William H. Calvin
UNIVERSITY OF WASHINGTON
SEATTLE, WASHINGTON 98195-1800 USA
This page is at http://WilliamCalvin.com/bk3/bk3day7.htm
|The River That Flows Uphill (Sierra Club Books 1987) is my river diary of a two-week whitewater trip through the bottom of the Grand Canyon, discussing everything from the Big Bang to the Big Brain. It became a bestseller in German translation in 1995.||AVAILABILITY limited; the US edition is now out of print. There are German and Dutch translations in print.
The River That Flows Uphill|
A Journey from the Big Bang
to the Big Brain
Copyright 1986 by William H. Calvin.
You may download this for personal reading but may not redistribute or archive without permission (exception: teachers should feel free to print out a chapter and photocopy it for students).
The idea is to start your sandal on the far side of the creek's channel at the top, so that the current will carry it away from the minihole below the little cascades. But sandal after sandal, cheered on by the spectators, falls prey to the hole, sailing around and around the eddy, getting pushed beneath the surface again when swept under the little waterfall. What those sandals need are miniature boatmen to steer them. Elves' Chasm is just down the way....
In a steady relay, boatmen run tirelessly from the bottom of the cascade, carrying their sandals back up to the top. Bets are placed, the racing sandals are urged on. The boatman with the biggest feet won. Like the baloney boats, his sandals were so long that they spanned the hole, continuing on through.
The Anasazi lived on top of Powell Plateau. Indeed, your chances of stumbling upon a ruin there are considerably higher than anywhere else around northern Arizona. Hundreds of people at a time must have lived there. Considering the resources (water was scarce, for example, once the snowbanks were exhausted) and the archaeologists' analysis of what the Anasazi left behind, they were probably seasonal visitors. Perhaps they came down to the river for the winter, as there was a whole collection of south-facing Anasazi ruins up behind Bass Camp last night. The situation certainly reminds me of Unkar Delta, right below those Anasazi ruins on the eastern side of the North Rim. "Going South for the Winter" may have been popular even a millennium ago.
There are quite a number of animal species living in the forest on Powell Plateau today -- deer, squirrels, chipmunks, rats, mice. To visit others of their species living on the North Rim proper, they would have to leave the woods and descend to the naked saddle, climbing back up 75 stories again on the other side. Because of this trek, the animals of Powell Plateau are largely isolated, inbreeding rather than mixing their genes with their neighbors across the way. Biologists love situations such as this. It seems to speed up the slow grind of evolutionary processes, producing new species from old.
This near-isolation happens in island chains all the time. An animal species will arrive on an island -- perhaps only a single pregnant female carried along by the winds or currents. Her progeny then populate the island and slowly spread to the other islands in the chain. Initially the animals on different islands can interbreed, though they will tend to breed among themselves. Pretty soon the collection of genes on one island may become sufficiently idiosyncratic that individuals from that island won't breed too successfully with individuals from other islands, even when given the chance. When the odds of successful interbreeding become low enough, a new species has effectively been formed.
Fruit flies (the same Drosophila that geneticists raise in milk bottles) arrived in the Hawaiian Islands long ago; indeed, the original island they inhabited has since sunk. Every remaining island has its own species of fruit fly -- indeed, because of all the ridges of lava that isolate the major drainages from one another, every major valley on each island is likely to have an endemic species of its very own. Now it is true that each valley has somewhat different vegetation, and the various species are to some extent specialists. That's the traditional Darwinian view of how new species spring up, that natural selection means only the variants that are best equipped to the valley's particular environment will survive, so that eventually each valley will have somewhat different-looking fruit flies from every other. But that isn't the whole story -- indeed, heresy triumphant, perhaps the least important aspect.
"Know the story about the squirrels on the North Rim?", Alan asked as he rowed us downriver. We were in one of those lazy spells on the river. "Those Kaibab squirrels look pretty much like the Abert squirrels over on the South Rim. They've got pointy ears, just like the cartoon characters. Both kinds build their nests pretty much alike. Sure seems likely that they used to all belong to one species. But then the river got in the way. Isolated them."
The river cut its path through the middle of the squirrel population, Ben asked? "Maybe," said Alan. "But then too, perhaps the squirrels moved up to the South Rim after the Canyon started forming. And some of the squirrels crossed the river. Had themselves a little population explosion, with no competition for all the squirrel food on the right bank. Probably happened a long time ago, maybe back when the river was dry, 4 million years ago. In any event, after all that time of being unable to mix their genes with the ones across the river, they probably couldn't interbreed now if they tried."
"We could always try and find out," volunteered Marsha. "I'll bet that Alan could catch a squirrel and take it across the river." Alan's raised eyebrows suggested that Marsha could catch her own squirrels. Marsha, however, is becoming irrepressible. The necklace has emboldened her.
Two populations may look identical, but be unable to interbreed because their gene pools have become too idiosyncratic. They are called sibling species. In other cases, two populations may look very different but still be able to interbreed. Such as German shepherds and miniature poodles -- both part of the single species, Canis familiaris. So appearances can be deceiving.
And experimental geneticists can create new species of fruit flies in the laboratory, with ease -- all without any selection. They just mimic what would happen in the island-hopping example. Select eight individuals from a cage (actually a little milk bottle), and put them in an empty bottle with plenty to eat. This is essentially what happens when a new island is invaded by a few individuals from the adjacent island -- a founder population. They will, as the phrase goes, breed like flies. Soon the empty bottle will be full of flies, all bearing some combination of the genes found in the eight founders. Now take eight of their offspring from that bottle and give them a new bottle, again mimicking another one-island hop further along the archipelago. Another population explosion occurs, all descendants of those the latter-day pioneers, who were in turn descendants of the original eight founders.
Keep up this bottleneck-and-boom sequence, mimicking the island-hopping that probably occurred as the Hawaiian-island chain was populated. Now, from the fourth such "island" bottle in the chain, take some individuals and see if they can interbreed with ones from the original bottle's population. You will find that the "inter-island" matings are nowhere as successful as "intra-island" matings. Some barriers to successful reproduction have appeared, not because of natural selection and adaptations (the bottles are such perfect environments that everyone lives), but just because of inbreeding followed by a population explosion, repeated a few times. With enough islands to hop, one is almost guaranteed a new species of fruit fly -- even without natural selection.
But why doesn't this speciation happen on the original island; why doesn't the original population fragment? Because they keep the gene pool stirred up, having far more choice in mates. On a secondary or tertiary island, one has to mate with someone who is a close relative, everyone sharing the same grandparents, etc. A sufficiently inbred population seems to lose its compatibility with the ancestor population, and that idiosyncrasy is speciation: reproductive isolation.
Of course, in real life, separate populations also become specialized, because natural selection is also involved in the process. The natural variability in offspring, caused by having sexual reproduction shuffling the chromosomes constantly, means that some will survive better than others in less-than-perfect environments. The islands with bananas will come to have fly populations which thrive better on bananas than do the islands without them. The invasion of the island chain by the immigrant species will thus give rise to a diversity of new species -- the new species may not have to look and act differently to achieve reproductive isolation, but in fact the less-than-perfect environments will select for physical characteristics such as wingspan, behavioral characteristics such as fear of predators.
"So you only find one species of fly on each island?", Marsha asked.
"At one time, but by now some of those new species on the out-islands have been blown back to the original island. If enough of them blow back, they'll interbreed with each other, even though they can no longer breed with the original parent population. So you'll end up having multiple species on each island." Alan paused, and decided to start rowing again. "The physical isolation isn't needed anymore to maintain the two different populations, once reproductive isolation also develops. Whenever you see two similar species living together, you know that they probably got started living apart."
And the squirrels on the two sides of our river provide a simple example of how another permanent barrier is erected between populations. There are inheritable variations, for example, in the month when the compulsion to mate strikes different squirrels. Some squirrels mate only during one day of the entire year. Alan noted that the Kaibab squirrels breed three months after the Abert squirrel's mating day, which is in early March. The later spring thaws on the North Rim eliminated those variant squirrels whose breeding seasons were normal by South Rim standards but which gave birth during the fatal North Rim snows. The North Rim survivors were those whose gene combinations happened to produce an extremely late breeding season -- usually a day in early June.
