Darwin Got It Right
Charles Darwin’s theory of evolution was attacked by virtually all of his academic colleagues when he published On the Origin of Species in 1859. Darwin’s theory still remains controversial. When surveyed, about 40 percent of Americans and 25 percent of Britons still say that they don’t “believe” in evolution. The word “believe” is significant because a statement affirming belief may be relevant if the question concerns the Virgin Birth or the Tibetan deity Mahakala, but accepting any scientific theory—gravity, evolution, global warming—rests on whether it correctly predicts observable events. But Darwin would have been amazed, perhaps dismayed, by the continuing flood of scholarly books and papers that attempt to show that he was wrong.
However, it’s first necessary to understand what Darwin actually proposed. Although Darwin was unaware of genes or DNA and obviously lacked access to the overwhelming body of evidence that has since supported his theory, he got it right. The basic premises and research paradigms of evolutionary biology, stated in a clear manner in the first edition of On the Origin of Species, are still valid. You, yourself, can judge whether this is the case because the Origin is free of jargon; biological jargon hadn’t been invented. I’ve used a facsimile edition for many years in my courses.
Darwin also raised issues that transcend the debates that usually occupy academics, issues that are relevant today, such as family planning and the impact of human activity on the environment. He showed that seemingly neutral changes driven by political and economic forces can have profound consequences on the environment. English villages and towns, for example, once had “commons,” the green open spaces, often ringed by eighteenth- and nineteenth-century homes that grace New England towns. The common was a place where anyone could graze livestock, but in the early years of the nineteenth century a land-grab occurred. The commons were privatized and “enclosed.” The ecosystems within the walled and fenced enclosures quickly changed. Absent grazing livestock, plants, shrubs, and trees sprung up. In turn, the insects, birds, and animals living within the enclosures totally changed.
The finches that Darwin had collected and observed in the Galapagos Islands during his voyage on the Beagle played a central role in Darwin’s thoughts on the “transmutation” of species. The 13 different Galapagos finch species have different food sources, insects living in the ground, cactus seeds, and different types of nuts that determine the shapes of their beaks. Darwin became convinced that the different species had each been transmuted through a series of small changes to best exploit particular ecosystems. It has since been shown that changes in rainfall rapidly change the selective forces acting on the birds. For example, dry weather favors the survival of finches that have short, strong beaks capable of splitting open hard-shelled seeds; wet weather favors long thin beaks. Changes in the ecosystem, shifting the selective forces on the bird population, in turn affect the birds’ behavior and bird calls (Podos, 2001).
The Tenuousness of Life and Natural Selection
Darwin also was aware of the earlier evolutionary theories of his grandfather, Erasmus Darwin, and John-Baptiste Lamarck. On his return to England from his voyage on the Beagle in 1835, Darwin was wondering how the fossils of extinct animals that he had found in South America could fit with theories that posited the immutable nature of species. However, the missing element in previous evolutionary theories was a directing mechanism that did not involve divine direction. Darwin’s notebooks show that he grappled with this problem for years. The insight that provided the solution derived from a problem that is still with us—human population growth. Europe’s population had been almost static since the sixteenth century until it began to increase during the eighteenth century and doubled by 1900.
Romantics may yearn for the “good-old-days” in preindustrial Europe. Life was pleasant for the privileged few, but as Robert Fogel points out in his book The Escape from Hunger and Premature Death, 1700–2100, life was miserable for almost everyone else. In the early years of the nineteenth century:
The supply of food was not only meager in amount, but also relatively poor in quality. . . . Even prime-age males had only a meager amount of energy available for work (Fogel, 2004, p. 9).
Into this ecosystem came the first fruits of public health. We can all be thankful that virtually everyone ignored Victor Hugo’s agricultural advice. In his novel, Les Misérables, in a discourse set apart from the story of Inspector Javert’s relentless pursuit of Jean Valjean, Hugo lamented the fact that farmers were no longer using “night soil” (human waste) to fertilize their crops.
The segregation of human fecal material from the food and water supply was introduced on a broad scale in Europe. Communicable diseases decreased, and an extraordinary increase occurred in lifespan and population size. In 1750, 75 percent of all children born in London were dead before their fifth birthday. Life expectancy in England was 37 years. Life expectancy in France was only 26 years. But over the next fifty years, sanitation improved and Europe’s population doubled. By the year 1810, 78 percent of all children born in London lived past their fifth birthday. The population of Europe was increasing at an unprecedented rate. Thomas Malthus’s 1798 tract, An Essay on the Principle of Population, predicted incipient disaster. Malthus thought that the population surge was outstripping the food supply. Famine, pestilence, disorder, and war would result.
