Just So Stories
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Perhaps the most damaging criticism aimed at the theory of evolution consists of the claim that the theory gives us nothing more than a collection of Just So Stories. That derisive term refers to Rudyard Kiplingís collection of short stories, published in book form in 1902, many of which offer a fanciful explanation of how some feature of the natural world came to exist as such. Of course, the theory of evolution itself does not succumb to that criticism because, as a theory, it consists of a set of hypotheses that scientists have proven and verified with strong evidence. On the other hand, many popular expositions do, indeed, have the character of Just So Stories and thus can serve to bring the theory of evolution into disrepute. By examining how that happens we may hope to gain some insight into how our use of language can mislead our thinking.
Kiplingís story "The Elephantís Child" gives us a perfect example of a Just So Story. In that story Kipling introduced his readers to "...an Elephantís Child - who was full of Ďsatiable curtiosity, and that means he asked ever so many questions." The incident around which the story revolves begins with the Elephantís Child "...going to the great grey-green, greasy Limpopo River, all set about with fever-trees, to find out what the Crocodile has for dinner." At the river the Elephantís Child, with "...only a blackish, bulgy nose, as big as a boot", finds the Crocodile and asks him what he has for dinner. The Crocodile offers to whisper the answer to him, so the Elephantís Child puts his head down and the Crocodile bites down on his nose. Then follows a tug of war in which the young elephantís nose gets stretched out into a tentacle-like tube. On his return home the Elephantís Child discovers that he can do many useful things with his newly elongated nose, so all of the other elephants, after learning of this, go to the river to have their own noses lengthened. And, Kipling assured his readers, "...ever since that day, O Best Beloved, all the Elephants you will ever see, besides all those you wonít, have trunks precisely like the trunk of the Ďsatiable Elephantís Child."
Of course, no scientist would accept that story as an explanation of why the elephant has a long prehensile trunk. The story contains several features that conflict with the theory of evolution. We can identify those features and learn how to recognize them. Then we can then figure that any explanation that displays any of those features falls into the realm of the Just So Story, which lies fully outside the realm of science.
First, we have a version of the pathetic fallacy, the ascribing of properties that only humans can possess to animals or other non-human things, which we might call the Disney factor. We discern that factor in any story in which we see human-like intentions attributed to animals, such as elephants. I found a good example of this factor in a newspaperís description of a discovery made in 2008.
Paleontologist David J. Varricchio, of Montana State University in Bozeman, and his team reported finding good evidence that male theropod dinosaurs sat on their nests and incubated their matesí eggs, as most birds do today. Because the current theory has birds evolving from one line of theropods, the group that includes the Tyrannosaurs and the Velociraptors, this discovery gives us an indication of how far into the past we can go and still find this instinct in the ancestors of the birds. That discovery in itself and its simplest interpretation do not put the Disney factor onto the Troodon and Citipati dinosaurs whose fossils the group studied, but a statement in the Los Angeles Timesí report on the discovery (2008 Dec 20, Pg A15) does: "Additionally, since unhatched chicks needed so much heat to stay warm," the article stated, "the dads may have had little choice but to help out with the incubation if they wanted their offspring to survive,...."
We have now to question whether a creature that, as far as we know, had the intellectual capacity of an ostrich could choose or want anything. In fact, Troodon and other theropods had less than "little choice": they had no choice at all in the matter. Once the earliest theropods had evolved the phenomenon of male incubation of the eggs, presumably due to environmental shaping of the appropriate mutations, they had made almost impossible a return to males not incubating their matesí eggs. A male theropod that left his mateís eggs untended would not likely pass his genes back into his speciesí gene pool, thereby ensuring that the genes that direct (or donít direct) his behavior eventually disappear from his species, leaving only the genes that create males with the instinct to incubate their matesí eggs. Consider the fact that over ninety percent of bird species employ male incubation of their eggs and compare that with the fact that in less than five percent of mammal species do the males show so much care for their young. A male theropod that does not incubate his mateís eggs does not thereby express a choice, but rather a genetic defect.
