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Punctuated Equilibrium

Because Darwin's theory of evolution by natural selection is often misunderstood, it is not surprising that the theory of Punctuated Equilibrium, originated by Stephen Jay Gould and Niles Eldredge, which addresses a fine point in this theory, is even more likely to be misunderstood.

You may recall from comic books scenes where the hero's sidekick is exposed to an "evolution ray", and becomes a "man of the future", complete with bulging cranium. For reasons that, hopefully, will soon become apparent, if a ray were invented that made people smarter, it would have nothing to do with evolution.

People were able, over many years, to make poodles out of wolves by choosing which animals would be allowed to have offspring. Thus, artificial selection can produce modified creatures.

By putting together the well-known observations, which were commonplace even in his day, that:

Darwin proposed that animals are constantly being subjected to natural selection; the conditions of nature are constantly choosing which animals are allowed to breed. As they do so without the consistency a human breeder might apply, and without a conscious approach to a particular end result, they effect change more slowly than a human breeder would, but they do so in the end none the less.

Some misunderstandings of evolution result from not understanding the simple account of evolution given above. Evolution is the consequence of an environment imposing itself upon animals through dealing out death to them; it does not happen automatically, because of some impulse to progress within living things, by the mere passage of time.

But nothing in this simple picture, as stated above, would contradict the naive expectation that, due to natural selection, that perhaps a million years from now, nearly everyone would be both an athlete such as would today be in the highest ranks of international competition, and a scientific and mathematical genius as well. Perhaps the number of people who could play a musical instrument would also have increased slightly.

In fact, however, professionals in biology do not expect that this will happen. The earliest fossil remains of our species, those known as Cro-Magnon Man, show creatures likely to have been just as intelligent as ourselves, even though they didn't have as much interesting and useful technology available to be learned as we do. They were, if anything, more likely to be physically fit, and were rather stronger than most of us.

One way to explain this would be to claim that humans had "stopped evolving", since almost all of our children grow up to become adults, thanks to the effectiveness of human technology.

Although there is some truth to the idea that the lash of selection is lighter on humanity's back than upon most other creatures, the fossil record shows that the condition of not changing very much over time, referred to in the theory of punctuated equilibria as stasis, is very much the common condition of nearly all species. Including, for the duration of their existence, the species that became extinct, and were succeeded by species we consider to be more advanced.

Does the fossil record then prove that evolution didn't happen? Perhaps it might, if all the time that existed since the beginning of life on Earth was only just sufficient, through constant slow and gradual change, to bring about the complex forms of life that exist today. However, if being stuck in traffic for ten minutes can seem like a long time, and if a new breed of dog can be developed in less than a hundred years, perhaps evolution could still have taken place if a sizable fraction of the last three billion (thousand million) years had been "wasted", at least at first glance.

Because evolution doesn't work by magic, however, but by the action of the environment upon animals, one cannot argue for some intrinsic tendency of animals to evolve by fits and starts. The theory of punctuated equilibria must have, and does have, a different basis than this.

It rests on these facts:

Animals, if fortunate, quickly establish a modus vivendi with a new environment; once they have begun to flourish, natural selection tends to constrain them to remain with what works.

Because many of the misconceptions about evolution center around the relationship between evolution and the concept of progress, Dr. Gould has been at pains in his essays to disabuse readers of the notion that progress is a concept that relates directly to evolution. Adaptation to a particular environment, rather than another environment, is indeed not progress in an absolute sense. And mutations are random, much more often noticeably harmful than noticeably helpful, so they are not inherently progressive.

However, the popular mind is right about one thing. Any theory of evolution is a theory of progress. That is, it must be a theory that accounts for the observed phenomenon of progress, however much progress is judged by people in an imperfect and subjective manner.

For example, humans, with considerable justification of a kind, consider themselves evolution's most advanced product. But, while we are placental mammals, thus having a higher-energy metabolism than other kinds of creatures, and thus advanced in this sense as a steam engine is over a horse, or a nuclear reactor over a steam engine, primates are considered to be a primitive and generalized type of placental mammal; the ungulates, that is, animals like sheep and cows, are the most advanced and specialized mammals from a more objective perspective.

A human being, or a frog, is a far more complex and intricate item than a 35mm single-lens-reflex camera, or, to use the example given by Paley, a mechanical pocket-watch. A theory that cannot account for complexity and organization in creatures, but which can only account for why some have brown fur and others white, why some have thick, wooly fur, and others sparse, downy fur, would still require another agency to do the hard parts of designing the living creatures on Earth today.

The theory of punctuated equilibria was formed to address the appearance of the fossil record; not to account for progress, as the original theory of evolution by natural selection already did account for progress; those changes we regard as progress, because they are of general application in improving the chances of animals to survive in most environments, by making them stronger or swifter or more clever, would be selected for, at least in animals in certain types of demanding environmental niche. Other changes that we judge as retrogressive, however, are promoted in animals in other situations; animals lose organs they no longer use, so that they need to eat less food to sustain their bodies. Some parasitic animals are good illustrations of this; but even humans are not exempt from degenerative evolution, which is why it is harder for us to live on a meatless diet than it is for mice: we have lost the ability to synthesize some amino acids from others, thus, eight amino acids are essential for us, instead of five.

I can see two possibilities for the relationship between the theory of punctuated equilibria and progress in evolution:

I am quite sure the latter alternative is closer to the truth; but the possibility of the former alternative, if it is not dismissed, will cause objectors to claim that the theory of punctuated equilibria, even if true enough, is irrelevant to "real" evolution. And it is hard to dismiss the first alternative, or even name the alternatives, unless one is willing to talk about progress.

While the objective facts of science, and the processes that do, or do not, happen in nature, are not influenced by human cultural viewpoints, it is our own human attitudes that lead us to decide if a certain scientific theory answers the questions about which we ourselves are curious. When it comes to the development of life, naturally we are more curious about the causes of those changes in living creatures which we subjectively regard as having importance or significance.

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