Purpose and Desire Read online

  The conventional history of the rise of Darwinism—there’s always a conventional history—tells a similar tale, of a bright spring, full of promise, emerging from a long, dark winter. Here is how one historian of Darwinism, Michael Ghiselin, pithily describes it:

  [Darwin’s theory of evolution] focused attention on the principle of natural selection, which a lot of people did not like. Some of the people were French, and their attitudes were colored by chauvinism. They wanted an explanatory principle devised by a Frenchman. Others rejected natural selection because they did not like the relentlessly competitive world that selection implied and that Darwin envisioned. They wanted something that would be more in keeping with their personal, beneficent political values. For these and other reasons, people espoused various alternatives to natural selection, and a number of factions were formed.

  By the beginning of the 1900s, two of the factions had gained major importance and were dominating the debate about evolution. One faction comprised people who favored natural selection as the chief mechanism of evolution, and who rejected the inheritance of acquired characteristics; these people came to be called “Neo-Darwinians.” The other group advocated a wide variety of evolutionary mechanisms (known or unknown), and they also accepted the premise that acquired traits could pass from one generation to the next; these people were called “Neo-Lamarckians.”

  The controversy between the two groups endured for several decades, but by 1940 biologists had learned so much about genetics and related subjects that the ideas of the “Neo-Lamarckians” were generally abandoned. They play no role in our modern theory of evolution, which emerged during the 1940s and the early 1950s.1

  And there you have it: before Darwin, and for some time after, evolutionism was haunted by the ghost of someone named Lamarck, motivated by morality, idealism, and French chauvinism. What’s worse, the Lamarckians were spirit-mongers, idealists who wanted to reinfect evolution with their discredited vitalist yearnings. They were doomed to lose to the Darwinists, who were the “real” scientists and who let facts, not wishes, speak with the loudest voice. Reason triumphed, and the crisis of Darwinism was solved.

  Figure 5.1

  Famous figures of the “French Evolution.” (left) Lamarck (1744–1829); (right) Cuvier (1769–1832).

  But what of this fellow Lamarck? By the early nineteenth century, so the story goes, the idea of evolution was “in the air,” put there by the evolutionary “speculations” of the French naturalist Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck, or as he is better known, simply Lamarck (Figure 5.1).* Despite seeing the reality of evolutionary change, Lamarck went wrong because he believed that evolution worked through the “inheritance of acquired characteristics.”2 To trot out a well-worn example, giraffes had long necks because their okapi-like ancestors had long been stretching their necks to reach high up into trees for tender foliage. The stretching “took,” and this is how the short-necked ancestors of giraffes came to be the long-necked giraffes of today.* When we tell this story to students today, it is usually accompanied by a good laugh at Lamarck’s expense: how silly an idea!

  Another Frenchman is lurking in the wings of Darwinism’s great saga. Following Lamarck was the great anatomist Georges Léopold Chrétien Frédéric Dagobert, Baron Cuvier, his name, again, and mercifully, condensed to Cuvier (see Figure 5.1). Cuvier is supposed to have reconciled his essentially creationist bent with the record told by fossils, the “formed stones” that Cuvier had, by his own hand, organized and crafted into what we now call the “fossil record.” The story told by that fossil record challenged the origin story told in Genesis. There seems to have been not one creation, but many, each one different from the last. The history of life on Earth was marked by long periods during which animals and plants persisted unchanged, punctuated by episodes of catastrophic extinction, followed by proliferation of new species, when life settled into the next long period of stasis. According to Cuvier, we are living in the last of these serial creation events. Not only did this contradict the single creation of Genesis, it contradicted another dogma of the age, the conception of the unchanging species laid down by the great Carl Linnaeus (1707–1778). To Linnaeus, species were reflections of unchanging archetypes. The diverse starfishes, for example, were a reflection of an unchanging “starfishness” and so were unchanging themselves. The fossil record seemed to be saying otherwise: species changed, they had history, and they had beginnings and ends—quite radical ones at that.

