For Timothy Shanahan, a single sentence from The Origin of Species raises all of the most important philosophical questions about the Darwinian theory:

The questions fall into three categories: selection, adaptation, and progress. Each is treated in a separate section that begins with an analysis of Darwin's original meaning, ends with current debates among philosophers and biologists, and includes a selection of historical developments in between. Shanahan presents all sides of the discussion with admirable clarity and evenhandedness, which will make the book useful for teaching graduate students and advanced undergraduates.

Although its title might seem to announce a historical work, The Evolution of Darwinism is better described as a philosophical survey that uses historical material to shed light on questions of present-day interest. Shanahan recognizes that scientific theories and philosophical debates change over time, and that interpretations of Darwin change with them, because “[s]howing that one's own view is the same as Darwin's can serve as a powerful rhetorical device in legitimating one's view” (7). He does a good job of exposing how others have appropriated Darwin to make their own points, and, subtly, he also puts Darwin to work for his own purposes.

The Selection chapters deal exclusively with the levels-of-selection problem. Shanahan makes fast work of Michael Ruse's reading of Darwin as an individual selectionist and turns Darwin into more of a pluralist, who generally favors individual-level interpretations, but switches readily to families or tribes whenever he needs them to craft a superior explanation. From Darwin, the story skips to the vehement rejection of group selection in the 1960s, and thence to the more recent diversification of views about structured demes, altruism, and selfish genes, the genic pluralism of Sterelny and Kitcher, and the holism of developmental systems theory. Shanahan himself turns out to be a kind of pluralist, like Darwin. He grants the genic view the greater generality, simplicity, and predictive power, but for a realistic account of biological causality, he finds that multiple levels must be dealt with in all their complexity.

The section on Adaptation shows the mature Darwin backing down from previous assertions about the power of natural selection to perfect the organism. In late editions of The Origin, Darwin acknowledges the limitations and constraints on selection and becomes something like a methodological adaptationist, i.e., one who proceeds as if all characteristics may be expected to be products of selection and adaptation, but who is willing to fall back on other explanations should the selection hypothesis not be supportable. In the twentieth century, the Modern Evolutionary Synthesis picks up where Darwin left off, giving nonselective factors like genetic drift their due, but it develops in the opposite direction from Darwin and ‘hardens’ in its reliance on selection and adaptation. The 1979 critique by Gould and Lewontin then renders this kind of selectionism-adaptationism problematic, but fails to bring the field all the way back to the Darwin of the sixth edition. The rest of the section concerns current discussions about how to define ‘adaptation’, how to tell when a characteristic should qualify as one, and what forms of adaptationism are still legitimate in the wake of Gould and Lewontin. Methodological adaptationism emerges as the safest and most productive option. It can expose the limits of its own assumptions and bring to light the rich diversity of evolutionary processes other than selection.

The last section is about the tendency to “progress towards perfection.” Here Shanahan gives his strongest and most sustained historical analysis (some if it relegated to an appendix). He brings out Darwin's dual yardsticks for measuring progress—competitive superiority and specialization or division of labor—and he makes it clear that Darwin expected the general result of natural selection to be progressive, but also recognized that progress could not be a law of nature. Shanahan defends the middle ground against authors who make Darwin either overly progressive or overly nonprogressive. Gould's nonprogressive Darwin is subjected to the most detailed critique. Skipping ahead to the Evolutionary Synthesis, Shanahan shows progressivism still flourishing, particularly in the work of Julian Huxley and G. G. Simpson, and for once, he compares the synthetic theory favorably to Darwin's own Darwinism. In the discussion and conceptual analysis that follow, he endorses a carefully circumscribed notion of progress.

Only the last chapter of the section on Progress addresses human evolution, which is unfortunate, for as Shanahan tells us at the outset, Darwinism stands out among the great scientific achievements precisely because of its implications for human self-understanding. In this chapter, Darwin's Descent, Wallace's spiritualism, eugenics, Nazi racial ideology, sociobiology, Darwinian medicine, evolutionary psychology, and the inevitability of human evolution and its possible future, all go by very quickly and are kept segregated from the ‘evolution of Darwinism proper'. Shanahan thus misses an opportunity to show how competing human self-conceptions might have informed rival interpretations of Darwinism, motivated their development, and made the field both contentious and historically important. When the big questions about selection, adaptation, and progress are stripped down to such bare conceptual bone, it becomes hard to imagine what there ever was to fight over tooth and nail.