Selection and speciation -- there can be one without the other. Domestic dogs are a good example of selection without speciation (though achieved by artificial rather than natural selection). The ancestor of all dogs was a relative of the jackal. But by breeding the smaller offspring with each other, subpopulations were obtained. Both German shepherds and miniature poodles resulted as the body-size genes were segregated into subgroups. But they can still interbreed, since dogs don't speciate as easily as some animals (beetles will speciate if you look at them and frown). If the reproductive affairs of dogs were no longer controlled by humans, dogs would mix up those genes. Then most dogs would be mongrels, probably not unlike the original jackal-like dog.
So selection by the environment, whether natural or artificial, need not produce a permanent effect. Even if squirrels with heavier fur coats survived better on the North Rim, those heavier fur genes could easily be lost by subsequent mixing of the gene pool. Indeed, most natural selection is a fleeting thing, of no permanent significance. How, then, can the results of natural selection become permanently established?
The answer? Prevent remixing. Speciation is the cog on the ratchet. It prevents backsliding. A little change in the mating season, thanks to a difference in the month of the spring thaw, and presto -- you've got a new species, because the males and females of the different populations will never be interested in one another at the same time. And that will prevent adaptations such as better fur coats from being lost in a mixup of genes. A fur-coat ratchet, the delayed mating season serving as the cog that prevents backsliding to less hair.
"And here Marsha was all set to have me ferry a poor Kaibab squirrel across the river," Alan kidded. "Just think how unhappy a Kaibab would've been when mating season came and no one was interested. Such heartbreak!"
Marsha looks like she's plotting revenge on Alan, though. And Alan doesn't know about the necklace hoax.
The finches evolved in isolation. So did everything else on earth. With the finches, you can see how it happened. The Galapagos islands are near enough to the mainland that some strays could hazard there; they were far enough away that those strays could evolve in isolation from parent species. And the separate islands were near enough to each other for further dispersal, further isolation, and the eventual reassembling of distinct species. (In other words, finches blew to the Galapagos, blew to various islands, evolved into differing species, and blew back together again.)... It is as though an archipelago were an arpeggio, a rapid series of distinct but related notes. If the Galapagos had been one unified island, there would be one dull note, one super-dull finch.
.......ANNIE DILLARD, Teaching a Stone to Talk, 1982.
I'll bet that isn't what you thought sex was all about. Sex, however, isn't just a means of reproduction -- budding off, cloning, whatever, will take care of that. There are even virgin births in some otherwise sexual species where females do their own thing occasionally. Sex involves making a new individual that isn't quite like either parent.
That's what sex is all about? Added randomness producing more grist for the mills of natural selection and speciation? How disillusioning.
And the trail comes to another idyllic waterfall, tucked back into a narrow crack into which large boulders have become wedged. Greenery drapes down the waterfall, and the spray keeps finer greenery growing on adjacent walls. Elves' Chasm, it was called by someone who overrode the local fascination with Spanish and oriental names. You can swim to the grotto and then climb back up behind the waterfall, ascending up a level or two inside the rocks while getting a cold shower, and then jump off an elevated perch into the pool below.
There is a trail of sorts up the right side, with plenty of ledges for sunning available in the Tapeats, looking out over the view below. The trail leads higher up the valley to three more waterfalls. But before it leaves the chasm of the lower falls, there is a great overhanging ledge at one point on the trail, blocking the path like a giant flatiron. If you are elf-sized (and this is the only reason that I can see for the name), you can walk under this slab (ordinary mortals crawl). If you have the sticky fingers of a gecko, you can hug the rock and inch, spread-eagled, around the outside, exposed to the chasm. But somehow Gecko Chasm doesn't have the right ring to it.
Marsha is holding court down by the edge of the pool. Even sitting up above on the trail, I can hear the conversation perfectly. The bait has been taken -- just the suggestion of a code, from her question yesterday about Aztec bookkeeping, has gotten three scientists talking about what sort of message could be hidden in the necklace. And, the genetic code being the one they are most familiar with, it is not long until someone asks the obvious question: how many letters in the alphabet? Four different kinds of beads, it seems. And how many letters in the message? Twenty-one beads in all.
"Were there more beads -- is that a segment of a longer necklace?", asks Ben. Marsha reassures them that this was a complete necklace, according to the label on the museum display.
"So it could be a message 21 units long. Or maybe pairs of beads mean something?"
"No, that can't be right or there'd be an even number of beads. But triplets would work, seven of them giving 21. Triplets, just like the genetic code for proteins," explains Brian.
"See," Alan kids Marsha, "maybe you're carrying around the chemical formula for a deadly Indian arrowhead poison!"
Everyone laughs and began drifting away, several swimming to the base of the waterfall and climbing up inside it. Marsha waves at me, discreetly but triumphantly. She's really changed in the last few days on this trip; it's not so much that she feels safe flirting with the boatmen, but that she has a new-found confidence in judging other people correctly, in giving as good as she gets in repartee.
And then, remembering start codes and stop codes, Ben suggests that it might be a peptide of five amino acids instead.
Cam, who has come over and listened skeptically, points out that one could eliminate that possibility easily. If those first three beads were the standard start code AUG, then the last three would have to be a stop code. And, since all stop codes begin with U, the third bead from the end would have to be the same color as the second from the beginning.
How about that, it is! And the last two on the end are the same color as the first bead... hmmmm, the last three beads could be the stop code UAA. The four types of beads do match up in the right way at the far ends of the necklace. But that's ridiculous.
Brian is not to be deterred, pointing out that the remaining bead type must therefore be a C. They don't have our names for them -- Auburn, Unfinished, Gray, and Chocolate -- but they've named them with the letters from assuming that the first three beads, Auburn-Unfinished-Gray, must be AUG if they represent a start code. And that leaves the fourth type, what we called Chocolate.
Of course the last three beads could correspond with the starting beads just by chance. So it's a chance in a hundred that they match up. So what?
Everyone laughs again. What a funny coincidence! But the boatmen are starting to move people back down the canyon towards the boats.
Shortly after we get underway, the river takes a sharp right turn and heads due north, the third leg of our detour around the Powell Plateau. This long lovely stretch of river is known as Stephen Aisle. The Tapeats Sandstone is at river level in a number of places, with Precambrian rocks sticking through here and there. Some of these are thrust faults, four stories worth of uplift. At one point the shoreline Tapeats layers are thrust up several stories, then bent over and dropped vertically into the river, looking like a giant question mark laid on its side.
Heaven knows where on earth this spot was originally located back during the Precambrian, while it was being eroded, or during the Cambrian, when the sandstone was being laid atop it. The continents have moved around quite a lot since then. The story of continental drift and sea-floor spreading is one of the key scientific discoveries of all time, ranking up there with Darwinian natural selection as an all-important pervading influence on how life has developed.
Back to Hawaii. Granted that islands are handy for diversifying a migrant species, that the isolation is handy to speciating so that the effects of all the natural selection that takes place are maintained even when remixing occurs. But sea-floor spreading is what caused the Hawaiian islands to become a long string of volcanic islands in the first place. The volcanos that are currently active are all in the southeast corner of the southeast-to-northwest-tending chain. And now we know that the other islands used to be located where the active volcanos are now -- that they have moved northwest since then. The oldest remaining islands are the ones at the northwest end of the chain at Midway atoll, at 17.9 million years. The youngest island, dating only to the last half million years, is the big island of Hawaii. Where Kilauea and Mauna Loa still spew out enough lava to add many miles to the coastline every century.
