by Livio, Mario
I have organized the book in such a way that for each scientist, I first present the essence of some of the theories for which this individual is best known. These are very concise summaries intended to provide an introduction to the ideas of these masters and an appropriate context for the blunders, rather than to represent comprehensive descriptions of the respective theories. I have also chosen to concentrate only on one major blunder in each case instead of reviewing a laundry list of every possible mistake that these pundits may have committed during their long careers. I shall start with the man about whom the New York Times correctly wrote in its obituary notice (published on April 21, 1882) that he “has been read much, but talked about more.”
CHAPTER 2
THE ORIGIN
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
—CHARLES DARWIN
The most striking thing about life on Earth is its prodigious diversity. Take a casual stroll on a spring afternoon; you are likely to encounter several kinds of birds, many insects, perhaps a squirrel, a few people (some may be walking their dogs), and a large variety of plants. Even just in terms of the properties that are the easiest to discern, organisms on Earth differ in size, color, shape, habitat, food, and capabilities. On one hand, there are bacteria that are less than one hundred thousandth of an inch in length, and on the other, there are blue whales more than 100 feet long. Among the thousands of known species of the marine mollusks known as nudibranchs, there are many that are plain looking, while others have some of the most sumptuous colors exhibited by any creature on Earth. Birds can fly at astonishing heights in the atmosphere: On November 29, 1975, a large vulture was sucked into a jet engine at a height of 37,900 feet above the Ivory Coast in West Africa. Other birds, such as the migrating bar-headed geese and the whooper swans, regularly fly higher than 25,000 feet. Not to be outdone, ocean creatures achieve similar records in depth. On January 23, 1960, the record-setting explorer Jacques Piccard and Lieutenant Don Walsh of the US Navy descended slowly in a special probe called a bathyscaphe to the deepest point at the bottom of the Pacific Ocean—the Mariana Trench—south of Guam. When they finally touched down at the record depth of about 35,800 feet, they were amazed to discover around them a new type of bottom-dwelling shrimp that did not seem to be bothered by the ambient pressure of some 17,000 pounds per square inch. On March 26, 2012, film director James Cameron reached the deepest point in the Mariana Trench in a specially designed submersible. He described it as a gelatinous landscape as desolate as the Moon. But he also reported seeing tiny shrimp-like critters no bigger than an inch in length.
Nobody knows for sure how many species are currently living on Earth. A recent catalogue, published in September 2009, formally describes and gives official names to about 1.9 million species. However, since most living species are microorganisms or very tiny invertebrates, many of which are very difficult to access, most estimates of the total number of species are little more than educated guesses. Generally, estimates range from 5 million to about 100 million different species, although a figure of 5 to 10 million is considered probable. (The most recent study predicts about 8.7 million.) This large uncertainty is not at all surprising once we realize that just one tablespoon of dirt beneath our feet could harbor many thousands of bacterial species.
The second amazing thing characterizing life on Earth, besides its diversity, is the incredible degree of adaptation that both plants and animals exhibit. From the anteater’s tubelike snout, or the chameleon’s long and fast-moving tongue (capable of hitting its prey in about 30 thousandths of a second!), to the woodpecker’s powerful, characteristically shaped beak, and the lens of the eye of a fish, living organisms appear to be perfectly fashioned for the requirements that life imposes on them. Not only are bees constructed so that they can comfortably fit into the flowering plants from which they extract nectar, but the plants themselves exploit the visits of these bees for their own propagation by polluting the bees’ bodies and legs with pollen, which is then transported to other flowers.
There are many different biological species that live in an astonishing “scratch my back and I will scratch yours” interaction, or symbiosis. The ocellaris clown fish, for instance, dwells among the stinging tentacles of the Ritteri sea anemone. The tentacles protect the clown fish from its predators, and the fish returns the favor by shielding the anemone from other fish that feed on anemones. The special mucus on the clown fish’s body safeguards it from the poisonous tentacles of its host, further perfecting this harmonious adaptation. Partnerships have even developed between bacteria and animals. For example, at seafloor hydrothermal vents, mussels bathed in hydrogen-rich fluids were found to thrive by both supporting and harvesting an internal population of hydrogen-consuming bacteria. Similarly, a bacterium from the genus Rickettsia was found to ensure survival advantages for the sweet potato whiteflies—and thereby for itself.
Parenthetically, one quite popular example of an astonishing symbiotic relationship is probably no more than a myth. Many texts describe the reciprocation between the Nile crocodile and a small bird known as the Egyptian plover. According to Greek philosopher Aristotle, when the crocodile yawns, the little bird “flies into its mouth and cleans his teeth”—with the plover thereby getting its food—while the crocodile “gets ease and comfort.” A similar description appears also in the influential Natural History by the first-century natural philosopher Pliny the Elder. However, there are absolutely no accounts of this symbiosis in the modern scientific literature, nor is there any photographic record that documents such a behavior. Maybe we shouldn’t be too surprised, given the rather questionable record of Pliny the Elder: Many of his scientific claims turned out to be false!