The impending disaster never happened because agricultural production outpaced population growth, but Malthus’s “essay” led to Charles Darwin’s “Eureka” moment. On reading the essay, Darwin realized that the
doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms, for in this case there can be no artificial increase of food, and no prudent restraint from marriage . . . and a struggle for existence inevitably follows from the high rate at which all organic beings tend to increase (Darwin, 1859, p. 63).
Darwin’s terminology, the “struggle for existence,” probably led to Alfred Lord Tennyson’s view of “Nature red in tooth and claw,” and to films on evolution beginning with scenes of lions devouring their prey. However, Darwin stated instead that
I use the term Struggle for Existence in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny (Darwin, 1859, p. 62).
Natural selection, the key element of Darwin’s theory of evolution, followed from this insight. As Darwin put it,
any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring also will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a few can survive. I called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection (Darwin, 1859, p. 61).
Variation is the feedstock for natural selection. Darwin’s anatomical studies of barnacles that had occupied him for decades came to an end in 1854. His detailed monographs had earned him a Royal Medal for Natural Science from the Royal Society, but the major effect was on evolutionary theory. Darwin had observed the pervasive nature of variation and the gradual changes in structure from one generation of barnacles to another until, as Janet Browne put it (1995, p. 512), he realized that “animals became so distinct from their parents and cousins that they could be called a different species.” As we shall see, evolutionary psychologists fail to take account of variation.
Darwin was attempting to explain his theory to readers who were not “natural philosophers,” the cover term in that era for biologists, archaeologists, geologists, and anthropologists. The first chapter of On the Origin of Species introduces the key elements of natural selection in contexts that would be familiar to his readers. To this end, Darwin discusses the role of variation and guided selection by agriculturists who produced large juicy pears and vivid flowers, and animal breeders who bred fast racehorses and fat cattle. Darwin throughout his life assiduously sought out information from horticulturists, farmers, and animal breeders. Darwin joined pigeon fanciers’ clubs and conducted his own pigeon-breeding experiment aimed at demonstrating that “long continued” selection acting on small variations in time produced breeds of domesticated pigeons so great that, “if shown to an ornithologist, and he were told that they were wild birds, would certainly, I think, be ranked by him as well-defined species” (Darwin, 1859, p. 22).
The fossil record of hominin evolution shows that Darwin was right when he stressed the role of small differences in natural selection; “slight variations” can have profound effects. The grinding action of our teeth, which acts as a food mill, increases the absorption of nutrients about five percent compared to just swallowing big chunks. A dental research group in Boston in the 1960s was testing dentures that had sharp steel edges, enabling denture wearers to easily grind up their food. But anyone who could afford to buy a second pair of false teeth would not find it difficult to buy more food, and the dentists abandoned the project. The five percent gain wasn’t worth the expense and the risk of lacerated tongues. However, in the state of nature, food is not always abundant. The changes in tooth morphology that occurred millions of years ago in early hominins made it possible to absorb slightly more nutrients from a limited supply of food. Hominins thus lost the interlocking canines that prevent apes from performing the grinding motions that can mill food down into a slightly more digestible mush. Paleontologists often claim that they have found a new early hominin species based on the evidence of a single tooth.
It’s easy to forget that food still is a scarce commodity in most parts of the world—my wife and I have seen horrifically stunted and wasted children in remote villages in the depths of Nepal. Life in these isolated, roadless regions is a time-capsule view of times past. If the crops fail, everyone is reduced to digging up and eating roots.
Did Natural Selection on Humans Ever Stop?
As I’ve already noted, according to evolutionary psychologists such as Marc Hauser, human attributes such as morality result from our having a “moral gene” that evolved and never changed sometime before 100,000 years ago, perhaps 300,000 years ago. (Hauser never explicitly gives the date.) Stephen Dawkins claims that we favor our close relations because we have a “selfish gene.” And the basic premise of Noam Chomsky’s widely accepted linguistic theory is that all human brains contain genetically transmitted “knowledge of language” that specifies the details of syntax of all human languages. To that end, Chomsky’s views on language haven’t changed since 1976, when he stated that
language is as much an organ of the body as the eye or heart or the liver. It’s strictly characteristic of the species, has a highly intricate structure, developed more or less independently of experience in very specific ways, and so on (Chomsky, 1976, p. 57).
In his subsequent papers and books, the specific operations that Chomsky’s hypothetical language organ is supposed to carry out have changed, but it remains an innate, species-specific entity. According to Chomskian theories, the syntactic rules, speech sounds, and syllable structures of the particular language that a child hears are acquired because “parameters and principles” that activate them have been preloaded into every child’s brain. In computer-speak, according to Chomsky we have preloaded software that automatically selects the appropriate instruction set for whatever language a child encounters in the first years of life. It’s similar to clicking on the box for English when you open the software installation wizard, except that it’s automatic—you don’t have to mouse-click on “English.”