It seems that there is a weak spot in the earth's crust underlying the drifting plate, so that magma can be pushed up to the surface. The active volcanos are currently sitting atop this weak spot. Thanks to sea-floor spreading to the southeast, the Pacific plate is slowly drifting northwest, no more than a hand's width per year. Periods of volcanic activity punch holes into the drifting plate overhead and push lava upwards to sit atop the surface -- a volcanic eruption. It is at first an undersea volcano, forming a seamount; then it breaks the surface and goes into business as an island -- and land plants, birds, and insects all manage to find it in short order, thanks to the wind and current. The island chain is like a giant paper-roll record of the volcanic activity of the last 18 million years.
In another million years there will be another Hawaiian island growing atop the hot spot. There are already growing seamounts beneath the Pacific Ocean southeast of the big island, submerged volcanos, islands in the making. The local joke has it that real estate promoters are already selling retirement lots on them. Of course the islands are sinking too, as the plate apparently cannot support all that weight from the lava; this downward bowing of the plate has created a deep trench around the islands, like a moat around a castle.
Thus the Hawaiian islands form a microcosm showcase for the processes of evolution everywhere. Even in the tropics, where making a living is relatively easy, the physical environment is constantly changing. Animals and plants have to adjust to islands sinking, with their mountains therefore catching less rainfall from the passing clouds. Volcanos periodically flood the landscape with new lava, so that a new round of natural selection operates during the ensuing centuries. New land will form on the margins of volcanos, opening up new opportunities for colonization. And the fact that the land is parceled out into a series of small islands rather than one long strip means that geographic isolation can work the ratchet in the gear wheels of evolution, conserving the creatures that variation and selection happen to produce.
Such forces have been operating on a world-wide scale for most of time, certainly since the land was first colonized nearly 400 million years ago. Life-forms never had the chance to rest, perfectly adapted to their environments, because the environment kept changing. The ocean currents, and therefore the continental weather patterns, were always slowly shifting. The fact that the plates are not firmly anchored has an overwhelming implication for evolution: it provides a constant drive to the evolutionary machinery, preventing a status quo from ever developing. Think for a moment of the unchanging moon if you want a contrast, what might have happened instead. It isn't just physical environment that is so important for evolution -- it is a constantly changing, yet not chaotic, physical environment. Most of the universe wouldn't qualify.
Arrogance comes in a variety of forms. The arrogance of great wealth, the arrogance of great power, the arrogance of great beauty, and the arrogance of a great master are bearable because they rest on an acknowledged and measurable base. The arrogance of ignorance, however, is unbearable because it is rooted in smug satisfaction with being isolated from the facts of the case. The anti-evolution plank in the platform of Christian fundamentalism is a classic example of the arrogance of know-nothings.SELECTION IS THE OTHER SIDE of the randomness coin. One doesn't do much good without the other. It is hard to appreciate just how powerful this combination is when the random variation is inheritable. People are always saying that our marvelous brains, or our precision eyes, are too complicated to have been designed by mere chance -- that surely their sophistication of design speaks to a guiding hand from above. It seems like common sense. But what we don't see are all the failures that chance also produced -- they're no longer around, those brains that got their owners into trouble before reproductive age, those eyes that didn't see the predator approaching. Selection usually brings with it a narrow, selective view of history.
......the biologist WILLIAM V. MAYER, 1984
This can be illustrated with a simple, presumably legal, get-rich-quick scheme (not my own invention; I seem to remember B.F. Skinner telling the story) which works because everyone's view of reality is partial, edited by circumstances. Suppose you send out a thousand postcards to people who gamble on the horse races, predicting that Pretty Boy will win the April race. Of course, you do exactly the same thing for Sunny Girl and the other eight horses in the race, except that you send each prediction to a different thousand bettors. After the race, no matter which horse wins, there are 1,000 bettors out of the original 10,000 who believe -- indeed know -- you predicted the race correctly. Forget the other 9,000 bettors who know you called it wrong. To those 1,000 who got the postcards correctly predicting that Sunny Girl would win in April, you try predicting the May race -- to 100 of them, you send postcards reminding them of your previous success and predicting that Naughty Nag will win in May. And do this for all the other nine horses on the May schedule as well. After the May race, there will be 100 people who'll know you've called two races in a row correctly.
To those 100, you now send a telegram offering them a chance to subscribe to your racing newsletter for a mere $100 per month. Don't make any claims about your methods or successes, just let them draw their own conclusions. They'll think you've got an inside track, because your record is so much better than mere chance (even those who calculate your one-in-a-hundred odds of being right by chance won't know about the other 9,900 postcards). And so (even after the expenses for all those postcards and telegrams) you'll have thousands of dollars in profit.
And so it is with judging evolution in hindsight -- we see the animals that survived, the organs that worked. The healthy babies we see born are those that survived the pressures for spontaneous abortion every day, from conception onward for nine long months. We seldom realize the editing that has gone on for thousands of generations. If one merely repeats the horse-race scheme for 10 races (generations), the probability of any one outcome is 1 in a billion; for 101 generations, it's one in a googol. A googol is a mathematician's term for a ridiculously large number, 10^100; there are, for example, only about 10^81 elementary particles in the universe. We've had 10^5 generations since the brain started enlarging, 100,000 opportunities for this selective view to compound itself.
Which goes to show why probabilities based on looking backwards are nonsense when many cycles of natural selection are involved; selection biases the results of evolution generation by generation, recycling the failures as food for another organism lower in the food chain, ratcheting the successes up from one stable state to the next. All it takes is sunlight to pump those probabilities -- and enough generations to discover the emergent stable states created by our environment. Natural selection is a mechanism, as R.A. Fisher used to say, for making common that which is highly unlikely. Evolution too buries its mistakes. Unlikely as we are, we're the survivors.
The next time someone laughs about monkeys typing Shakespeare, tell them that horse-race story -- and the trouble with thinking backwards.
Among all the events possible in the Universe the a priori probability of any particular one of them occurring is next to zero. Yet the Universe exists; particular events must occur in it, the probability of which (before the event) was infinitesimal... Destiny is written as and while, not before, it happens.
......JACQUES MONOD, Chance and Necessity, 1970
A depressingly large number of ... scientists with metaphysical proclivities [John Eccles, Karl Popper, Fred Hoyle, Francis Crick] have posed this problem [marveling over the thousands of coincidences necessary for life to exist].... To infer that super-intelligent beings are doing this on purpose [the so-called anthropic principle] is a strange reversion to the supernatural and proves not so much imagination as bankruptcy of imagination. The concept of life emerging as a natural, perhaps inevitable function of existence is too miraculous. We must have gods. What a shame we have such a lack of imagination.
......the science teacher RALPH ESTLING, 1983
Some variations in construction plan, produced by all that mutation and shuffling, are better than others for coping with the particular set of these factors we call the environment. They will be less likely to be weakened by pathogens or eaten by predators, more likely to be successful at locating food. And so they will produce more offspring. The particular genes that code for their version of body and brain will live on. The natural environment has, in essence, selected those genes that survive best -- hence the term "natural selection." This was the key discovery. Natural selection.
By itself this need not lead to more complex bodies and brains -- a new gene arrangement that simplified something might also be advantageous (greater energy efficiency, for example). But selection is never over. The next time the climate changes -- it might, for example, revert to the original weather pattern -- the altered environment will once again put each organism to the test. A more complex organism is more likely to be able to cope with several different environments. So while there is probably no upwards-to-complexity drive to variation and initial selection, there is a tendency for more complex multi-environment organisms to ride out the ensuing waves of selection better than the variations which were simply better suited for the first environmental change. In the long run, fancier lasts longer since versatility is a virtue. Lasting longer means more chances to mutate to a new species, more variants in the species competition. Ultimately, it is the fancier organisms that evolve -- a mere consequence of the simple interaction of variation, selection, and the constantly drifting environment.
The initial survival value of a favorable innovation is conservative, in that it renders possible the maintenance of a traditional way of life in the face of altered circumstances.
......ROMER'S RULE, as phrased by C.F. HOCKETT and R. ASCHER, 1964
General progress occurs in changes that are not only adaptive to single environments but also are prospectively more widely useful in other environments.
