Sunday, May 18, 2008

"Incredible" is not "impossible"

Let's get this straight once and for all: Evolution by natural selection is not a theory. It is a fact! Scientists are not slavishly attached to Darwinism because of some anti-religious prejudice or desire to evade God's moral law, as the fundamentalist preachers insist, but because it is a logical necessity.

Hear me out.

Consider any system, biological or artificial, that possesses three properties:

1. Entities reproduce from one generation to the next with inherited characteristics (eg.,physical, behavioral, or mathematical).

2. Variations of inherited characteristics sometimes occur (by mutation, sexual mixing, etc.).

3. Variations are acted on by some kind of selection (differential survival, sexual preference, computer algorithm, etc.).

If these three conditions prevail, evolution is not just possible, it is inevitable. Anyone who doubts that the three conditions apply to living organisms has not been paying attention or is willfully ignorant. Darwinian evolution is a logical necessity for life on Earth.

Whether evolution by variation and natural selection is sufficient to explain the full complexity of life on Earth remains an open question. Advocates of intelligent design think not, but they have yet to offer a single example of a biological feature that cannot in principle be accounted for by natural selection. Until they do, we need not take their religiously-motivated critique seriously.

One respected scientist who believes something beside natural selection is at work is Stuart Kauffman of the University of Calgary. His seminal 1993 book The Origins of Order questioned the prevailing opinion that natural selection is sufficient to explain "the overwhelming and beautiful order which graces the living world."

Kauffman set out to show that sources of self-organization exist throughout the natural world: The six-pointed snowflake and spherical raindrop are simple examples. In highly organized systems, such as biological organisms, these natural sources of order drive nature towards ever more complex forms, he maintains.

"None can doubt Darwin's main idea," Kauffman writes. "If we are to consider the implications of spontaneous order, we must certainly do so in the context of natural selection, since biology without it is unthinkable." But Darwin is not enough, he insists.

Life has not been cobbled together by natural selection acting on random mutations, he says. We are not Rube Goldberg machines slapped together piece by piece by evolution. Rather, life is "a natural expression of the stunning self-organization that abounds in very complex regulatory networks...Order, vast and generative, arises naturally."

In other words, we are more than the sum of our chemical parts. Life is an emergent phenomenon that arose when chemical systems on the early Earth increased beyond a "threshold of complexity." The subsequent history of life unfolds at least partly as a consequence of complexity.

Kauffman and his like-minded colleagues use powerful computers to explore how complex interconnected systems behave. They have demonstrated how complex arrays of simple elements can catalyze their own self-organization, and these computer simulations show intriguing parallels with the real-world history of life. If we can discover the laws of self-organization, says Kauffman, we will understand how our bodies developed from a single fertilized egg, and how our species emerged over billions of years from prebiotic chemicals.

He writes: "Almost 140 years after Darwin's seminal book, we do not understand the powers and limitations of natural selection, we do not know what kinds of complex systems can be assembled by an evolutionary process, and we do not even begin to understand how selection and self-organization work together to create the splendor of a summer afternoon in an Alpine meadow flooded with flowers, insects, worms, soil, other animals, and humans, making our worlds together."

Well, yes indeed. But fifteen years have passed since the publication of The Origins of Order and Kauffman and colleagues have yet to articulate the presumed laws of self-organization or support their necessity with empirical data. Frolicking in an alpine meadow is not enough. Meanwhile, the Darwinian paradigm continues to be the most fruitful template for biological research and marches from success to success. Random mutation and natural selection have even been used to design electronic circuits, including devices for which patents had been previously granted to human inventors.

Perhaps there is more going in the world of living creatures than the Darwinian paradigm supposes. I'm rather inclined to this view myself. But my intuition, or the intuition of someone as bright as Stuart Kauffman, does not constitute proof. Evolution by natural selection is a necessary characteristic of life as we understand it today. Whether it is a sufficient to explain the fullness of life remains to be seen. Those who think not have yet to make their case.

Further Reading

I have read Kauffman's The Origins of Order and At Home In the Universe. I have not yet read his new Reinventing the Sacred.

Discuss this essay and more over on the Science Musings Blog.