In substance, Chomsky’s claim is that children do not really learn language in the way that they learn to use forks or chopsticks. I have yet to see anyone proposing an “organ” that specifies genetically transmitted motor acts that enable a child to “acquire” the ability to use a fork or chopsticks, but that’s precisely what Chomsky proposes for human language. If we were to substitute “table habits” for “language,” a similar theory would have us believe that the maneuvers that are necessary to use chopsticks and forks derive from an innate knowledge base built into every child’s brain. The “rules” for using chopsticks would be activated if a child grew up in China. The fork rules would be activated in settings in which forks were used. Different fork protocols, “fork dialects,” would be preloaded into every child’s brain to account for the way that forks were used in England and the United States.
There is more to Chomsky’s theory—supposedly no child would “acquire” any language unless this preloaded language-software was in his or her brain. According to Chomsky and the linguists, philosophers, and psychologists who share his views, children would not be able to acquire any language because insufficient information is present in the ill-formed utterances that children hear in the early years of life. The linguistic term used to justify this claim is “the poverty of the stimulus.” Since any child from anywhere can acquire any language if she or he is raised in a normal environment, then it follows that every human child must possess the same preloaded “knowledge of language” (another linguistic term). In short, no variation exists. Because there are people living all over the world, this store of “knowledge of language” must have evolved before the period in which modern humans left Africa. That must be the case because humans evolved in Africa and later colonized the rest of the world.
One recent estimate is that a number of migrations out of Africa occurred—the most recent being about 80,000 years ago (Templeton, 2002). Moreover, everyone did not leave Africa 80,000 years ago, and it is clear that the descendants of the Africans who were abducted or voluntarily migrated in the last thousand years or so have no difficulty acquiring English, Spanish, Portuguese, Turkish, or any other language. So if Chomsky is correct, the language organ, which he termed the “Universal Grammar,” must have evolved and become genetically specified in every “normal” human brain well before that date. In short, since any child will acquire any language with native fluency if she or he starts before age seven years, the genetic substrate for Chomsky’s hypothetical “knowledge of language” must have formed and fixed forever before the dispersal of humans from Africa, else it would be the case that some ethnic groups would be incapable of acquiring particular languages. The archaeological, genetic, and fossil evidence that will be discussed in chapters 4 and 5 pushes the date back to 250,000 years or so in the past.
Natural Selection on Humans Never Ended
But there is a problem. The only plausible mechanism, unless we really want to fall back on mechanisms related in Genesis, the Popul Vuh, or other creation myths, is natural selection. As Darwin pointed out, any biological attribute,
if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring (Darwin, 1859, p. 61).
If we read “infinitely complex relations” as the “ecosystem,” which for humans is their “culture,” we will be in tune with current views on the complex relations that hold between living organisms, natural selection, and the ecosystem.
We know with certainty that some aspects of human behavior have a genetic basis that resulted from localized, culturally mediated natural selection. For example, Asian ancestry often precludes adults drinking milk or eating milk products without unpleasant consequences. Asians as a group (a population, to use the biological term) tend to lack the genes that allow adults to digest milk. Not everyone can digest lactose. You can see this on the shelves of your local supermarket, which stocks lactose-free foodstuffs. Natural selection for adult lactose tolerance occurred independently in cultures in which cows, goats, or sheep were domesticated. The animals most likely were first domesticated for meat. Over time, natural selection for lactose tolerance after childhood occurred because an additional source of food was an asset in the “struggle for existence.” Evolution for adult lactose tolerance, in fact, occurred on different genes in different places at different times. The most recent documented event happened in Kenya. Cattle were introduced from Ethiopia. A “selective sweep” on a gene that mutated, allowing adults to digest milk, occurred within the last 3,000 to 7,000 years. Cattle had been introduced from Ethiopia, and milk then became available for adult consumption.
The term “selective sweep” simply means that practically everyone ended up having the gene because the individuals who had this gene were more likely to survive, as well as their children. Over time, the proportion of people living in Kenya who had the adult lactose tolerance gene became overwhelming. Moreover, lactose tolerance in Kenyans and individuals whose ancestors lived in Kenya occurs from natural selection for a gene that differs from the genes that confer lactose tolerance in people who have ancestors who lived in Northern Europe (Tishkoff et al., 2007). The mutations that enabled adult lactose tolerance after childhood occurred in cultures that had domesticated herds. Natural selection for these genes increased the available food supply, thereby enhancing survival—no mystery, very simple. It is important to keep in mind that adult lactose tolerance cannot be learned or imitated—it derives from a biological trait that has a genetic basis and thus is subject to natural selection.
