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Around the world, a few naturalists are conducting long-term observations of evolving populations of organisms in the wild: snails in Tahiti, fruitflies in Hawaii, finches in the Galapagos, and lake fish in Africa. Every year that these studies go on, there is a better chance that scientists can unequivocally demonstrate long-term evolution in action in the field. Shorter-term studies using bacteria, and recently flour beetles, show short-term evolution of organisms in the lab. So far, these experiments with populations of living creatures have matched the results expected from neodarwinian theory. The beaks of finches in the Galapagos really do thicken over time in response to drought-induced changes in their food supply, just as Darwin predicted.

These careful measurements prove that self-governing adaptation does spontaneously occur in nature. They also unequivocally demonstrate that noticeable change can emerge on its own by summing up the steady unnoticeable work of incremental deletions of the unfit. But the results do not show new levels of diversity, new kinds of creatures, or even new complexity emerging.

Despite a close watch, we have witnessed no new species emerge in the wild in recorded history. Also, most remarkably, we have seen no new animal species emerge in domestic breeding. That includes no new species of fruitflies in hundreds of millions of generations in fruitfly studies, where both soft and harsh pressures have been deliberately applied to the fly populations to induce speciation. And in computer life, where the term "species" does not yet have meaning, we see no cascading emergence of entirely new kinds of variety beyond an initial burst. In the wild, in breeding, and in artificial life, we see the emergence of variation. But by the absence of greater change, we also clearly see that the limits of variation appear to be narrowly bounded, and often bounded within species.

The standard explanation is that we are measuring a geological event in real time on a ridiculously infinitesimally small time span, so what do we expect? Life was bacterialike for billions of years before much happened. Patience, please! This is why Darwin and other biologists turned to the fossil record for proof of evolution. And although the fossil record indisputably exhibits Darwin's larger thesis -- that over time modification of form is accumulated in descendants -- the fossil record has not proved that this change is due solely or even primarily to natural selection.

No one has yet witnessed, in the fossil record, in real life, or in computer life, the exact transitional moments when natural selection pumps its complexity up to the next level. There is a suspicious barrier in the vicinity of species that either holds back this critical change or removes it from our sight.

Steven Jay Gould believes the exact transformation periods are removed from the sight of the fossil record by their incredibly instantaneous (evolutionarily speaking) mode. Whether his theory is correct or not, the evidence points to a natural limiting factor for extrapolated microchange that must somehow be overcome by evolution.

Synthetically reproduced protolife and artificial evolution in computers have already unearthed a growing body of nontrivial surprises. Yet artificial life suffers from the same malaise that afflicts its cousin, artificial intelligence. No artificial intelligence that I am aware of -- be it autonomous robot, learning machine, or massive cognition program -- has run more than 24 hours in succession. After a day, artificial intelligence stalls. Likewise, artificial life. Most runs of computational life fizzle out of novelty quickly. While the programs sometimes keep running, churning out minor variation, they ascend to no new levels of complexity or surprise after the first spurt (and that includes Tom Ray's world of Tierra). Perhaps given more time to run, they would. Yet, for whatever reason, computational life based on unadorned natural selection has not seen the miracle of open-ended evolution that its creators, and I, would love to see.

As the French evolutionist Pierre Grasse said, "Variation is one thing, evolution quite another; this cannot be emphasized strongly enough.... Mutations provide change, but not progress." So while natural selection may be responsible for microchange -- a trend in variations -- no one can say indisputably that it is responsible for macrochange -- the open-ended creation of an unexpected novel form and progress toward increasing complexity.

Many of the promises for artificial evolution foretold in this book will still come about if artificial evolution is merely adaptive microchange. Spontaneously directed variation and selection is an incredibly powerful problem solver. Natural selection indeed works over the immediate short term. We can use it to find what we can't see and fill in what we can't imagine. The question comes down to whether random variation and selection are sufficient alone to produce ever increasing novelty over the very long term. And if "natural selection is not enough" then what else might be at work in wild evolution, and what may we import into artificial evolution that will generate self-organizing complexity?

Most critics of natural selection concede that Darwin got "survival of the fittest" right. Natural selection primarily means the destruction of the unfit. Once fitness is created, natural selection is peerless for winnowing out the duds.

But creating something useful is the bugaboo. What the Darwinian perspective neglects is a plausible explanation for the origin of fitness. Where does fitness come from before it is selected? In the popular rendition of neodarwinism today, the origin of fitness is credited to random variation. Random variation within chromosomes produces a random variation in the developmental growth of the organism, which every now and then bestows increased fitness on the whole organism. Fitness is generated randomly.

As experiments in wild and artificial evolution have shown, this simple process can steer coordinated change over the short time. But given that natural selection weeds out all the uncountable failures, and that there is uncountable time, can random mutation generate the unbroken series of needed winners for selection to choose from? Darwinian theory has the sizable burden of proving that the negative, braking power of selective demise, coupled with the blind chaotic power of randomness, can produce the persistent, creative, positive drive toward more complexity we see sustained in nature over billions of years.

Postdarwinism suggests that other forces are at work in evolution in the long run. These lawful mechanisms of change reorganize life into new fitnesses. These unseen dynamics extend the Library in which natural selection may operate. This deepened evolution need not be any more mystical than natural selection is. Think of each dynamic-symbiosis, directed mutation, saltationism, self-organization -- as a mechanism that will foster evolutionary innovation over the long term in complement to Darwin's ruthless selection.