......the evolutionary theorist GEORGE GAYLORD SIMPSON, 1974
Selection, however, usually operates on how well something works (function), not on how it looks (morphology). Selection for function rewards one aspect of a morphological variant, while also hauling along any related anatomy at no extra charge, "for free." For example, variations in the time of sexual maturity result in some adults being more childlike than others, their development truncated. If juvenile playfulness were rewarded by selection (because, say, juveniles were more likely to try out new foods than traditional adults), and the successful adults were those who remained more juvenile, other anatomical changes would occur without themselves being exposed to selection (for example, the flatter face of juvenile primates, their smaller teeth, their larger brains compared to body size). Cause and effect are often so indirect in biological evolution as to completely obscure the reason why a useful variant arises.
Thus, natural selection may produce adaptation to an environment in terms of one function but, in passing, change another subtly-linked anatomical feature. And so the path of evolution meanders, like this river (though, now that I look, this is one of the straightest stretches of river I've ever seen -- we must be following an old fault line).
And sometimes we see a sidestep in evolution, where a structure under selection because of one function becomes secondarily useful for a novel function, as in the thermoregulation-to-flight story of feathers. As Darwin said, "In considering transitions of organs, it is so important to bear in mind the probability of conversion from one function to another."
Are there trends to evolution, principles that would predict us as an inevitable product of the evolutionary machinations? Nineteenth century naturalists were fond of the notion of orthogenesis, saying there was a straight-line tendency to evolutionary paths that was independent of natural selection (for example, a predetermined "upwards to perfection" tendency). While that isn't believed anymore, there are several tendencies that are thought to operate. One is the aforementioned tendency towards multienvironment organisms ("complexity"). A second is a tendency to speciate, the reproductive isolation thus preserving the editing done by natural selection from subsequent dilution. A third is some tendency toward increased size; the punctuated-equilibrium theorists note that shell size may creep upward during the otherwise static period of 3- to 10-million years that a single marine molluscan species exists. These three mundane trends lack the appeal of "perfection" as a principle, but they do explain a lot. I wouldn't be surprised if there were additional, yet to be discovered, mundane principles to add to this list but to postulate cosmic goals is to simply short-circuit the discussion.
The otherwise wandering and opportunistic path of evolutionary success leads to all sorts of Rube Goldberg arrangements in nature, the roundabout designs loved by cartoonists that any reasonable Creator would have thrown in the wastebasket. There is, for example, the mixed up wiring of the brain, where the nerves from the right side of the body cross to the left side somewhere in the spinal cord or brainstem, and go to the left cerebral cortex. Our right hand movement commands start from the left cortex and then cross over to the right side in the brainstem, finally exiting to go to muscles on the right side of the body. How did this mixup get started?
Dan Hartline points out that to escape a threatening stimulus to one side of the body, a fish has to contract the muscles on the opposite side of its body in order to flip out of the way of harm. Thus, sensory nerves have to connect to the muscles on the opposite side of the body. And we're a late-model fish -- our fancier wiring is superimposed on the more elementary wiring that is crisscrossed, for the purpose of escaping from predators.
My favorite example of meandering design, however, is the sequence of preliminary forms that a mammal goes through before attaining the familiar adult form -- what gets called prenatal and postnatal development, or ontogeny. Just imagine constructing a digital computer by first setting out to build fingers to count on, then switching to an abacus, then changing your mind again, backing up a few steps and scraping the abacus beads, taking off in a new direction to build a mechanical calculator, scrapping it for a Jaccard programmable loom, then superimposing an electrical design based on vacuum tubes, pulling the tubes and replacing them with transistors, scrapping them for integrated-circuit chips even before all the tubes have been replaced, and so on. And going through this nonsense each and every time you wanted to build an additional computer.
Yet to construct a human brain and its attached body (which, someone quipped, is still the only general-purpose computer that can be made by the unskilled labor of two workers), one cell divides into a collection of cells that looks something like an invertebrate called an ascidian. It then changes course to head in the direction of a shark's elongated body form, but shifts toward a proper fish's specializations such as gills, then scraps the gills after a few weeks and remakes the body into the image of a reptile, then into that of a primitive mammal, then realigns things into the primate ape format, and finally, with some fine tuning of the relative growth rates, grows the big brain of the human form.
The possibility has to cross your mind: Maybe the cell's DNA doesn't know any other way to make a brain. It's like a treasure hunt, with new instructions opened at each stage of the game, telling the developing organism where to go next in words that can only be interpreted in the context of its present position. Instructions, overlain by modification after modification. An architect would scathingly dismiss it as "design by change-order." But I think it is rather nice to evoke your ancestors, to bring them to life ever so slightly, each time you make a baby.
The large brain, like large government, may not be able to do simple things in a simple way.
.....the physiological psychologist and brain theorist DONALD O. HEBB, 1958
This would make an excellent camp for the night, but we're going down to an even better one, Blacktail Canyon, in just another two miles. It's not known so much for blacktail deer as for a spectacular canyon of corrugated Tapeats sandstone leading back up to Powell Plateau.
Our Rube Goldberg story has been spreading to the people on the other boats, and so our little shade-loving group has been talking about making babies.
"You mean that the baby looks like a shark at one stage? And then an ape?", exclaimed Abby.
"Well, it has gill slits at one stage, a few weeks into gestation. They disappear in a few more weeks," explained Rosalie. "But you don't see what look like familiar adult animals. They're really more like fetal versions of those animals. And even that isn't quite true, because the evolutionary changes have been made merely by varying the growth rates of different parts of the body."
"Maybe the head grows a little faster than the body," I interjected, "and therefore winds up bigger when it is finished. Different rates, just like thermostats."
"Sure, just take a look at that little sandwich of two metals inside any wall thermostat, sealed together. Both expand when heated, but one expands faster than the other. Since they're glued firmly together, this means that the straight strip of metal begins curving sideways. And trips the furnace switch at some temperature."
"But babies aren't metal."
"No, but the baby has lots of curved surfaces, and they form in exactly the same way," Rosalie resumed. "Two sheets of cells, one of which grows faster than the other, and the surface curves into all sorts of shapes. And there are master clocks too, which set the overall time schedule of development. They cause monkeys to become adult in three or four years. In apes, they're slowed down so it takes eight years. In us, they're slowed down even more."
"It takes longer to make us because we're fancier?", asked Ben.
"No, there's no real reason why it takes nine months rather than the monkey's four months, except this evolutionary history, everything getting slowed down by half at each transition. It only takes a month to make one of the local squirrels -- that's the time between the mating day and birth," added Rosalie.
"It isn't just time to grow, you know," I said. "It's also the time it takes for some cells to die and be removed. Not all of development is growth, where cells are added and the fetus gets bigger. Quite a lot of development is carving, removing parts selectively via the death of cells. Just as in the computer story, where the abacus is scrapped, the body is sculpted by development."
"I read somewhere that adults lose 10,000 brain cells every day," said Abby. "Is that true? Am I degenerating?"
"Not that we've noticed," said Rosalie, smiling. "All that cell death seemed ominous back when we didn't understand that development was accomplished by both growth and sculpturing. That daily loss of brain cells started way back before birth. And development's never over -- it doesn't just stop when you become adult. That's why you're losing cells today."
"Mind you," I explained, "we don't understand what the adult cell death is in aid of, but I suspect that it's refinement of structures. Brain cells start out by making lots and lots of ties to other cells, but then some of the connections are broken. When a rat is born, many regions of its brain make connections to its spinal cord. But months later, only a few regions have remaining connections to the spinal cord. The different parts of the brain aren't anywhere as well defined early on as they later become -- and a lot of that finer detailing comes from connections being withdrawn, from cells simply dying."
"So what determines if a cell dies?", asked Ben.