Likewise, the theropod could not want his offspring to survive. In order to do that he would have needed to possess the knowledge that sitting on his mateís eggs would lead to the survival of his offspring. He would have needed to have a language and a culture that could store and transmit that knowledge as a commonly held memory of a previous discovery. He and his species would have needed to have the ability to think and to plan as we do. But birds donít have language and culture, so we can reasonably believe that theropods didnít either. Instead, we infer that the male theropod simply recognized his own nest, as birds do, and that if he saw eggs in the nest, he got the urge to sit on them. We may well ask how such instincts evolved and what brain structures produce them, but we know from observations of many different kinds of animals that such elaborate instincts do exist. The newspaper article might better have said, "Unhatched chicks needed heat to stay alive and continue developing, so their fathers had an instinct to incubate the eggs because those who did not have that instinct died out."
Second, we have what we might call the Lamarckian factor when we have a story telling us that some feature of the environment made a lasting change in a species by altering one or a few members of that species through direct action. We see a prime example of this factor in a story common among Native Americans, a story called, depending upon who tells it, "Why The Bear Has No Tail" or "How The Bear Lost His Tail".
The title tells us implicitly why we have such a story at all. As a rule predatory mammals have long tails. Think of the fox and the wolf, the mountain lion and the coyote, the otter and the weasel. In the set of creatures that we label "predatory mammals" the bear stands out for having essentially no tail. That kind of anomaly irritates something within our minds and we use stories to scratch that itch. Native Americans responded to that itch with an intuitive understanding of what Wilhelm Gottfried Leibniz formalized as the Principle of Sufficient Reason: if a phenomenon goes one way when it could have gone another way, it must have had a reason for going the one way and not another way. So why, we must ask, does the bear have no tail when he could presumably have had a long tail like other predators?
One winter, the story tells us, in a time when bears had long tails, a bear woke up from his hibernation and went looking for something to eat. Apparently he didnít get enough to eat the previous summer, so his empty, grumbling stomach woke him from his winter nap. Soon he met a fox, who had stolen a fish that an otter had caught and left unguarded. The bear asked the fox whence he got the fish, commenting that he wanted to get some fish for himself to eat. Not wanting to confess his theft and having a mischievous streak, the fox told the bear that he cut a hole in the ice on the lake, stuck his tail into the hole, and when the fish bit his tail he pulled it out. Because he usually sleeps all winter, the bear had little knowledge of the freezing-cold world into which he had ventured, so he decides that he will try the foxís ploy himself. So he went to the lake, gouged a hole in the ice with his claws, then put his tail into the water in the hole and sat down to wait for a fish to bite it. Time passed and nothing happened. The bear started to feel cold and decided to go elsewhere to find food. But when he tried to get up he discovered that the water in the hole had frozen and, thus, that his tail was locked in the ice. Afraid of freezing to death, he jumped up and the force of his leap tore his tail off. Ever since that day bears have had no tails.
Because we understand the concept of heredity, we donít accept that story as a proper scientific explanation of why bears have no tails. We understand that the bearís children would not have inherited his lack of a tail (if only because Mrs. Bear did not lose her tail). Putting it in technical terms, we say that natural selection acts on genotype, not on phenotype. That goes to say, the environment can only produce a lasting change in a species by acting on its heredity and not by acting simply on the expression of that heredity. Contrary to Lamarck, we say that living things do not inherit acquired characteristics.
And third, though Kipling did not manifest it in any of his stories, I add what I call the Spencer factor to the list of traits that we find in a Just So Story. Named after Herbert Spencer, who devised and promoted the term "survival of the fittest", this factor comes manifest in stories that appear to employ the theory of evolution, but which, in fact, misuse it. We can discern this factor in a story that we might conceive as the scientific analogue of an urban legend Ė the story of hypertension among African-Americans.
It began with the realization that almost 35 percent of African-Americans suffer from hypertension while only 25 percent of the general population in the United States of America does so. An even smaller percentage of rural Africans develop hypertension, which means that we have an anomaly that we want to explain. One popular hypothesis has it that many of the Africans brought onto slave ships died from salt-wasting diseases, so that the survivors had a tendency to retain salt and thus had a predisposition to hypertension.