The prolific diversity, coupled with the intricate fitting together and adaptation of a wondrous wealth of life-forms, convinced many natural theologians, from Thomas Aquinas in the thirteenth century to William Paley in the eighteenth, that life on Earth required the crafting hand of a supreme architect. Such ideas appeared even as early as the first century BCE. The famous Roman orator Marcus Tullius Cicero argued that the natural world had to stem from some divine “reason”:
If all the parts of the universe have been so appointed that they could neither be better adapted for use nor be made more beautiful in appearance . . . If, then, nature’s attainments transcend those achieved by human design, and if human skill achieves nothing without the application of reason, we must grant that nature too is not devoid of reason.
Cicero was also the first to invoke the clock-maker metaphor that later became the touchstone argument in favor of an “intelligent designer.” In Cicero’s words:
It can surely not be right to acknowledge as a work of art a statue or a painted picture, or to be convinced from distant observations of a ship’s course that its progress is controlled by reason and human skills or upon examination of the design of a sundial or a water-clock to appreciate that calculation of the time of day is made by skill and not by chance, yet none the less to consider that the universe is devoid of purpose and reason, though it embraces those very skills, and the craftsmen who wield them, and all else beside.
This was precisely the line of reasoning adopted by William Paley almost two millennia later: A contrivance implies a contriver, just as a design implies a designer. An intricate watch, Paley contended, attests to the existence of a watchmaker. Therefore, shouldn’t we conclude the same about something as exquisite as life? After all, “Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater and more, and that in a degree which exceeds all computation.” This fervent pleading for the imperative need for a “des
igner” (since the only possible but unacceptable alternative was considered to be fortuitousness or chance) convinced many natural philosophers until roughly the beginning of the nineteenth century.
Implicit in the design argument was yet another dogma: Species were believed to be absolutely immutable. The idea of eternal existence had its roots in a long chain of convictions about other entities that were considered enduring and unchanging. In the Aristotelian tradition, for instance, the sphere of the fixed stars was assumed to be totally inviolable. Only in Galileo’s time was this particular notion completely shattered with the discovery of “new” stars (which were actually supernovae—exploding old stars). The impressive advances in physics and chemistry during the seventeenth and eighteenth centuries did point out, however, that some essences were indeed more basic and more permanent than others, and that a few were almost timeless for many practical purposes. For example, it was realized that chemical elements such as oxygen and carbon were constant (at least throughout human history) in their basic properties—the oxygen breathed by Julius Caesar was identical to that exhaled by Isaac Newton. Similarly, the laws of motion and of gravity formulated by Newton applied everywhere, from falling apples to the orbits of planets, and appeared to be positively unchangeable. However, in the absence of any clear guidelines as to how to determine which natural quantities or concepts were genuinely fundamental and which were not (in spite of some valiant efforts by empiricist philosophers such as John Locke, George Berkeley, and David Hume), many of the eighteenth-century naturalists opted to simply adopt the ancient Greek view of ideal, unchanged species.
Figure 1
These were the prevailing tides and currents of thought about life, until one man had the chutzpah, the vision, and the deep insights to weave together a huge set of separate clues into one magnificent tapestry. This man was Charles Darwin (figure 1 shows him late in life), and his grand unified conception has become humankind’s most inspiring nonmathematical theory. Darwin has literally transformed the ideas on life on Earth from a myth into a science.
Revolution
The first edition of Darwin’s book On the Origin of Species was published on November 24, 1859, in London, and biology was changed forever on that day. (Figure 2 shows the title page of the first edition; Darwin referred to it as “my child” upon publication.) Before we examine the central arguments of The Origin, however, it is important to understand what is not discussed in that book. Darwin does not say even one word either about the actual origin of life or about the evolution of the universe as a whole. Furthermore, contrary to some popular beliefs, he also does not discuss at all the evolution of humans, except in one prophetic, optimistic paragraph near the end of the book, where he says, “In the distant future I see open fields for more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by graduation. Light will be thrown on the origin of man and his history.” Only in a later book, The Descent of Man and Selection in Relation to Sex, which was published about a dozen years after The Origin, did Darwin decide to make it clear that he believed that his ideas on evolution should also apply to humans. He was actually much more specific than that, concluding that humans were the natural descendants of apelike creatures that probably lived in trees in the “Old World” (Africa):
We thus learn that man is descended from a hairy, tailed quadruped, probably arboreal in its habits and an inhabitant of the Old World. This creature, if its whole structure had been examined by a naturalist, would have been classed among the Quadrumana [primates with four hands, such as apes], as surely as the still more ancient progenitor of the Old and New World monkeys.