"Some of it seems to be good old Darwinian selection," answered Rosalie, "on a small scale. Overproduction, then editing. Take, for example, the spinal cord cells that command the muscles to twitch. At first, there are more of them than there are muscle fibers for them to operate. They send out little thread-like axons to make contact with the muscle fibers. But once a muscle fiber has a connection, it'll reject other axons that approach it. Some spinal cord cells wind up without a muscle fiber to operate. They're likely to die. Mini-Darwinism?"
"And one of the Rube Goldberg aspects," I picked up, "is that whole muscles are created, then killed off. And many of the spinal cord cells that run the temporary muscle also die."
"I just can't get over the cells dying right and left," said Abby, shaking her head. "Just as I can't get used to the idea that half -- or is it four-fifths? -- of all fetuses spontaneously abort."
"Welcome to the club," said Rosalie. "It was a shock to me too, but I think the problem is that we try to trace ourselves back to our individual beginnings. And think that it's a miniature of ourselves, fully determined. Thinking backwards gets us into trouble. That zygote or fetus was no more me than a cell of my skin, scraped off by the boat this afternoon, whose nucleus contained the same genetic information. That skin cell could, in theory, have been cloned to produce a duplicate of how I was at conception. But inevitably it'd grow up very differently than I did, make different decisions than I did, and its whole personality would wind up somewhat different, even if it did have red hair and look like my twin. Worrying about fetuses that could potentially grow up is like worrying about the lost opportunities to make a baby with each menstrual period, each of those unique, never-to-be-repeated ova down the tube. A fetus that grows up into a baby, and from a baby into a real person, has had a lot more invested in it by the parents and society -- it's far more than just the genes it started with."
"That beginning fetus is just the foundation onto which all the rest has been added," I said. "If nature makes more foundations than the ecological market can ever bear, that's because nature's method of building is different than when we build a house. We don't start three foundations but then finish only one of them. Nature does."
Rosalie turned to Abby. "Just imagine clearing a lot for a house every month -- but usually nothing else happens and the weeds grow back in weeks. But some months, the lumber is actually delivered just after clearing has taken place, and construction starts. Still, most starts are scrapped, maybe because the carpenters and the plumbers got their schedules tangled up. And so it's all cleared away and the weeds come back -- that seems to be easier than untangling the snafu. Only some of the starts are actually carried through to be finished houses, completely furnished. Now at what stage are you going to call that building-in-progress a 'home'? Sure, each cozy home was once only a foundation, but we wouldn't call that collection of lumber and nails a home, would we? I wouldn't even call it home on the day that the builder finished it and delivered the house to its new owners. It's a home only after it's furnished and lived in."
"And all that elective abortions have done," I added, "those abortions that all the fuss is about, is to make it 25 foundations that are finished for every hundred started, rather than maybe 33. In the good old days, malnutrition probably changed the odds even more than that, maybe only 15 finishing for every hundred starting. All we ever see are the ones that finish. It's a very selective view of reality. Beware of thinking backwards."
There is probably a constant pressure to spontaneously abort, which only a particularly successful fetus can overcome by sending enough of some sort of "I'm okay, mom" signals. Mothers that didn't have such an abortion mechanism would repeatedly waste nine months on nonviable fetuses, rather than being able to try anew after several months and so be able to squeeze many more tries into her reproductive years. As in the horse race prediction scheme, we only see the winners. The unsuccessful exist briefly, but we are simply unaware of them.
Thus abortion seems to be quite natural, editing out the more pernicious combinations of genes; indeed, much natural selection may take place in the womb, unobserved. These natural abortions are not, however, the first stage at which natural selection acts. There is the great sperm race, an obstacle course of mammoth proportions. And at the end of it, one may see an ovum sitting there, sometimes surrounded by hundreds of sperm trying to gain admittance through its outer membrane, the ovum somehow deciding which one to admit.
One is a line of selection wholly different from the usual one. Sexual selection is the name that Darwin gave to an effect which seemed to differ from the "natural selection" exerted by such elements of the environment as the availability of food, predators, disease, and so forth. Sexual selection usually evokes a vision of competition between males for access to females, though there are examples of females selecting for males in those species in which the males perform a lot of the infant care that greatly increase the chances of offspring survival. Certainly females tend to select males that look healthier, which shows how two supposedly separate things, sexual selection and natural selection, can get all mixed up (sexual selection involves the appearance of fitness, not its actuality -- advertising versus performance). While the usual examples of sexual selection involve the development of bright colors and strange courtship displays among the birds, one can see it right down at the level of the sperm surrounding the unfertilized ovum, banging at the gates.
The sperm does, of course, have a long way to go before getting there, what with the obstacle course created by courtship, the long passage through a hostile chemical environment from vagina to uterus to the Fallopian tubes where the fertilization actually takes place. But hundreds make it. So whose sperm are admitted? Sometimes it is simply a matter of sheer numbers. Relative numbers, that is (in absolute numbers, sperm production is absolutely profligate; in three weeks, one human male produces enough sperm, given the perfect delivery system and indiscriminate ova, to impregnate every woman on Earth).
In many types of animals that do not compete for mates, where all males get a chance to mate with a female in heat (male chimpanzees will actually stand in line behind a receptive female, waiting their turn -- the queue itself could be a product of sexual selection!), relative numbers can be important. A male producing only 4 million sperm a day rather than his neighbor's 40 million will stand, everything else being equal, only one-tenth the chance of having one of his sperm be the lucky one. That mating system is literally a lottery, where one's chances of winning depend on how many tickets one can afford to buy. Monkey and ape species with such multi-male mating systems may gradually develop an arms race in testis size, as variants with copious sperm production will tend to be more successful. The woolly spider monkeys of Brazil have baseball-sized testicles as a result, and chimpanzees are not far behind, with testes three times the size of a gorilla's even though their bodies are only one-fourth as heavy. That's sexual selection.
Another common result of sexual selection is that males may be larger than females. This may come about because, at some time in the history of the species or its ancestors, the mating system involved competition between males for access to females. The bigger males likely won the competition, on the average, and thus propagated their genes on the Y chromosome for making extra testosterone, that male hormone having quite an influence on muscle growth. Gorillas have a harem type of mating system, and the males may be twice as large as the females, reflecting generation after generation of male competition for the proprietorship of a harem.
Besides all this competition for getting sperm up to the courtyard of the ovum, selection may also occur in the final act of fertilization itself. As indicated by the microscope picture of a meditating ovum surrounded by hundreds of anxious sperm, fertilization is not like shooting an arrow into a ripe melon. Some sperm may be more "acceptable" to the ovum than others, once their surfaces have been tasted for recognition signals. Should the sperm and the ovum both possess the same genes for controlling the immune system (the genome's major histocompatibility complex, or MHC), the sperm will probably be rejected. This promotes variety, since successful fertilizations yield an offspring that has two different versions of the MHC, and thus more strategies from which to choose later in defending against invading organisms ("heterozygous for the MHC" is what it's called in biology, "homozygous" meaning identical copies of the gene).
Thus the ovum is something like a suspicious shopper sniffing all the produce offered her by anxious merchants who have just finished running a marathon -- then she decides, with a great thunderclap that seals the deal. That's the way it can sound if you've hooked up a wire from the ovum to a hi-fi system -- the electrical signal announces the acceptance of one sperm and seals the ovum's membrane against further penetration by additional sperm. It's the first use of electrical signals by the new individual -- they're subsequently used to contract muscle, warn of predators, secrete saliva, and even think great thoughts.
Both testicle size and sexual dimorphism are, in these examples, mere side-effects of the disproportionality in the numbers of male sperm and female pregnancies, shaped in turn by the particular mating system in use. These size excesses are not produced by the environment, in the manner of natural selection. Sexual selection could become maladaptive. Adult male mountain gorillas can no longer take to the trees -- they are simply too heavy, though the females and juveniles can still use trees as a refuge. Just another interaction between sexual selection and natural selection that blurs the boundary.