  Both Lamarck and Cuvier are held up today as avatars of a benighted past, who almost got to the gold ring of the “right” answer to evolution, that is to say, Darwin’s answer, but were held back by self-imposed constraints of vitalism and religious obscurantism. Lamarck is often credited with making the idea of evolution respectable—putting evolutionism “in the air” that, like that first breath of spring air, Darwin would eventually inhale and bring to glorious fruition.* Cuvier, for his part, is credited with at least two of the important place settings that would come to adorn the Darwinian feast. The first was his challenge to the concept of the unchanging Linnaean species, hence the title of Darwin’s revolutionary book, On the Origin of Species. The second was the theory of homology, which is the tendency of parts of animals to change and take on different forms and functions.* Homology showed how lineages could transform from one form seamlessly into another: how a fish’s pectoral fins could transform into a frog’s forelimb, into a horse’s front hoof, into the wing of a bird, into the hand of someone playing Chopin. Homology gave Darwin the model he needed to show how new species could arise, not catastrophically, but gradually and imperceptibly through minute changes acting over many generations.

  Despite this, both Lamarck and Cuvier are held to have fallen short of the prize that Darwin claimed. Lamarck’s intellectual failure was twofold. First, he was fixated on something called the scala naturae, literally, the ladder of nature, which was the supposed progressive ratchet that led all life inexorably to greater and greater complexity and perfection, culminating, naturally, in humanity. Lamarck’s second failure was his obsession with an erroneous model of inheritance: the already-mentioned inheritance of acquired characteristics, of which more momentarily. For Cuvier’s part, he is supposed to have missed out on the gold ring by being a creationist and catastrophist.*

  Like the folk stories that have accreted around Claude Bernard, this conventional history is flawed, being less history than a narrative that keeps out some uncomfortable ideas.3 One uncomfortable idea is that both Lamarck and Cuvier are better understood in the context of scientific vitalism, not the vitalism of spooks and vital essences. This makes Lamarck and Cuvier more of a challenging proposition to the Darwinian narrative and not so easily dismissed with amusing stories of the long necks of giraffes. Even more uncomfortable is the light this shines on Darwin’s own thinking, which puts Lamarck, Cuvier, and Darwin into a coherent and seamless alternate narrative of evolutionary thought—one driven not by blind mechanism, but by purpose and desire, and marked not by the differences between the three men, but by their similarities.

  Both Lamarck and Cuvier rose from lowly beginnings to become giants of the French Enlightenment. Although they came to be bitter enemies, together they launched what we might call the French Evolution.* The relationship between the French Evolution and English evolutionary thought—perhaps we can call the latter the Glorious Evolution—was deep, complex, and like the revisionist history of Claude Bernard, built around a number of myths that we will have to sort through. One such myth is the caricature of Lamarck and Lamarckism as the bête noir of rational—that is, Darwinian—evolutionism. Cuvier’s creationist tendencies are a second. That Darwin rejected Lamarckism—got evolution “right”—is a third.4

  Lamarck was the scion of a family of aristocrats from northern France who had fallen on hard times. The young Lamarck first sought his fortune, as so many in Lamarck’s circumstances did, in military service to his king. At the young age
of seventeen, his bravery during a skirmish in the Pomeranian War* won him a pension from his grateful sovereign. This bought Lamarck sufficient leisure to pursue a burgeoning interest in natural history, focusing in particular on plants. Lamarck was also a social climber, and he eventually worked his way into the directorship of the Jardins du Roi in Paris (renamed the Jardins des Plantes in the revolution’s aftermath).

