Archetypes and Ancestors

Lamarck and Geoffroy had been friends at the museum for decades, but Geoffroy came to accept evolution through his own research, comparing the anatomy of different animals. The conventional wisdom of the day held that animals were similar to each other only when they functioned in similar ways. But Geoffroy was struck by exceptions to this supposed rule. Ostriches have the same bones as flying birds, even though they don’t fly. And Geoffroy showed that what looked like unique hallmarks that set off a species from other animals often were not so singular after all. A rhino’s horn might seem to make it unique, for example, but it is really just a clump of dense hair.

As Geoffroy struggled to uncover the hidden connections between animals, he found much inspiration in the work of German biologists. They saw science as a transcendentalist quest to discover the hidden unity of life. The poet (and scientist) Goethe argued that the various parts of a plant–from its petals to its thorns–were all variations on one fundamental form: the leaf. For these German biologists, the complexity of life hid certain timeless models, which they called archetypes. Geoffroy set out to find the archetype of all vertebrates.

Every bone in every vertebrate’s skeleton, Geoffroy suggested, was a variation on an archetypal vertebra. He then pushed his scheme even further, claiming that invertebrates were based on the same transcendental plan. A lobster and a duck, by his reasoning, were variations on the same theme. Lobsters are arthropods, a group that also includes insects, shrimp, and horseshoe crabs. Arthropods bear some faint resemblances to vertebrates: their bodies are symmetrical along their long axis; they have heads equipped with eyes and a mouth. But the differences are vast. Arthropods build their skeleton–a hard shell–on the outside of their bodies, whereas vertebrates put theirs on the inside. Vertebrates have a spinal cord running along their back and a digestive tract running down the front of their bodies. In a lobster, or any other arthropod, the arrangement is reversed: the gut runs down the back and the nervous system runs along the belly.

This might seem to make the arthropods and vertebrates incomparable, but not to Geoffroy. He claimed that arthropods lived inside a single vertebra. And it was a simple matter to transform belly to back, and thus turn a lobster into a duck. Arthropods had the same design as vertebrates, but it was simply turned upside down. “There is, philosophically speaking, only a single animal,” Geoffroy declared.

By the 1830s, Geoffroy had taken his theory a step further. These transformations weren’t simply geometrical abstractions, he declared; animals had in fact changed shape over time. Geoffroy was not reviving Lamarck; he didn’t accept Lamarck’s hypothesis that a trait acquired during an animal’s life could be passed down to its offspring. Geoffroy suggested instead that a change in an animal’s environment might disturb the way it developed from an egg. Freaks would be born, and would become a new species.

You could see the history of this evolution, Geoffroy claimed, if you looked at how embryos develop today. German scientists were discovering how embryos changed in a matter of days from one bizarre form to another, often bearing no resemblance to the adult forms of the animals. The researchers carefully catalogued their fleeting parts and shapes, and the longer they looked, the more order they claimed to see in the confusion. They were impressed in particular by the way an embryo began as a simple form and gradually grew more complex. They even claimed that each increasingly complex form added a new stage to its development.

Lorenz Oken, one of the German scientists, explained the process this way: “During its development, the animal passes through all stages of the animal kingdom, rising up as it takes on new organs. The foetus is a representation of all animal classes in time.” At first it was just a tube, like a worm. Then it developed a liver and a vascular system and became a mollusk. With a heart, and a penis, it became a snail. When it sprouted limbs, it became an insect. When it developed bones, it became a fish; muscles, a reptile; and so on, up to mankind. “Man is the summit, the crown of nature’s development,” Oken announced.

Geoffroy proposed that embryos didn’t just climb the scale of nature; they replayed history. The ancestors of humans really were fish, and the evidence that we sport gill slits at an early stage in our development proved it.

As Geoffroy argued for evolution, European explorers were discovering new species that he claimed fit in perfectly with his theory. The platypus of Australia, for example, was a mammal, but it had a ducklike bill and laid eggs, inspiring Geoffroy to call it a transitional form between mammals and reptiles. In Brazil explorers found lungfish that could breath air through lungs, representing a link between vertebrates in the ocean and on land.

In England, the leading scientists denounced Geoffroy just as they had denounced Lamarck. Adam Sedgwick, the devout Cambridge geologist, declared the work of the two Frenchmen to be “gross (and dare I say it, filthy) views of physiology.” But while British scientists generally abhorred evolution, the job of attacking it head‑on in the 1830s was left to one man: a brilliant young anatomist named Richard Owen.

Owen was often the first British anatomist to study new species such as the lungfish and the platypus, and he took these opportunities to strike down Geoffroy’s claims. Owen showed that platypuses actually secrete milk, a hallmark of mammals. And lungfish, while they might have lungs, didn’t appear to have nostrils, which all land vertebrates have. That, for Owen, was enough to relegate them to being ordinary fish.

Yet Owen himself was not content simply to say that God created life, and that its design reflected His goodness. Owen wanted to uncover the natural mechanisms of creation. He abhorred Geoffroy’s wild speculations on evolution, but he was too good a naturalist to deny that he was right about some things. The similarities between species, and the ways in which they could be arranged into a series of transformations, were too obvious to be denied.

Owen decided that Geoffroy had just lurched too far in his interpretation of the evidence. Owen knew, for example, that Geoffroy’s notions about how embryos formed had been supplanted by new research. A Prussian scientist named Karl von Baer had shown that life was not a simple ladder, with more advanced embryos recapitulating the development of more primitive ones. In the earliest stages of embryos, vertebrates did look like one another, but only because they were just a handful of cells. As time passed they grew more distinctive. Fishes, birds, reptiles, and mammals all have limbs, and they all initially form limb buds as embryos. But in time, those buds turn into fins, hands, hooves, wings, and the other kinds of limbs unique to certain kinds of vertebrates. One kind does not form from another. “A linear arrangement of animals in order of perfection,” von Baer wrote, “is impossible.”

Owen’s ambition was to tie together the work of von Baer, Geoffroy, and all the other great biologists of his day into one grand theory of life. He wanted to fight against evolution, but he wanted to do so by finding laws of nature that could account for the evidence of fossils and embryos.

He met Darwin for the first time three weeks after the Beagle’ s return. They both came to dinner at Lyell’s house, where Darwin regaled the party with his stories about the earthquake in Chile. After dinner, Lyell introduced the two young men (Owen was only five years older than Darwin). They got along well, and Darwin recognized in Owen someone famous enough to bring his fossil mammals to national attention. He asked Owen that night if he would examine them. Owen said that he would be happy to do so. They would give him a chance to test his ideas against fossils that no one had seen before.

He had no way of knowing that Darwin would one day render him a fossil as well.