It's one more example of the lack of planning, of many different random plans being tried out and let run for as long as they can. It's no way to run a railroad -- no foresight, no planning ahead. But it works, given enough time and the right conditions. And it just may be the only way in which the universe has been run, up until now.
In recent years, genes have even been snipped out of a chromosome with restriction enzymes, then spliced into the DNA of a bacterium. In this manner, one can fool the bacterium's cellular machinery into producing a new product that is coded for by the excised DNA strand. Thanks to the fact that we shared a common ancestor with the bacteria billions of years ago, we both still speak the same internal language of protein manufacture, the same genetic code. Human insulin and human growth hormone are two things that have been produced by bacteria in this manner, to the great relief of those people who do not produce enough of their own.
Some people say that genetic engineering "isn't natural," that it is fiddling around with nature. In one sense it is only doing what nature itself is always doing each time that crossing-over occurs, every time selection shapes up a new population, each time that geographic isolation runs the speciation ratchet that conserves new traits. We help that along every time we swat a fly, thus helping to breed smarter and faster flies for tomorrow. Genetic engineering is just faster, much faster.
Of course, some changes in speed can become important changes in kind; rockets were a big step over slingshots, especially when we managed to sling a spacecraft called Pioneer all the way out of the solar system, never to return. To create something that will probably outlive the death of our Sun a few billion more years down the line -- that's a human accomplishment of immemorial proportions, not just a little improvement in speed.
Our whole civilization is one of those changes in kind, not just the genetic-engineering aspect of it. The dangers of genetic engineering are very much those of our whole farming and pharmaceutical industries: namely, that we don't know what will happen down the road as the new pesticides and drugs perturb the system, because our culture is still so ignorant of ecology, of how the elements of the environment hang together and buffer one another. We do know that the natural ecosystems cannot absorb some insults forever. Unless we somehow limit our pollution and our population growth, the earth may fall apart on us as we ruin one carefully-wrought ecosystem after another.
Evolution, of course, is the vehicle of intricacy. The stability of simple forms is the sturdy base from which more complex stable forms might arise, forming in turn more complex forms, and so on. The stratified nature of the stability, like a house built upon rock on rock on rock, performs, in Jacob Bronowski's terms, as the "ratchet" that prevents the whole shebang from "slipping back."Conquistador Aisle looking downriver from Mile 120, from Leonard Thurman's Grand Canyon River Running web pages.
......ANNIE DILLARD, Pilgrim at Tinker Creek, 1974
The floor of the canyon rises in a little series of steps, forming what can only be called bathtubs -- modest-sized depressions in the floor filled with water from the slow-flowing creek. But sculpted when the water was thundering down: standing waves cut these little bathtubs for us.
Soaking tubs! But no soap is allowed, not in any side creek, as they are fragile ecosystems. And the water, while not as cold as the river, is not exactly warm. The sun penetrates this narrow canyon only at midday. The bathing, however, is going on in a big way back at the river, as we discover upon our return to camp. It has become a tradition of the late afternoon.
Ben first asked Cam if he remembered the amino acid that was encoded by the GGG nucleotide triplet. "Ah, must be glycine," said Cam.
What about UUU? Cam was uncertain, and called Brian over. He remembered that UUU was phenylalanine. And what about CUU? Neither Cam nor Brian could remember the genetic-code table that well, so together they all went in search of an expert.
After drawing two blanks, they asked Jackie about CUU. "Leucine," she said, "definitely leucine. Why do you want to know?"
"Just a little test," said Cam hurriedly before the others could open their mouths. "We're just playing a little game. Do you remember UAU as well?"
"Sure," said Jackie, "that's tyrosine. What do I win?"
Ben was scribbling it all down, and the others were looking over his shoulder. Taking the sequence AUG-UAU-GGG-GGG-UUU-CUU-UAA, he now had written "(start)-tyrosine-glycine-glycine-phenylalanine-leucine-(stop)."
He shook his head, then showed the list to Jackie. "Does this amino acid sequence make any sense? I mean, is it nonsense or a real peptide?"
"Let me see. Sure, it's enkephalin," replied Jackie cheerfully, "it's leucine enkephalin. What ever is this game you're playing, anyway?"
"You mean it's a real hormone?" exclaimed Ben, doubt setting in.
"Of course it's a real peptide hormone, you idiot. It's also a part of the longer chain of beta-endorphin. That's a classy sequence of amino acids you've got there," explained Jackie, warming to her subject. "Stops pain, supposedly makes you feel good. You've probably got a lot of it on the brain right now, after romping around in all that cold water at the beach. Good old enkephalin, good for what ails you. What does ail you, anyway? You look a little green around the gills. What's this all about?"
Ben sat down. "I think maybe I've been out in the sun too long."
Cam and Brian looked sheepish as Jackie turned toward them with raised eyebrows, waiting for an explanation.
"So where did you get that paper with the letters on it?", she demanded of the mute trio. "Manna from heaven? Old homework papers stuffed in your jacket pockets? Something from a fortune cookie?"
"Okay, Cam," said Ben, ignoring the question, "so you calculate the odds of this happening by chance. Now it isn't just the three beads at each end being consistent with the start and stop codes. It's twenty-one beads of four types, all in the right order for an important natural substance. What's the chances of that being random?"
Cam looked up to heaven. "I can't count that high."
"Beads?" interjected Jackie. "Whatever are you talking about?"
"Marsha's necklace," replied Brian at last.
"Well, what about it?"
"Marsha's necklace spells out leucine enkephalin. That's all." Brian was looking at the ground as he spoke.
"An alphabet necklace? How clever. Just like an anatomy T-shirt."
"You don't understand," said Cam miserably. "This is Marsha's Indian necklace."
"Are the Indian reservations making anatomy T-shirts too? They've branched out from pottery and silver jewelry? Getting the university bookstores to sell molecular biology necklaces? So what's the problem?"
Cam stood up and looked around for Marsha.
The trio hauled Jackie along with them as they went in search of Marsha. She was down at the water's edge, flirting with the boatmen, giving Alan a hard time as he fished beverage cans out of the bilges.
"Marsha," began Ben, "could you show Jackie your necklace?"
"Sure. Did you figure out how many bushels of corn the poor people had to pay in taxes?"
Ben held up one finger, asking her to wait a minute, and turned to Jackie. "Marsha copied the necklace from the museum at Mesa Verde. And thought that it might be like those Aztec knotted strings that were used for keeping tax records."
Jackie took off her sunglasses and looked closely at the necklace. "I see. There really are four different types of beads."
"Now look over here at the beginning," Cam pointed. "If you assume that those first three beads are the start code, AUG, then this other dark type of bead must be C. What got us interested is that assigning AUG to the first three types suggests that these last three beads are UAA, which is a stop code. And there are exactly 21 beads, seven triplets worth. Just as if this were a string of messenger RNA, all that's needed to tell the ribosomes how to make a five-part peptide."
"And if you work through the rest of the beads, you get this list I wrote down on the paper," exclaimed Ben. "Here, you check to see if I copied them down right."
Jackie took the paper and began working through the necklace. "Well, I suppose this bead could either be a C or an A -- it's sort of dirty and ambiguous. But you're essentially correct. These three would be the start code, then tyrosine, glycine, glycine, phenylalanine, leucine, and a stop code." She shook her head, disbelief finally setting in. "That is truly amazing."
The boatmen came over to inspect the necklace, demanded an explanation of what everyone was so excited about. So Ben explained the genetic code to them. And what the necklace seemed to be spelling out -- the genetic code for how to make enkephalin, the powerful pain-killing hormone which the brain itself produces. Supposedly, in some people, producing euphoria just like morphine.
Jackie and the trio are feeling very pleased with themselves for solving the puzzle, even though they still didn't know what to make of it.
"Boy, dip your arrowhead in that stuff, and your prey would sure die happy," Alan observed. "You really think they did that?"
"But it's absurd!" exclaimed Cam. "How old did you say that necklace is, the one you copied the pattern from?"