  Cuvier, for his part, was born into a French Protestant family from Montbéliard, near the German border of the Duchy of Württemberg. After concluding a brilliant student career, Cuvier found employment as a tutor in natural history to a Protestant nobleman in Normandy. There, Cuvier stumbled into what we would now call a networking opportunity. At that time, France was in the midst of its painful postrevolutionary upheaval, which made life in Paris very dangerous. While on a stroll one day, Cuvier had a chance encounter with the physician and agronomist Henri Tessier, who was living incognito in Normandy. Because Tessier had been a favorite of the deposed king, he naturally had feared being caught up in the Reign of Terror if he stayed in Paris. When Cuvier saw through his disguise, Tessier initially thought he was doomed, but Cuvier assured Tessier that he had no intention of exposing him. His secret (and life) secure, Tessier and Cuvier became fast friends. Once Tessier was confident that he could return to Paris and keep his head, he took Cuvier with him, introducing him into the burgeoning intellectual life of postrevolutionary Paris. Once there, Cuvier was able to leverage his connections and was asked to join the Académie des Sciences of the Institut de France. From his new Parisian base, Cuvier built his stellar career in paleontology.

  Lamarck was older and a more traditional thinker than Cuvier, and so Lamarck’s thinking was infused still with the search for essences and forces that could explain the organism’s, and life’s, unique properties of adaptability, coherence, and organization. Like his contemporaries, Lamarck’s thinking was influenced by the growing conception of the organism as “many little lives,” but he lived at a time when scientific vitalism had yet to outgrow its obsession with vital essences: the vis mediatrix, the vital stuff that coordinated it all, was still a viable idea. Lamarck therefore sought vital principles that could unify our understanding of the universe, from mineralogy to the weather to life itself, although he saw these more in terms of immaterial vital forces than vital matter. It’s tempting to look at Lamarck’s rather quaint essentialist ideas and summarily dismiss the rest of his thinking. Indeed, this was the very thing that Lamarck’s opponents (beginning with Cuvier) have done through the years, and to great effect. This is a pity, because it paints a caricature of Lamarck that obscures his truly revolutionary idea.

  Lamarck proposed that living systems are uniquely imbued with at least two vital forces. One is the pouvoir de la vie (life power), which is more accurately, if more cumbersomely, rendered in French as la force qui tend sans cesse à composer l’organisation (“the force that tends perpetually to make order,” or perpetual order-producing force). In English, we describe this more succinctly as the “complexifying force,” because it supposedly impelled living systems toward ever greater complexity. For individual organisms, the complexifying force is what drives, say, the transformation of a formless mass of yolk, semen, and egg into a complex living organism.

  Lamarck’s second vital force was the influence des circonstances, cast more simply as the “adaptive force.” Within the individual, adaptive force modifies the body to help it meet changing and unpredictable environmental circumstances. If fur becomes thicker in the winter, if skin becomes darker under the sun, if muscles become stronger under strain, this is the adaptive force at work. Both the complexifying and adaptive forces were the mainstays of the vitalist thinking of Lamarck’s day, and his thinking in this regard was not original with him. As we have just seen, Lamarck’s complexifying force was essentially drawn from the same philosophical well as the epigenetic force that was said to drive embryonic development from the formless egg into the complex organism.*

  Lamarck’s real intellectual innovation was to propose that these forces could apply to lineages of organisms as much as they applied to individual organisms (Figure 5.2). Not only were developing embryos, for instance, marked by an ever increasing complexity through time, the lineages of successive generations of embryos were as well. Thus, the complexifying force could act both across and within generations. Similarly, if the adaptive force could be invoked to fit an organism more aptly to a new set of circumstances, so too could the adaptive force operate over many generations to bring about an ever more apt fit of a lineage to, say, a long-standing change of environment. If burrowing shrews lost their eyes to become moles, if shrews grew wings to become bats, if panthers grew lithe and supple to become cheetahs, this was the adaptive force working across generations. Put them both together, and you have a theory of evolution: of lineages becoming ever more complex and ever more well-adapted through the lineage’s history.

  Figure 5.2

  A Lamarckian phylogeny. Complexity increases with time, owing to the continuous operation of the complexifying force. Each lineage in turn increases in complexity over time, owing to the same complexifying force.

