The “Red Notebook” [5
] is the first of the series of notebooks in which Darwin established the essential elements of his evolutionary theory. Although apparently started while still on the Beagle
in 1836—recording various latitude, longitude, and depth soundings—the last third of the notebook seems to have been filled out after Darwin returned to England in late 1836, early 1837. Historians still disagree whether or not—or the degree to which—Darwin had tumbled to the idea of evolution while still on the Beagle
. I fully agree with Kohn et al. [6
] that the famous passage in his Ornithological Notes
, discussing the differentiation of “varieties” of mockingbirds and tortoises on various islands in the Galapagos and concluding that “if there is the slightest foundation for these remarks to zoology of Archipelagoes—will be well worth examining; for such facts would undermine the stability of Species” [7
] in fact does establish that Darwin was thinking about evolution in the final months before the Beagle
arrived home. But nothing else unambiguously written while still aboard ship has as yet turned up to support this view.
Darwin was a fully committed evolutionist by the time the evolutionary passages of the “Red Notebook” were written. As he would subsequently write in the topic sentence of the Origin of Species
, Darwin had been greatly struck by “certain facts of the distribution of the inhabitants of South America” that “throw some light on the origin of species.” [3
]. Elsewhere, Darwin makes clear that there were three distinct patterns of replacement of “allied” forms. First, the replacement of extinct species by modern ones—belonging to groups unique to that part of the world. For example, armadillos now live, while the obviously closely similar giant glyptodonts (which Darwin collected in Argentina) are now extinct. Both are edentate mammals—found only in the Americas. Second, in the living world, closely similar species tend to replace each other over broad expanses of mainland South America. The original example of this is the replacement of the common rhea (ostrich-like bird) by the lesser (Darwin's) rhea in more southerly stretches of South America. And third, the replacement by similar varieties or species of animals and plants on different islands (in the Galapagos especially—but he also mentions the two different forms of fox found on each of the two Falkland Islands). The mockingbirds and tortoises are early examples; as is well-known, Darwin did not himself see similar replacement patterns in finches, which later became known as “Darwin's finches,” and the equally riveting plant examples had to await expert analysis, forthcoming only after Darwin had been home for some time.
Darwin, famous for his views of gradual evolution through natural selection in the Origin of Species
, is unexpectedly a saltationist in the “Red Notebook.” He thinks, given the lack of intergradations between fossil forms, or his rheas, that new species must arise suddenly from ancestral species. He maintains this view to some degree in Notebook B, first of the four famous “Transmutation Notebooks” [8
], begun in the summer of 1837 and finished in early 1838. But with Notebook B, his attention turns to defining the first of three additional patterns, seeing these as expected observations if evolution is true. Darwin's initial three replacement patterns were inductive generations that took some while to dawn on his conscious mind. Now, with Notebook B he turns the tables and establishes the idea of evolution in a hypothetico-deductive framework.
There is grandeur in this view of life.
First of these new expected patterns is the nested set of taxa already recognized and embodied in Linnaeus's Systema Naturae
]. We now know why, in other words, there seems to be a natural classification of species—an explanation that differs from creationism precisely because it does make predictions about what we should expect to observe if evolution is true. In what is Darwin's closest equivalent to Einstein's handwritten E = MC2
, he writes (Notebook B, page 36) “I think,” [8
] and sketches an abstract evolutionary tree. He goes on to add embryological resemblance and “the unity of type” (homology), all close correlates of the “natural system”—all seen as predicted observations under the theory of transmutation (descent with modification eventually equals evolution).
But Darwin wanted more: he was constantly searching for a mechanism. Finally, in Notebook D, after having read Thomas Malthus and learned for the first time that more organisms are born to each species each generation than can possibly survive and reproduce (otherwise, “the world would be standing room only in elephants after but a few thousand years,” [3
] he wrote later in the Origin of Species
), he formulated “natural selection.” As David Kohn [10
] first pointed out, Darwin parses natural selection pithily on page 58 of Notebook E (1839): “Three principles will account for all: (1) Grandchildren like grandfathers (2) Tendency to small change «especially with physical change
(3) Great fertility in proportion to support of parents” [8
]. In other words, (1) heredity, (2) variation (Darwin thought variation was induced in large measure spontaneously in the reproductive process and by the environment—views he held throughout his writings), and (3) the Malthusian principle of overproduction.