Humans have spread across the world to live in places that would seem improbable to their African ancestors. Tibetans have lived at altitudes over 3,500 meters and often as high as 5,300 meters above sea level for at least 5,000 years, perhaps more than 7,000 years. Surviving at these extreme altitudes means breathing air that has less oxygen. This fact has resulted in unique Tibetan biological attributes that are as unique as the Buddhist rites that mark Tibetan culture.
Tibetan culture spread during this period beyond the boundaries of present-day Tibet. My wife and I have cumulatively spent years in Nepal, India, and Tibet studying and documenting Tibetan paintings and rites. In these regions, it quickly becomes apparent when you climb over 5,000-meter-high mountain passes that Tibetans also have unique biological traits that allow them to better cope with life at these extreme altitudes. Quantitative physiologic studies show that Tibetans can function with much lower levels of oxygen in their bloodstream. The birth weights of infants born to Tibetan women in Lhasa, Tibet, at an altitude of 3,500 meters above sea level are, on average, 500 grams heavier than the babies of lowland Han Chinese women (Moore et al., 1998). Sherpas, a Tibetan group who migrated to Eastern Nepal about 350 years ago, are renowned for their ability to cope with the altitudes reached when climbing 8,000-meter-high Himalayan mountains. Over the nine years that my research group studied climbers ascending Mount Everest, it became clear that it would be impossible for virtually any “member” (the term for non-Sherpa expedition members) to reach Everest’s summit without Sherpa assistance.
As chapter 2 pointed out, Mount Everest is climbed in stages by virtually everyone who isn’t a Sherpa. Members first climb up from base camp at 5,300 meters to camp 2 at 6,300 meters (camp 1 is a temporary site), then at a later date from base camp to camp 2 and then on to camp 3, finally reaching camp 4 at 8,000 meters, and if all goes well ascending from camp 4 to the summit and returning to a lower camp. All of the tents, stoves, oxygen cylinders, fuel, and food are carried up and set up by Sherpas. The Sherpa ice-fall “doctors” also place ladders over the crevasses leading up over the ice fall (a moving, descending, tongue of a glacier) leading to camp 2. Sherpas carry up miles of rope and hundreds of snow stakes and ice screws, which they set up as a safety-line up the steep slope between camps 2 and 4. On a radio link one afternoon, I heard an exhausted “member” of our expedition, who had reached camp 3, fixating on hot tea. A Sherpa who also was on the radio link then climbed up 1,000 meters to camp 3 from camp 2 to deliver a thermos full of tea, and then returned to camp 2—all in a day’s work.
Two independent genetic studies confirm that there is a genetic basis for Sherpas and other Tibetans being able to cope with life at extreme altitudes. Selective sweeps on the genes responsible for Tibetan extreme-altitude adaptations occurred in the last 3,000 to 4,000 years (Simonson et al., 2010; Yi et al., 2010). Their adaptation clearly is the result of natural selection acting on the pool of variation present in the human population at large. If you were to take 100 people at random off the street in Amsterdam (where the altitude is at, or slightly below, sea level depending on what street you’re on), put them on a treadmill, and measure how much air they are breathing as they run, you’ll find that some people need 1/10 the amount of air as other people when they run at the same speed. The differences are thought to follow from differences in the efficiency at which peoples’ lungs transfer oxygen to the bloodstream (Bouhuys, 1974). In Tibetans who have been living year-round at altitudes up to about 5,400 meters for thousands of years, Darwinian natural selection has acted to favor the survival of those individuals and their children who had better respiratory efficiency.
Other recent studies point to natural selection acting on Bushmen in Africa to allow them to cope with kidney functions in extremely arid conditions and Bantu genes associated with bone density reflecting the environmental pressures of different human settings. If some attribute is essential for successful adaptation to an ecosystem, whether it’s a finch or a human, natural selection will kick in. Geography, not surprisingly, plays a part in setting animals and plants on different genetic pathways. In the jargon developed by evolutionary biologists since Darwin’s time, geography is a genetic “isolating mechanism.” But other factors come into play in humans. Human languages and dialects act as genetic isolating mechanisms, yielding observable genetic differences in groups living in close proximity (Barbujani and Sokal, 1990; Belle and Barbujani, 2007). Put simply, men and women tend to mate and have children with someone who can understand what they are saying!
Why You Can’t Speak Proper English if Your Ancestors Were Chinese
But these genetic distinctions have nothing whatsoever to do with their children’s ability to learn any other language. If Chomsky were correct—that a child needs genetically transmitted (preloaded) “knowledge of language” to acquire her or his native language, we should expect to find that natural selection yielded different Universal Grammars (UGs), the preloaded knowledge bases that are necessary to acquire a language, in people whose ancestors have been speaking different languages for long periods.