Marsha, looking as astounded as the rest, replied that it was at least a thousand years old, according to the museum's sign. She held out the necklace so that she could look down and see it, her eyes wide. Not only does that girl have stage presence, but she can improvise too. She denied any knowledge of the genetic code herself, deflecting suspicion. But she hyped the discussion a little, suggesting that it would have made a great necklace for an Anasazi medicine man to wave over his patient around as a symbolic pain-killer.
Thanks to all the loud exclamations, a crowd had gathered around Marsha and her necklace, Rosalie among them. They too wanted the mystery explained to them. Soon everyone was saying how amazing it is -- or how absurd it is, that nothing that old could be that scientifically advanced. After all, enkephalin wasn't even sequenced until the 1970s. How could the Anasazi have known about it?
The reaction went in waves. First came the astonishment that the trio, with Jackie's help, had figured out that the necklace was a code. And then broke the code. With the secret message being no less than enkephalin. Then came the rejection of the notion that the Anasazi could have known about it a thousand years ago. Impossible!
"Now I'll bet that's just what some astronomer said," teased Rosalie, "when they showed that Fajada Butte over in Chaco Canyon was a fancy device for tracking the 19-year cycles of the moon. If the Anasazi were that sophisticated in astronomy so long before we discovered such cycles, maybe they were sophisticated in other areas too. Just think how the Indians domesticated corn. Maybe they knew more than just practical genetics?"
The bait caused some discussion between neighbors. And much head-shaking. Someone started to explain how big the 20 corn chromosomes were, how different types of corn hybridized. More beer cans popped open. After all, the enkephalin molecule is about the same in the octopus as in us. That probably means that enkephalin has been around since the Cambrian; is half a billion years old. It isn't as if it has been around only since the 1970s, when its sequence was determined and some of its functions discovered. Still.... Impossible.
Entering into the spirit of things, I reminded them of Peter Medawar's dictum, that scientists treat a new idea the same way that the body treats a foreign substance: it is rejected.
They tried to stretch their credulity. And they were most intrigued -- after all, usually when you hear "Impossible!" uttered with delight, it's a sign of a scientific problem posed critically, possibly about ready to crack. And it attracts scientists like flies. But no one took enough of the bait to emerge as a champion of ancient Anasazi molecular biology. Several people did, however, sound determined to stop by Mesa Verde on the way home, to check out this necklace for themselves.
"But that Chaco Canyon observatory is a feat of naked-eye astronomy," replied Jackie finally, addressing herself to Rosalie, "and this is more as if those Fajada slabs had all pointed, not to the sun and moon, but to the black holes known only from radio astronomy." The more excited Jackie gets, the faster she talks. "Have the archaeologists dug up any Anasazi microscopes lately? Or chromatographs? Or written records of chemical formulas? This isn't just kitchen chemistry that's required, you know. There's simply got to be some other explanation for this necklace."
Silence. Then more head-shaking. Finally, Ben stood up and bounced onto the bow of the boat in a perfect imitation of the boatmens' loose style, causing a low booming sound as he balanced himself, arms outstretched. Having gotten everyone's attention, he solemnly raised his beer can in a toast to Marsha, cocked an inquiring eye at Rosalie, and mused aloud: "Piltdown, Piltdown, wherefore art thou, Piltdown?"
Marsha and Rosalie could keep straight faces no longer, and collapsed in each other's arms. Soon everyone was laughing as the truth dawned.
There are nautiloids just downstream from the campsite, and we've been over to see the fossils in the fading light. I took a canteen of water and, with the aid of the light from a flashlight nearly parallel to the surface, we were able to see the chambered forms. There is no way to estimate how intelligent they were, there being no bony braincase as for hominids. If they were particularly omnivorous, perhaps they were as smart as their living cousin, the octopus. As clever as dogs and ravens. We last shared a common ancestor with the dog back in the Mesozoic, with the raven back in the Paleozoic, and with the octopus back just before when this Tapeats Sandstone was being laid down atop the eroded Precambrian unconformity. So there were a lot of routes to intelligent life, unless one defines intelligence so narrowly as to make elaborate language a requirement.
And it doesn't even take a big brain to pull off great feats of engineering -- the ants can manage quite well as a collective army with many specialized roles, being quite capable of building elaborate cities and air-conditioning them too. Or farming fungi. Or enslaving other ant species. The local ants haven't carried off our camp yet, but I have no trouble imagining a well-organized horde of specialists, complete with military policemen to direct traffic.
It is dark as we pick our way through the rocks to return to the campsite. There is, however, a group down by the boats, staying up to await the moonrise several hours from now. Another emerging tradition.
Darwin, who was his own most severe critic, asked that question himself, since he was familiar with sterile castes from his youthful days of insect collecting. He recognized it as the "one special difficulty, which at first appeared insuperable, and actually fatal to my whole theory." The answer that Darwin came up with not only saved his theory but started a whole new branch of evolutionary theory, though it began to flourish only a century later: selection, it seems, is sometimes based not on individual success but on the joint success of relatives and other group members.
In cultural terms, we have no problem understanding this theory. Whoever invented sewing helped her imitating neighbors, who were probably relatives sharing many of her genes, to survive better in a cooling climate. Even if she left no offspring herself, she increased the number of copies of her genes by her relatives' success. But what happens if biological genes are the only means for passing the information, and successes must be expressed in terms of leaving progeny? How does this get started in simpler animals without culture?
It's simple. The sterile individuals perform similarly useful work for their relatives who do reproduce, work that enhances the relatives' reproductive success markedly beyond the average. The sterile worker thus propagates copies of its genes through anothers' reproductive success. This altruism would obviously work better when helping a twin sister than when helping a second cousin.
I sometimes dream of spinning off a clone of myself to serve as my alter ago, personal assistant, errand runner, computer programmer, and library researcher -- someone who thought much as I do because of identical genes. I might even let him go through Lava Falls in my place and report about it afterward. Some insects have, in their own way, managed to get others to live for them, as when the queen bee lays all the eggs and the others do the rest of the work. This does, however, smell of slavery -- in which some ants engage, quite in addition to putting sterile relatives to work for them. Darwin doubted the existence "of so extraordinary and odious an instinct as that of making slaves" until he witnessed a slave raid himself on an ant nest near his country home at Down.
Are most of my cells therefore slaves, in need of emancipation? Is slavery a "natural" thing, somehow excusing the human slavery that persisted until this century? Questions relating biological principles to society arise whenever we start looking backwards, trying to see from whence we came, attempting to figure out rationales for our actions. And they're not easy to answer, even with great caution and care.
When this topic came up, we wound up discussing social darwinism. This, of course, has little or nothing to do with Charles Darwin; it was a pet idea of Herbert Spencer's, about which Darwin showed little enthusiasm. Science, thanks in part to its extraordinary usefulness and occasional ability to predict the future, has long enjoyed a prestige that politics does not. People arguing one or another partisan political viewpoint will sometimes try to bolster their case by borrowing from the authority of science. They usually borrow one fact or principle, out of context.
This happened earlier in the century when it was argued that laissez faire capitalism was "natural" and "scientific" -- that nature's principle of the "survival of the fittest" meant that attempts to modify monopolies were therefore unnatural and unscientific (and, undoubtedly, against God's will too, that being the traditional rationale for keeping things as they are). Railroad barons and timber magnates, captains of industry -- they all tried to argue that they were only sterling examples of self-made men, the natural ascendancy of the fittest, and that anyone could do it if they only had what it takes, that attempts to modify this "natural order" would only weaken society.
It was a great puffery and helped disguise the fact that monopolies had effectively created a lid on the ladder to keep anyone else from rising -- short, perhaps, of Hercules. (Someone noted that this was in the days before advertising agencies were brought in for such campaigns -- just imagine a catchy jingle singing "The survival of the fittest is good, good, GOOD for you!").