That actually seems like a reasonable hypothesis, one that certainly looks like it conforms to the Darwinian theory of evolution by "descent with modification". We start with a population of Africans, whose bodies have a wide range of salt-retaining ability, and subject them to an utterly brutal Middle Passage that preferentially kills off, through diseases that deplete the bodyís supply of salt, those with a low ability to retain salt, thereby leaving a population of survivors with a higher proportion of people who have a high ability to retain salt in their bodies. Voila! We get higher rates of hypertension, which comes from excessive salt retention. So why have I put that hypothesis under Just So Stories?
I do so because the slave-ship hypothesis reflects a carelessness with the theory of evolution. When we present an hypothesis to explain some feature of the living world, we require that the hypothesis fit the evidence, however little of that we may have. We also require that alternative hypotheses that accord with the evidence that we have come under consideration and that we only dismiss those alternatives for good cause. In fairness, we must admit that meeting those requirements does not come easily, as I will demonstrate.
As for the evidence, we have records from the time of the slave trade, roughly AD 1600 to AD 1800, and historians have found that the leading causes of death on slave ships were tuberculosis (which is not a salt-wasting disease) and acts of violence. They have found no evidence to support the assertion that salt-wasting diseases occurred more frequently on slave ships than they did on land. Without evidence for the operation of its particular selection mechanism, the hypothesis fails the fundamental test of any scientific theory.
Do we have any alternative to the slave-ship hypothesis?
High blood pressure does not come only from the bodyís ability to retain salt. Chronic stress also provides a risk factor for the development of hypertension. So shouldnít we suspect that excessive hypertension in black Americans has some relation to the stress of coping with life in a racist society? In light of that question a cynic might guess that the slave-ship hypothesis got devised for the purpose of preempting any consideration of the possibility that excess hypertension among black Americans has a more recent cause. It looks like an effort to push responsibility for the disease further back in time, thereby weakening the moral demands upon us.
That suggestion falters on the knowledge that Africans who have emigrated to Europe in recent decades also show an increase in the rate of hypertension. But modern Europe does not have in its culture the kind of vicious racism that long existed in the United States of America and in some small parts of the country still does. So we donít have good evidence to support a racism-stress hypothesis.
Perhaps we could look to the stress of modern urban living? But that stress comes over all of us, so it doesnít seem to offer an explanation as to why it preferentially affects black people. We might expect that the higher proportion of black Americans who live in poverty might have some influence, but I want to suggest another possibility, one that I have not seen before now.
In 1840 Julius Robert Mayer (1814 Nov 25 Ė 1878 Mar 20), working as a shipís physician, bled a sailor in Djakarta, Indonesia. Still part of medical practice at the time, bleeding involved removing a quantity of a patientís venous blood through a tube and discarding it, along with the poisons that doctors presumed it contained. Mayer was surprised by the observation that the sailorís blood coming into the tube was red: in more temperate climates it was darker, almost purple. Mayer attributed that observation to the tropical heat, reasoning that the sailorís body didnít need to use as much oxygen as normal to maintain its temperature. That discovery led Mayer to lay the groundwork for the discovery of the theorem of conservation of energy, but we can draw another lesson from it.
If native Europeans coming to the Tropics do not use all of the oxygen that their blood can carry, then perhaps the converse stands true and native Africans coming to the temperate zone need more oxygen than their blood can normally carry. In that case the blood must flow faster within the body and, as we learn in basic hydrodynamics, that requires a higher pressure pushing it. Making the heart work harder then leads to chronic high blood pressure. There we seem to have our answer and it certainly seems to meet the requirements of the theory of evolution. We have not Spencerís "survival of the fittest", but, rather, preferential reproduction of those individuals who fit most perfectly into their ecological niche. That formulation of the theory leads us to expect that creatures that have evolved circulatory systems that provide the right amount of oxygen, neither too much nor too little, to meet the basic demands of their environment may develop diseases of the circulation when they leave that environment.
