Brilliant Blunders: From Darwin to Einstein - Colossal Mistakes by Great Scientists That Changed Our Understanding of Life and the Universe (3 page)

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 “designer” (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.

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.”