Nothing in the room that you may be in while reading this book, nothing on your person, nothing that you find necessary for daily life, has an innate, genetic basis. Language clearly is the principal instrument whereby culture is transmitted. Everything that you use, wear, see, or hear is the result of cultural aggregation and cultural transmission. Virtually all of the aspects of human behavior that enhance our fitness relative to that of other species are culturally transmitted through the medium of language. Therefore, it is a certainty that natural selection would operate to create a UG that was optimized to allow a child to acquire his or her native language in the same time frame as adult lactose tolerance, high-altitude adaptation, resistance to diseases, and so on, if UG really existed. That would result in observable differences in the ability of children “acquiring” English if their ancestors spoke a language other than English for thousands of years.
Optimality Theory (OT) was proposed by linguists of Chomskian persuasion to account for how children “acquire” the phonetic structure and phonology of their native language. OT posits an innate set of principles and parameters similar to the UG, the hypothetical store of information preloaded into every human’s brain necessary for a child to acquire the syntax of his or her native language. Through a process described using opaque linguistic jargon, a child activates the sounds and syllable structures that occur in the language that they hear. The store of “knowledge of language” in OT is supposedly absolutely necessary for a child to acquire her or his native language.
“Native” languages are subject to rapid change when people move. My father’s native languages were Polish and Yiddish. I have command of a few Yiddish words and phrases (mostly terms describing fools and a few other phrases) and no Polish whatsoever, so Noam Chomsky could argue that my ancestors had not lived long enough in one place to have formed language organs that optimized their acquiring either Yiddish or Polish. However, that does not hold for the Chinese emigrants who arrived in California in large numbers in the nineteenth century, or any other persons of Chinese ancestry. Chinese has an attested time depth of thousands of years. The most precious holding in the National Palace Museum in Taipei is a large bronze vase bearing written inscriptions dating back to 1000 BCE. Earlier inscriptions on bones date back to 4000 BCE.
Chinese were speaking Chinese long before cattle were introduced into Kenya. If the principles and parameters of genetically specified OT were actually necessary for children to acquire Chinese, natural selection would have acted on these principles and parameters. A selective sweep or successive selective sweeps acting on the gene or genes that code OT would have yielded OT Chinese, enhancing the ability of Chinese children to “acquire” Chinese. However, the sound pattern, syllable structure, and syntax of Chinese differs markedly from that of English. Mandarin Chinese syllables, for example, all have the form consonant-vowel (CV), except for syllables that end with a nasalized consonant such as [m] or [n]. If Chinese children actually had a built in “knowledge of language” that restricted them from forming anything other than these CV syllables, they would end up being unable to say “cat” or “basket,” or anything that deviated from their preloaded Chinese OT. If your parents, their parents, and so forth had lived in Iceland, where Old Norse has been preserved for 1,000 years, you would have similar problems.
When I presented this argument to a well-known MIT-trained linguist, his response was that perhaps students of Chinese ancestry at the Ivy League university where he taught did in fact have inherent difficulties “acquiring” English. I suggested that he assess the English-language proficiency of his students having Chinese ancestors. I haven’t since heard anything from him.
Back to Rube Goldberg
But first, let’s return to Rube Goldberg. I sometimes wonder whether some of the pundits who focus on Darwin’s shortcomings ever read On the Origin of Species. They point out the fact that natural selection cannot account for the abrupt transitions that clearly occurred in the course of evolution. However, Darwin accounted for these abrupt transitions in 1859.
Darwin noted that natural selection can act only by taking advantage of slight successive variations; “she can never take a leap, but most advance by the shortest and slowest steps” (Darwin, 1859, p. 194). Moreover, the variations that are favored are ones that advance the survival of progeny in a particular ecosystem. The term “ecosystem” serves nicely to convey the “infinitely complex relations to other organic beings and to external nature,” that to Darwin determined the selective pressures driving natural selection.
Changes in ecosystems are driven by external forces, changes in weather patterns, migrations, and so on. When an ecosystem abruptly changes, species ruled by their genes may not be able to adapt and become extinct. Most of the species that ever existed on earth are extinct; dinosaurs are only one example. But in other instances, evolution has created new species from existing ones to exploit totally new ecosystems. Everyone “knows” that fish cannot live out of water, but on the voyage of the Beagle around South America, Darwin observed lungfish—transitional creatures—that explained the puzzle. Deep into On the Origin of Species, Darwin notes that an
organ might be modified for some other and quite distinct purpose. . . . The illustration of the swimbladder in fishes is a good one, because it shows us . . . that an organ originally constructed for one purpose, namely flotation, may be converted into one for a wholly different purpose, namely respiration (Darwin, 1859, p. 190).