Figure 2
Most of the intellectual heavy lifting on evolution, however, had already been achieved in The Origin. In one blow, Darwin disposed of the notion of design, dispelled the idea that species are eternal and immutable, and proposed a mechanism by which adaptation and diversity could be accomplished.
In simple terms, Darwin’s theory consists of four main pillars that are supported by one remarkable mechanism. The pillars are: evolution, gradualism, common descent, and speciation. The crucial mechanism that drives it all and glues the different elements into cooperation is natural selection, which, we know today, is supplemented to some degree by a few other vehicles of evolutionary change, some of which could not have been known to Darwin.
Here is a very succinct account of these distinct components of Darwin’s theory. The description will mostly trace Darwin’s own ideas rather than updated, modernized versions of these concepts. Still, in a few places, it will be essentially impossible to avoid the delineation of evidence that has accumulated since Darwin’s time. As we shall discover in the next chapter, however, Darwin did make one serious error that could have negated entirely his most important insight: that of natural selection. The root of the error was not Darwin’s fault—nobody in the nineteenth century understood genetics—but Darwin did not realize that the theory of genetics with which he was operating was lethal for the concept of natural selection.
The first essence in the theory was that of evolution itself. Even though some of Darwin’s ideas on evolution had an older pedigree, the French and English naturalists that preceded him (among whom, figures such as Pierre-Louis Moreau de Maupertuis, Jean-Baptiste Lamarck, Robert Chambers, and Darwin’s own grandfather, Erasmus Darwin, stood out) failed to provide a convincing mechanism for evolution to take place. Here is how Darwin himself described evolution: “The view which most naturalists entertain, and which I formerly entertained—namely, that each species has been independently created—is erroneous. I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species.” In other words, the species that we encounter today did not always exist. Rather, these are the descendants of some earlier species that became extinct. Modern biologists tend to distinguish between microevolution and macroevolution. Microevolution encompasses small changes (such as those sometimes observed in bacteria) that are the results of the evolutionary process over relatively short periods of time, typically within local populations. Macroevolution refers to the results of evolution over long timescales, typically among species—and which could also involve mass extinction episodes, such as the one that snuffed out the dinosaurs. In the years since the publication of The Origin, the idea of evolution has become so much the guiding principle of all the research in the life sciences that in 1973 Theodosius Dobzhansky, one of the twentieth century’s most eminent evolutionary biologists, published an essay entitled “Nothing in Biology Makes Sense Except in the Light of Evolution.” At the end of this article, Dobzhansky noted that the twentieth-century French philosopher and Jesuit priest Pierre Teilhard de Chardin “was a creationist, but one who understood that the Creation is realized in this world by means of evolution.”
Darwin borrowed the idea embodied in his second pillar, that of gradualism, mainly from the works of two geologists. One was the eighteenth-century geologist James Hutton, and the other was Darwin’s contemporary and later close friend Charles Lyell. The geological record showed horizontal banding patterns covering large geographical areas. This, coupled with the uncovering of different fossils within these bands, suggested a progression of incremental change. Hutton and Lyle were largely responsible for the formulation of the modern theory of uniformitarianism: the notion that the rates at which processes such as erosion and sedimentation occur at present are similar to the rates in the past. (We shall return to this concept in chapter 4, when we’ll discuss Lord Kelvin.) Darwin argued that just as geological action shapes the Earth gradually but surely, evolutionary changes are the result of transformations that span hundreds of thousands of generations. One should not, therefore, expect to see significant alterations in less than tens of thousands of years, except perhaps in organisms that multiply very frequently, such as bacteria, wh
ich, as we know today, can develop resistance to antibiotics in extremely short times. Contrary to uniformitarianism, however, the rate of evolutionary changes is generally nonuniform in time for a given species, and it can vary further from one species to another. As we shall see later, it is the pressure exerted by natural selection that determines primarily how fast evolution manifests itself. Some “living fossils” such as the lamprey—a jawless marine vertebrate with a funnel-like mouth—appear to have hardly evolved in 360 million years. As a fascinating aside, I should note that the idea of gradual change was put forth in the seventeenth century by the empiricist philosopher John Locke, who wrote insightfully, “The boundaries of the species, whereby men sort them, are made by men.”
The next pillar in Darwin’s theory, the concept of a common ancestor, is what has become in its modern incarnation the primary motivator for all of the present-day searches for the origin of life. Darwin first argued that there is no doubt that all the members of any taxonomic class—such as all vertebrates—originated from a common ancestor. But his imagination carried him much further with this concept. Even though his theory predated any knowledge of the facts that all living organisms share such characteristics as the DNA molecule, a small number of amino acids, and the molecule that serves as the currency for energy production, Darwin was still bold enough to proclaim, “Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype.” Then, after cautiously acknowledging that “analogy may be a deceitful guide,” he still concluded that “probably all the organic beings which have ever lived on the earth have descended from some one primordial form, into which life was first breathed.”