The evolutionary sidestep

EVOLUTION is full of surprises. I don't mean the funny-shaped animals, like flounder or angler fish, that readily evoke an exclamation or laugh. I'm referring to the improbable ways that evolution has of doing things, the surprising paths taken by evolution that violate all the stereotyped notions about progress. Sometimes evolution isn't the slow grind, meandering along, continuously editing random variations into ever-better versions.

Slow-but-sure is the popular image of Darwinism, but evolution really isn't very efficient. It's full of dead ends, which require backing up biologically in order to "make progress." Then there's coevolution, such as arms races. And, most surprising of all, biological evolution sometimes takes a sideways leap to tread a novel path.

Cultural evolution provides a shortcut (albeit a somewhat hazardous one) to appreciating similar features of biological evolution such as backing-up and sidesteps. For instance, in cultural evolution one can see:

* Temporary forms.- novel words introduced into the vocabulary - and their typical fate, though some survive several decades.

* New variations.- old products competing in the marketplace (breakfast cereals, soft drinks), many of them simple variations on a theme in search of a new niche.

* Replacement species.- old species of fasteners (anyone remember the diaper pin?) replaced with tape and velcro. "Baling wire and sealing wax" seem to have been replaced by battleship-gray duct tape.

* Vestigial features.- for example, those buttons on men's sleeves without matching buttonholes and those buttonholes on their lapels without matching buttons, carried over from an earlier age when they were functional, giving us some analogies to the appendix.

* Backing up.- as when the technology of ever-moresturdy adhesives was mellowed to create removable notepaper suitable for temporarily posting reminder messages on doors and telephones.

* Combinations.- an innovation successful for one reason may, in combination with another, prove handy for other (sometimes diametrically opposed) applications. My ancestor John Calvin imposed on sixteenth-century Geneva "a regimen which included getting up very early, working very hard, and always being concerned with good morals and good reading" (the emphasis on Bible-reading instead of sacraments promoted education regardlegs of birth or wealth). Though more fiercely anti-scientific than the Church of Rome (the scientist Servetus was burned at the stake in Geneva, in contrast to Galileo's house arrest), the Calvinist combination of equal educational opportunities and hard work turned out to be conducive to science in the following century, the Puritans becoming staunch supporters of science.

* Sidesteps.- The function of an innovation may drastically change after its initial adoption - computers invented for number-crunching becoming useful for noncalculating jobs (competing with typewriters and file cabinets, even running assembly lines and wristwatches), the old analgesics such as aspirin becoming useful for unexpected applications (such as preventing blood clots).

But, handy though cultural change may be for illustrating the themes of biological evolution, cultural analogies rapidly lead one astray when thinking about the mechanisms of biological evolution. It is downright hazardous to think of biological evolution using mechanistic analogies from cultural change, largely because biology doesn't pass on skills acquired during one's life to one's offspring.

One possible theme of evolution is "upwards to perfection." This concept was fashionable a century ago, fed by wishful thinking (how to make traditional religious notions "scientific"). But evolution seems full of dead ends. Most branches of the evolutionary tree of species die back.

Yet a closely related observation may, in fact, be true: organisms get fancier and fancier, capable of dealing with varied environments rather than just one. This seems to be a consequence of evolution being too slow to effectively "track" the frequent back-and-forth changes in climate - and so those variants which are capable of dealing with both old and new climates, with both old and new diets, with both old and new predators, are the ones which survive better. The classic example is intertidal animals, under daily waves of selection for their ability to tolerate both water and air habitats, and so eventually (about 450 million years ago) able to live on land full-time. Another way to accumulate mechanisms is through an arms race. When we discover that the black widow spider's venom contains a whole spectrum of toxins, a baker's dozen, capable of killing us by many different routes, we are glimpsing a bit of the spider's evolutionary history, of adding on additional armaments as a prey develops new defenses. From this, one learns to go looking at the spider's usual and accustomed prey (humans are merely thoughtless intruders, as when a camper forgets to shake out the shoe before inserting his foot) to see how they successfully defended against the first dozen toxins and so prompted the spider to evolve yet another toxin. Such examination of ancient arms races may allow us to mimic their successful defenses, by developing a vaccine or medicine. Backing up also tends to accumulate mechanisms: juvenilization has apparently played a major role in the evolution of humans from the apes, just as it did in the evolution of apes from Old World monkeys, just as it did in evolving the vertebrates from the invertebrates known as echinoderms. Backing up from overspecialization, then evolving some new specialization, backing up a bit from that (but keeping the specialized genes on reserve), and striking out in a new direction once more - we've done a lot of that, and at major turning points in our evolutionary history. The French have a phase, "reculer pour mieux sauter" ("Step back to leap better"), that epitomizes a crucial evolutionary principle.