The lungfish swimbladder-to-lung “conversion” explains why our respiratory system is as whacky as any of Rube Goldberg’s machines. We have two elastic lung sacks that are inflated indirectly. Our inflated lungs increase the mass of water that we would displace if we were fish. If you were a sort of super-goldfish, this maneuver would allow you to hover almost effortlessly in a giant fishbowl. There is no direct connection between your lungs and any of the muscles that inflate the two sacks that take in air as we breathe. Instead, there is a sealed space, the pleural cavity that encloses the elastic lung sacks. Muscles in your abdomen and chest act to increase the volume of your body. This indirectly causes the lung sacks to expand, lowering air pressure in them so that atmospheric air at a higher pressure flows into them, enabling you to breathe in. The elasticity of the two lung sacks then forces air out when the inspiratory muscles relax during expiration.
You can perform the following experiment if you have a long bathtub and sharp vision. Fill your bathtub with soothing water. Then get into it, fully immersed, keeping only your head and one arm above water. Breathe in and carefully mark the water level. Breathe out, and you may be able to see the water level lower, reflecting the fishlike original function of your lungs, which was to displace water. The system makes total sense if you are a fish—increasing the volume of displaced water can enable an advanced fish to match the buoyancy of water at a specific depth, floating effortlessly. Less advanced fish such as sharks have to move constantly.
Stephen Jay Gould and Richard Lewontin reaffirmed Darwin’s views in their much-cited 1979 essay, “The Spandrels of San Marco and the Panglossian Program. A Critique of the Adaptationist Programme.” The provocative reference to Pangloss refers to Dr. Pangloss, the professor of “métaphysico-théologo-cosmolonigologie” who epitomizes mindless optimism in Voltaire’s satiric novel Candide. Dr. Pangloss viewed the string of horrific events in Candide (based on events of the Seven Years’ War and the 1755 Lisbon earthquake) as evidence that “all is for the best in the best of all possible worlds.” Pangloss was mouthing the optimistic worldview of the eighteenth-century German philosopher and mathematician Gottfried Wilhelm Leibnitz [1765] (1916).
The spandrels of San Marco are an architectural feature that the master-masons and architects of Europe invented to build cathedrals that had soaring, open inner spaces. Through trial and error, features like external flying buttresses and internal arches were invented to prevent these huge stone buildings from collapsing. San Marco has internal arches whose apexes support the upper part of the cathedral’s stonework. Similar arches in reinforced concrete support highway bridges today. The apex at the midpoint of the curving arch supports the roadway. In San Marco, the spaces between the arch and the sides of the building were filled in with stonework and decorated. The decorative stonework that filled in the spandrel thus was a by-product of the arch that was built for another purpose, keeping San Marco from tumbling down into a heap of large stones. The contribution to “fitness” (the selective advantage) of the spandrels wasn’t to enhance the display of statuary and bas-reliefs; it was to keep San Marco from falling down. The decorative stonework thus didn’t serve an “adaptionist” goal, through you could argue that art had value to the architects. Gould and Lewontin correctly pointed out that similar processes accounted for many of the features that we see in animals and plants.
Liebnitz was a setup for satire; his views on the meaning of words, which lives on in present-day “formal” linguistics, was skewered by Jonathan Swift in Gulliver’s Travels. We’ll return to that issue in chapter 4.
The roots of Jerry Fodor and Massimo Piatelli-Palmarini’s book What Darwin Got Wrong seem to go back to their misreading Stephen J. Gould’s subsequent 1985 essay, “Not Necessarily a Wing,” which presented a biological example that again reaffirmed Darwinian theory. The issue that Gould addressed in his essay was the evolution of butterfly wings. Early butterflies had very small wings that served as heat-transfer devices for thermal regulation. The wings gradually became larger to enhance the efficiency of thermal regulation, but still were too small to enable them to fly. Therefore, natural selection aimed at allowing butterflies to fly by gradually increasing the size of their wings could not account for why butterflies can fly. Gould’s answer was that wings gradually became larger and larger, and at some point the enlarged wings suddenly enabled butterflies to fly. Gould took care to point out that it was an example of the process that Darwin had pointed out in 1859, “an organ converted into one for a wholly different purpose.” Ernst Mayr had used the term “preadaptation” to refer to this process, Gould preferred the term “exaptation.”
From Motor Control to Cognition
The message of Theodosius Dobzhansky’s 1973 article “Nothing in Biology Makes Sense Except in the Light Of Evolution” should now be clear. It speaks to the evolution of the cortical-basal ganglia circuits that regulate cognitive processes. Dobzhansky played a key role in twentieth-century evolutionary biology, integrating Darwinian principles with emerging genetic knowledge. Dobzhansky and his colleague Ernst Mayr (1982) pointed out the odd, seemingly inexplicable aspects of biology that made no “sense,” but reflected the opportunistic nature of Darwinian evolution. It would be more “logical” and “simpler” to have a brain designed by IBM, Apple, Dell, Sony, Lenovo, and the like. As chapter 1 noted, we then would have a brain in which independent modules designed to efficiently carry out distinct tasks would each regulate some aspect of human behavior.