Therefore, natural selection—though not called such until the next “book” in our series (the 1842 “Sketch”). Darwin had been using the expression “my theory” to mean “evolution.” But now, the expression “my theory” more specifically means “evolution by natural selection.” It is in 1839, toward the end of the series of “Transmutation Notebooks,” that Darwin takes his next logical, if not fateful, step: in page 118 of Notebook E, he exhorts himself to rederive his original patterns in terms of his ideas on how natural selection works to produce evolutionary change. He is by now far beyond his initial attraction to saltational evolution: rather natural selection must produce finely gradational change. This puts him at odds with his very first evolutionary pattern, as Darwin is aware that paleontologists see little evidence of such change in their collections of fossilized plants and animals. He writes (Notebook E, page 6): “My very theory requires each form to have lasted for its time: but we ought in same bed if very thick to find some change in upper & lower layers.—good objection to my theory
: a modern bed at present might be very thick & yet have same fossils” [8
] Darwin, an intellectually very honest man, was troubled by this “good objection” throughout his evolutionary writings—devoting a chapter to the problem and essentially inventing the science of taphonomy (study of the formation of the fossil record) in Origin of Species
After discovering natural selection in Notebooks D and E, Darwin turns renewed attention to both variation and the process of artificial selection in embryonic form— the analogy to what he would soon call “natural selection” by this time clear. The theme that varieties are incipient species—perhaps the most pervasive of Darwinian argumentative themes—is found in these notebooks [6
], as are some other, more rhetorical, devices that show up in the later works, including the Origin of Species
Particularly striking is Darwin's invocation of the travails of astronomers who labored so hard (occasionally relinquishing their lives!) to establish the laws of gravitation governing the behavior of celestial bodies. Darwin was not only fearful of attack on religious grounds, he also knew all too well that the only competing theory to explain the origin and diversity of life was in fact Judeo–Christian creationism. In Notebook B (page 101) [8
], Darwin writes: “Astronomers might formerly have said that God ordered each planet to move in its particular destiny—in same manner God orders each animal created with certain form in certain country, but how much more simple and sublime power let attraction act according to certain laws such are as inevitable consequence let animal be created, then by the fixed laws of generation, such will be their successors—let the powers of transportal be such & so will be the form of one country to another—let geological changes go at such a rate, so will be the numbers & distribution of the species!!” Later in the notebooks, he mentions persecution of the astronomers—and also writes (Notebook D, page 36): “What a magnificent view one can take of the world Astronomical <& unknown> causes, modified by unknown ones. cause changes in geography & changes of climate superadded to change of climate from physical causes.—these superinduce changes of form in the organic world, as adaptation. & these changing affect each other, & their bodies, by certain laws of harmony keep perfect in these themselves.—instincts alter, reason is formed, & the world peopled with Myriads of distinct forms from a period short of eternity to the present time, to the future—How far grander than idea from cramped imagination that God created (warring against those very laws he established in all organic nature) the Rhinoceros of Java & Sumatra, that since the time of the Silurian, he has made a long succession of vile Molluscous animals—How beneath the dignity of him, who is supposed to have said let there be light and there was light…” [8
This passage is “ancestral” to Darwin's most famous passage—concluding the Origin of Species
some 21 years later. Here we have not only the analogy with scientific law replacing creationist belief in astronomy, but also the origin of the famous phrase “there is grandeur in this view of life” [3
]. We even see here reference (albeit only in passing) to Javan and Sumatran rhinos—expanded and integral to the conclusions of each of Darwin's successive books on evolution.