One still hears this argument, usually from reactionary politicians, though there is also a tendency for it to be trumpeted by "self-made men" and women, both those who have indeed, against all odds, pulled themselves up by their own bootstraps -- and by their many imitators (often, alas, hard-working professional people) who merely lack the imagination to see the role that accidents of birth and opportunity have played in putting them on the right track to success. It is often a self-serving argument, though one can sometimes hear the same argument even from the poor.
Another survival of the early social ideas stemming from the theory of evolution is the eugenics movement, that attempt to apply animal-breeding practices to humans by sterilizing the "feebleminded," the deviant, and the mentally ill. While there is indeed some tendency for the bright and the dull to run in families, the extremes -- the geniuses and the idiots -- seem to wink on and off in the population regardless of parentage. Many parents of ordinary IQ have been surprised to have a genius on their hands, and many bright parents have had to help a dull child learn to cope. A historical relative of the eugenics movement was the raising of "IQ" to a single-number quantitative index of human capacity (numbers are, of course, thought to be very scientific) and it was early applied to help decide matters of public policy: immigrants were tested en masse at Ellis Island, and there was an attempt to limit Italian and Jewish immigration because of their low scores on the tests (an early example of the cultural bias of such tests). That the eugenics movement had a limited scientific basis is now clear, in retrospect, as are some of the underlying motivations for the particular items that were selected from science to be waved about in the arguments. And given the gene shuffling that goes on, the eugenicists' schemes would probably have produced little change. Greater effects have likely been inadvertently achieved merely by sending offspring to college at an age when mate selection is at its most intense (thus promoting breeding between those able to meet college entrance requirements!).
But effects from any form of selection are likely to be small when one is talking about the present-day human population. Short of artificial selection with its complete control over an animal's reproductive life, it now seems that the evolution of large populations is very limited, contrary to what was once thought. Natural selection can most effectively act on small populations, and its sorting of the gene pool is essentially lost when they again interbreed with a larger population with its well-stirred gene pool. Permanent "improvements" perhaps occur only when complete reproductive isolation is achieved in a small geographically isolated population of animals.
Lifting natural selection out of this tangle, simplifying it into a stand-alone slogan such as "the survival of the fittest," and enthroning it in isolation as the guiding principle for success is certainly not scientific now, and never was.
Try though we must to create a better future for ourselves through social policy, we must be cautious when seeking guidelines in the animal kingdom; it may be better to use our considerable abilities to foresee the future, to imagine alternative scenarios and judge them, and create new principles to guide human society. If the animal kingdom indeed arose without planning, fortuitously finding ways that worked and exploiting them, then we should -- eventually -- be able to do better with our enhanced abilities to reflect and plan, to simulate the future in our heads (and computers) before acting to see where a course of action might lead, and thus increase our chances of success by picking the better-appearing alternative. In some areas, the principles we can create might well be superior to the shopworn principles seen in nature. But in any case, we must know our biological selves -- and that means knowing animal behavior as well -- if we are to plan and decide intelligently.
But I suppose that the main reason why people become upset with sociobiology, which one can see in any letters-to-the-editor column, is that they think that "to explain is to excuse." Yet this indignant attitude about excuses is not only uncritical but fails to understand the motivation of the scientists involved.
Take, for example, infanticide. There has been important ethological research on monkey males who kill the infants sired by another male. Some letter-writers assume that this must have been done to provide excuses for step-fathers who batter children.
In societies in which the young are especially cherished (and this includes many primate societies), infanticide is puzzling as well as repugnant. But there is indeed a devil's payoff for infanticide under some conditions in the animal world, such as harem mating systems in which the male-in-charge is regularly replaced every few years, the new one proceeding the kill off infants. The ex-mothers, no longer breast feeding and thereby producing hormones that suppress ovulation, will come into heat -- and can thus be impregnated by the male taking over the troop a year sooner than otherwise. Since his reproductive years are limited by the mating system to those several years when he can manage to hold onto the top slot, this practice may double the offspring he leaves behind. If the tendency to kill infants upon taking over is inheritable, then a new generation of males may come to carry that trait. Indeed, our close relatives, the gorillas, are apt to suffer a wave of infanticide when a new silverback male takes over the harem. To reveal the chain of mechanisms involved in infanticide is to understand how genes for such murderous behavior arising by chance could have been preserved in evolution.
This odd sexual-selection mechanism, in these harem-less days of bottle feeding and birth control, probably wouldn't operate anyway in our society, even if battering infants to death were socially acceptable. But if such genes were left over from some harem-ruling ancestors, it might give some insight -- without in the least condoning or excusing their behavior -- into potential subconscious motivations of battering step-fathers.
Though a whole book would be needed to adequately explore the subject, this possible evolutionary scenario does demonstrate the physiological and evolutionary mechanisms by which genes for murder could be promoted by a harem-type mating system. As a reflective society we can elect to promote the opposite, such as outlawing harems. We have long known that society must combat murder and child abuse; knowing that there can be a genetic underpinning for infanticide doesn't excuse it, even though it may help us devise better ways of educating battering step-fathers. Rather than looking to behavioral research for excuses, we should value it for the new directions it can suggest in solving our problems as a society. What's natural isn't always a good policy anymore, nor a good excuse.
When we die there are two things we can leave behind us: genes and memes [contributions to culture to be mimicked]. We were built as gene machines, created to pass on our genes. But that aspect of us will be forgotten in three generations. Your child, even your grandchild, may bear some resemblance to you, perhaps in facial features, in a talent for music, in the colour of her hair. But as each generation passes, the contribution of your genes is halved. It does not take long to reach negligible proportions. Our genes may be immortal but the collection of genes which is any one of us is bound to crumble away. Elizabeth II is a direct descendant of William the Conqueror. Yet it is quite probable that she bears not a single one of the old king's genes. We should not seek immortality in reproduction.
But if you contribute to the world's culture, if you have a good idea, compose a tune, invent a sparking plug, write a poem, it may live on, intact, long after your genes have dissolved in the common pool. Socrates may or may not have a gene or two alive in the world today... but who cares? The [cultural contributions] of Socrates, Leonardo, Copernicus, and Marconi are still going strong.
......the sociobiologist RICHARD DAWKINS, The Selfish Gene, 1976
I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little or make a poem which children will speak for you when you're dead.
......the playwright TOM STOPPARD, The Real Thing, 1984
Any suggestion that the child's mathematical ineptitude might have a genetic origin is likely to be greeted with something approaching despair: if it is in the genes "it is written", it is "determined" and nothing can be done about it; you might as well give up attempting to teach the child mathematics. This is pernicious rubbish on an almost astrological scale. Genetic causes and environmental causes are in principle no different from each other. Some influences of both types may be hard to reverse, others may be easy.
......the sociobiologist RICHARD DAWKINS, The Extended Phenotype, 1982
The behavior of animals is determined mostly by evolution, while humans have options for self-improvement in line with their civilized ideals.
......the primate ethologist SARAH BLAFFER HRDY, 1983.
Socrates was put to death in 399 B.C. on the charge of corrupting the youth of Athens. He subjected traditions and custom to the fire of pure reason and in so doing threatened the traditions of the society. As one of the first and greatest philosophers and as one who unhesitatingly espoused reason, he showed us once and for all that it is possible to break with tribal lore, traditions, and the cultural luggage that we have brought into the world and look at ourselves anew, in the light of reason. Socrates, more than any other teacher, has shown us that we need not be slaves to the promptings within, the whispers from the limbic lobes. That is where our genes speak, where they hold our hearts: reason alone can free us from their ancient leash.
......the anthropologist BERNARD CAMPBELL, Human Evolution, 1985
It used to be thought, in the bad old days of social Darwinism when evolution was poorly understood, that life is an uninterrupted struggle -- "nature red in tooth and claw." But this is only one side of natural selection.... The same process also leads to altruism and reciprocity in highly social groups. Thus the human species has evolved genuine sentiments of obligation, of the duty to be loving and kind.... In this sense, evolution is consistent with conventional views of morality.
......the philosopher MICHAEL RUSE and the sociobiologist EDWARD O. WILSON, 1985