However, if that were so, the recurring pattern of motor, cognitive, and emotional deficits associated with aphasia, Parkinson disease, basal ganglia lesions, oxygen deficits, and other conditions would be inexplicable. Questions such as why brain damage that results in motor control problems also results in difficulty comprehending the meaning of English sentences would remain unanswered. What would motor control have to do with having difficulty understanding who kissed whom when you hear or read the sentence, “Susan was kissed by Tom”? Why do the basal ganglia, as Marsden and Obeso observed, carry out similar operations in motor and cognitive acts? The answers to these questions are clear once we realize that the neural bases of human cognition, including language, evolved by the Darwinian process by which an “organ might be modified for some other and quite distinct purpose.”
The Syntax of Motor Control, Whether It’s a Milling Machine or Walking
When I was an undergraduate at MIT, vacuum tubes, hot glowing globes, were the engines of all electronic devices. My classmates studying electrical engineering (MIT Course VI) and I designed and built our own hi-fi systems in our dorm rooms. The smell of solder smoldering on soldering irons was pervasive. We bought bags of World War II surplus vacuum tubes at the Radio Shack in downtown Boston. There was only one Radio Shack store then, and it was a vast jumble of electronic parts. The vacuum tubes performed very different local operations in the amplifiers and FM radios that we built. The tall 6L6s tubes were the output stages that drove our loudspeakers. The 6SN7 tubes amplified weak electrical signals that drove the 6L6s. Vacuum tubes would soon go the way of the dinosaurs, replaced by transistors that rapidly shrunk down to microscopic sizes in the integrated circuits that made the digital age possible.
While we were putting together these homemade music systems, computer-controlled machine tools were being developed in MIT’s laboratories and engineering workshops. My classmates’ master’s and ScD theses were at the cutting edge of a technological revolution that changed the world. Computer control was more precise than the most accomplished machinists could achieve. When I enrolled in MIT’s graduate linguistics program a few years later, my engineering friends pointed out that the sole difference between the syntax of the computer programs that ran milling machines and linguistic descriptions of sentence structure was that the milling machines had to work.
The demands placed on syntax do not substantially vary whether the task involves running a milling machine, walking, sentence structure, or any form of serial behavior. Karl Lashley, one of the pioneers of neuroscience, pointed this out:
Temporal integration is not found exclusively in language; the coordination of leg movements in insects, the song of birds, the control of trotting and pacing in a gaited horse, the rat running the maze, the architect designing a house, and the carpenter sawing a board present a problem of sequences of action . . . each of which similarly requires syntactic organization (Lashley, 1951, p. 113).
Walking, for example, involves positioning your foot to achieve heel strike at the precise moment of contact, whether you are on smooth pavement or the irregular surface of a country path. Your heel must flex at the proper moment, and that moment is different depending on whether you are on an incline, your posture, and your speed. Many linguists mistakenly think that the rules of syntax that, for example, govern word placement in an English sentence differ from motor control because their linguistic rules involve “selectional constraints.” The linguistic jargon term “selectional constraints” simply means that the rules have to be applied in a certain order. That clearly is also the case for the sequence of “rules” that governs walking. You cannot flex your foot to achieve heel strike before your foot is about to hit the ground. And if you are running, a different set of motor control rules and selectional constraints comes into play. As Marsden and Obeso (1994) presciently observed, the “rules” that the basal ganglia execute during motor control are not different from those necessary to describe cognitive processes. An organ that we share with frogs has been adapted to serve new ends.
Other Reshaped “Organs”: Three Little Bones
“A very large snake is eating my boyfriend on the arm.” It probably was the strangest call that the 911 operator in Putnam, Connecticut, had ever heard. Karen Ziner in the Providence Journal-Bulletin (October 14, 1998) reported the bizarre event. Christopher Paquin’s 19-foot, 260-pound pet python had twisted her coils around him, pinning him to the floor of his knotty-pine paneled sunroom. The snake opened its hinged jaw wide and swallowed his arm. Paquin called for help; his girlfriend, Tammy Breton, tried to pull the snake off using visegrip pliers, but Paquin yelled that she was hurting the snake. And so she dialed 911. When the police arrived, they found Paquin “being devoured all the way close to the shoulder.” Three policemen managed to separate Paquin from his pet. The snake was duly dispatched.