That low-oxygenation hypothesis makes sense, but so, at first, did the slave-ship hypothesis. So how do we know that the low-oxygenation hypothesis doesnít give us anything more than another Just So Story? I donít know of any evidence pertaining to low oxygenation of transplanted tropical peopleís blood, so I canít offer the Scientific Methodís slam-dunk. Scientists clearly have the option of obtaining evidence that will test that hypothesis, so properly we should wait and see what they find. But suppose they didnít have that option in this case. On what basis then could we accept this hypothesis as a legitimate part of the theory of evolution?
We accept it on the basis that the theory of evolution itself stands subject to a process analogous to natural selection. Just as a species evolves to fit as neatly as possible into its environment, so the pieces that we put into the puzzle of the theory of evolution must have shapes that fit their positions in the puzzle. As far as we can tell the low-oxygenation hypothesis fits best into the part of the puzzle pertaining to the excessive hypertension in African-Americans. We can thus accept the hypothesis into the theory contingent upon the finding of evidence or of a better hypothesis.
So now we know what to discard from consideration as pieces of the theory of evolution:
1. We must reject any statement that imputes to non-human life-forms intention or foresight, any ability to plan or to seek goals beyond the immediate present. If we discern any phenomenon that resembles planning, we must interpret it as instinct and find an evolutionary explanation for it on that basis.
2. We must reject any statement that has a life-form passing on to its progeny any trait that it has acquired by direct interaction with its environment. An antelope may, over a lifetime of striving to reach the leaves of trees, develop a long neck, but its offspring wonít inherit that long neck and thereby become giraffes.
3. We must reject any statement that over-applies the theory of evolution. We must take care that we do not use natural selection to explain phenomena that we can explain in other, more reasonable, ways.
So how did the elephant get its trunk? Evidence to support any hypothesis will not come to us easily, if at all: soft body parts donít fossilize. In the rare instances in which paleontologists have found evidence of soft body parts, they have found casts of them, impressions made in mud that then hardened and turned to stone. We cannot count on anyone finding casts of dead elephants that display the full evolution of the creature. We have to work out the evolution of the trunk logically, see how well it fits the wider picture of the evolution of large mammals, and then accept it contingently pending the discovery of evidence that pertains to it.
We gain our first clue from the fact that all mammals have flexible, muscular lips that they use to hold their food and pull it into their mouths. The rhinoceros gives us a good example of what the earliest proto-elephant must have looked like. It simply has an elongated upper lip, only a few inches longer than the lip its remote ancestor had. Using its prehensile upper lip to grab and hold food as it eats doesnít give the rhinoceros any advantage in times of plenty, but when the rhinoceros population exceeds its food supply (either by over-reproducing or by famine), the more efficient eaters will survive better than the less efficient ones and will thus reproduce themselves more extensively. In time we get a population of rhinoceroses that all have the prehensile upper lip. That change, we infer, happened in the far past to the rhinoceros population. It also must have happened to the proto-elephant population and done so repeatedly, each repetition of the process, spreading a new mutation throughout the population, producing animals with ever longer trunks.
We gain our second clue from the fact that the trunk does not represent only the elephantís nose: it consists of the elephantís upper lip and nose together. As elephants gained longer trunks they also gained the ability to smell things without getting too close to them and to explore a wide smellscape without expending a great deal of effort. Further, a proto-elephant with a long enough trunk could get water from a river while still keeping a watchful eye on the surrounding water for signs of an approaching crocodile. Such an animal would thus have an advantage over one that had a shorter trunk; it would thus have a greater chance of avoiding death long enough to leave a large number of offspring to carry its genetic coding onward. This factor tells us something about the mutation that led to the elephantís trunk if we ask ourselves why the rhinoceros does not also have a long trunk instead of an elongated upper lip. It tells us that the mutation so fused the end of the nose to the upper lip that any elongation of the upper lip would carry the nostril openings with it.
Thus we have a proper hypothesis to explain how the elephant got its trunk. Not as poetic or fanciful as Kiplingís version, certainly, but one more appropriate to a scientific endeavor. By comparing the two we can see the distinction between a Just So Story and a proper scientific hypothesis.
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