  This puts Lamarck’s thought into a different perspective than our accustomed view of it: it is not a mish-mash of rather silly ideas about giraffes stretching their necks or sons of blacksmiths having stronger arms than their fathers. To the contrary, take away the essentialist gloss, and we see some rather modern thinking on Lamarck’s part. The complexifying force, for example, bears some similarity to the modern notion of spontaneous order emerging from open thermodynamic systems.5 Lamarck’s adaptive force, for its part, looks a lot like homeostasis, properly understood. The main point about Lamarck, though, is that his thinking was not, as the caricature would imply, centered on a wrong-headed theory of inheritance. Rather, he was proposing a radical connection between adaptation in individuals and adaptation in lineages. It was, for its time, a unified field theory of adaptation. This brings us to the reason why Lamarck has been the object of such caricature: his idea of a unified theory of adaptation is inconvenient to the modern narrative that physiological adaptation and evolutionary adaptation are completely separate things, as outlined in the last chapter. Lamarck begs to differ: they are one and the same.

  If Lamarck was the grand theorist of the French Evolution (or system-builder, as he was then contemptuously called), Cuvier was its law-giver. He is sometimes portrayed as an anti-evolutionist, but this is a canard. Of course Cuvier was an evolutionist: his paleontological work built the best case then extant that species changed through time. What Cuvier rejected was not evolution itself, but the idea that evolution was gradual or operated through mere mechanical processes. The evidence from the fossil record clearly showed that life changed abruptly, not gradually, as Lamarck’s model seemed to predict.

  Again, we see elements of some surprisingly modern thinking here. The doctrine of punctuated equilibrium, which had a burst of popularity in the 1980s, emphasized patterns in the fossil record that were very similar to Cuvier’s serial catastrophes: a species would persist unchanged for long periods, punctuated with bursts of rapid species proliferation. Punctuated equilibrium wasn’t quite Cuvier’s catastrophism, of course, but it affirmed Cuvier’s reading of the patterns of the fossil record.6 Catastrophism, meanwhile, had new life breathed into it with the growing realization in the 1970s that an asteroid collision with the Earth sixty-five million years ago may have hurried dinosaurs (and a lot of other creatures) off the stage.7 Now we look for evolutionary catastrophes everywhere, with intriguing but mixed results. There is, for example, the thought-provoking idea of Nemesis, the distant Death Star whose gravitational pull periodically flings asteroids toward Earth, raining down death and extinction like Zeus’s thunderbolts, revealed in the periodic waves of mass extinction that mark the fossil record.8 Or perhaps these are just statistical noise. Who knows? Cuvier’s catastrophes may have to be taken seriously after all, but that is
a task for another day.

  It is Cuvier’s work in comparative anatomy that is most of interest to us, because it was thoroughly steeped in the emerging doctrines of scientific vitalism and in the same “many little lives” metaphor that so strongly influenced Claude Bernard. Comparative anatomy compares the forms of different species with one another: how a horse’s hoof is like a mouse’s hand, for example. Comparative anatomy is something we force modern students of biology to endure because it teaches them valuable lessons about homology. Homology is important to the Darwinian idea because it bolsters the empirical case for the gradualist model of evolution that Darwin championed. To Cuvier, homology was something different entirely—a model for how lineages were resistant to change through time. For Cuvier, comparative anatomy provided the evidence for his own theory of adaptation, which he called the “conditions for existence.”9

  This is a term of some confusion, which must be cleared up. Darwin appropriated this phrase as a metaphor for the organism’s adaptive milieu, that is, adaptation to ambient conditions. But Cuvier coined the phrase to mean those conditions within an organism that would serve apt function. His logic went something like this: to survive and reproduce, an organism had to be objectively capable of surviving and reproducing; to do that, all the parts of the body had to work well together. These were Cuvier’s conditions for existence. If the parts did not work well together, the conditions for existence would not be met, and debilitation, death, and failure of the lineage would be the outcome.