Paquin’s pet snake was able to engulf his arm because snakes have jaws that are connected by three hinge bones that enable them to dramatically open their jaws wide. There are other instances of pet pythons eating their owners and small children. You can find three similar bones in your middle ear. Resized and reshaped, they serve as a mechanical sound-amplifying system in all mammals. Mammals also possess the paleocortex (old cortex) that also differentiates mammals from reptiles. The paleocortex includes the anterior cingulate cortex (ACC). As chapter 1 noted, the anterior cingulate cortex plays a role in directing attention to virtually anything that you wish to do. The ACC dates back to Therapsids, mammal-like reptiles who lived in the age when dinosaurs roamed the earth.
The soft tissue of the brain obviously hasn’t survived 260 million years, and the inference that Therapsids had an ACC is based on their fossil remains having the three middle ear bones found in all present-day mammals. The initial function of the hinge bones of the reptilian jaw was to open the jaw wide. In the course of evolution, the hinge bones took on a dual role, also functioning as “organs” of hearing. The final mammalian transition involved the former jaw bones migrating into the middle ear, where they serve as a mechanical amplifier, increasing auditory acuity. In the Darwinian “struggle for existence,” being better able to hear her babies enhances the possibility of a mother keeping in contact with her suckling infants. This fits in with mammals having a paleocortex. Lesion studies show that the ACC’s role in a mouse mother is to get her to pay attention to her pups. Mouse mothers don’t pay attention to their infants when neural circuits involving the ACC are disrupted (Maclean and Newman, 1982; Newman, 1985). Similar, but more general, problems in maintaining attention occur when ACC to basal neural circuits are degraded in humans. Patients become apathetic, they don’t attend to events in the flow of life when the ACC to basal ganglia circuit is degraded (Cummings, 1993).
Evolutionary tinkering in the best tradition of Rube Goldberg converted the ACC’s role in maintaining a Therapsid or mouse mother’s attention to her infants to directing attention to anything. Virtually every PET or fMRI neuroimaging study ever published shows ACC activity when the subjects are asked to perform any task. Another reminder of Rube Goldberg engineering and our reptilian heritage is that you may develop an earache because you grind your jaws as you sleep. We retain the “old” nerve pathways between the jaw and the bones that have migrated into the middle ear.
The ACC has another role in mice and presumably Therapsids that enhances mother-infant interaction. The ACC controls the laryngeal “mammalian isolation cry”—the cry that keeps parents awake for months after a baby is born. It is part of a neural circuit involving the basal ganglia. In human adults, that circuit continues to be involved in laryngeal control. “Hypophonation,” exceedingly quiet speech from laryngeal dysfunction, is a sign of Parkinson disease, which degrades basal ganglia activity (Jellinger, 1990). As noted earlier, Parkinson disease also can result in speech production errors involving coordinating laryngeal, lung, tongue, and lip activity (Lieberman et al., 1992). The large bilateral basal ganglia lesions of patient CM, who was studied by Emily Pickett and her colleagues, resulted in highly aberrant laryngeal control. Phonation erratically occurred in consonants that should not have been phonated, indicating serious problems in laryngeal muscle control (Pickett et al., 1998). The afflicted members of the KE family whose basal ganglia development was affected by a broken FOXP2 gene also have speech production errors.
The inference drawn between anatomy and brains—the former hinge bones of reptiles and the anterior cingulate cortex—thus allows us to trace the evolution of one of the neural capacities that allow us to talk back to Therapsids.
The opportunistic fish-based evolutionary process that accounts for our lungs also affects the way that we talk and sing (or for coyotes and wolves, howl). It necessitates complex planning when we talk or sing because the alveolar (lung) air pressure would start out very high and then fall as the two elastic lung sacks deflate. This is the case during quiet respiration; the energy that pushes air out of your lungs during expiration has been stored in the elastic lung sacks. The elastic lung sacks act as springs, exerting maximum pressure when distended that gradually falls. It’s as though you blew up a balloon and then let go. The balloon would start by flying around fast, then slow down, and finally fall to the ground as it deflated.
If we didn’t act to modulate the alveolar air pressure pattern that occurs during quiet respiration, talking and singing would be impossible. That’s because the rate at which the vocal cords of the larynx move, which determines the fundamental frequency of phonation (F0), the perceived pitch of your voice, depends on the alveolar air pressure. When you intend to speak a long sentence or sing a long musical phrase, you have to take lots of air into your lungs before you utter a word, distending the elastic lung sacks. If you did nothing, the alveolar air pressure would be so high at the start of the sentence that your vocal cords would just be blown apart, producing a raspy sound. As you continued to talk, the alveolar air pressure would fall and the pitch of your voice would fall precipitously. What you must do instead before you utter a word is “program” a muscle command function that starts by maximally opposing (holding back) the elastic lung sack spring force and that gradually falls to match the falling lung sack elastic force, to achieve a level alveolar air pressure. The elastic lung sack hold-back function depends on the length of the sentence that you intend to say.
Weird and complicated? It’s the result of evolutionary tinkering with swim bladders to “make” lungs.