (small) probabilities are multiplicative. What has been shown is that, via co-option, the probabilities are not multiplicative. Hence, Behe's claim has been thoroughly refuted.

And it's not a matter of having a faith commitment to Darwinism. Neo-Darwinian evolution is a verified theory. It predicted common descent. Of the trillions of other possible topologies of descent, common descent is the one we observed after Darwin's prediction. So, we rationally conclude that life evolved through natural processes of variation and natural selection. This is not faith, it's reason.

Finally, I believe that biologists have discovered some instances of co-option in Behe's alleged IC systems. That doesn't mean we have found all of the co-option, nor that we understand the pathways in detail, but we know co-option happens in these systems. I hardly think it's a great leap of faith to suppose that a system that has several known co-opted pathways could be explained entirely by such co-option.

geoffrobinson said...

Everything I've read is a grasping at co-option, no proof of co-option. Darwinism as a belief system has become unfalsifiable in practice if not in theory.

geoffrobinson said...

"Behe's actual claim is that IC systems cannot evolve because the (small) probabilities are multiplicative."

More thought on this. The actual problem is that IC systems require complexity and simultanaeity, not just that they are multiplicative. If you have a step-by-step process and steps 1...(n-1) give no advantage, you can't appeal to a step-by-step process unless you drop the natural advantage.

It is more like a state diagram you would find in computer science than straight probabilities.

Doctor Logic said...


There's generally no physical reason why multiple mutations cannot happen at once. It's asynchronous and parallel. The reason why IC systems would not happen this way is that you need to have the right mutation or variations happen at the same time, not just any mutation or variation.

Suppose that an IC system needs three simultaneous mutations on three different chromosomes. Obviously, a chromosome could be mutated in many different ways, and the mutation is somewhat random (somewhat because some mutations are more likely than others).

So the analogy for this is three roulette tables that have to roll a 10, 20 and 30 respectively. Were we to relax the constraint for simultaneity, we would not be surprised that the numbers 10, 20 and 30 showed up on the respective tables during the course of a night. However, we would be very surprised to have them show up at the same time. The difference is that the probabilities are integrated when they can be achieved independently, and multiplicative when simultaneity is required.

Co-option eliminates the need for simultaneity. A mutation that shows up on the first chromosome sticks around because it has another use.