The Panda’s Thumb by Stephen Jay Gould Read Free Book Online Page A

perform many other, unselected functions as well.
    Wallace stated the hard hyper-selectionist line—“pure Darwinism” in his terms—in an early article of 1867, calling it “a necessary deduction from the theory of natural selection.”
    None of the definite facts of organic selection, no special organ, no characteristic form or marking, no peculiarities of instinct or of habit, no relations between species or between groups of species, can exist but which must now be, or once have been, useful to the individuals or races which possess them.
    Indeed, he argued later, any apparent nonutility must only reflect our faulty knowledge—a remarkable argument since it renders the principle of utility impervious to disproof a priori: “The assertion of ‘inutility’ in the case of any organ…is not, and can never be, the statement of a fact, but merely an expression of our ignorance of its purpose or origin.”
    All the public and private arguments that Darwin pursued with Wallace centered upon their differing assessments of the power of natural selection. They first crossed swords on the issue of “sexual selection,” the subsidiary process that Darwin had proposed in order to explain the origin of features that appeared to be irrelevant or even harmful in the usual “struggle for existence” (expressed primarily in feeding and defense), but that could be interpreted as devices for increasing success in mating—elaborate antlers of deer, or tail feathers of the peacock, for example. Darwin proposed two kinds of sexual selection—competition among males for access to females, and choice exercised by females themselves. He attributed much of the racial differentiation among modern humans to sexual selection, based upon different criteria of beauty that arose among various peoples. (His book on human evolution —The Descent of Man (1871)—is really an amalgam of two works: a long treatise on sexual selection throughout the animal kingdom, and a shorter speculative account of human origins, relying heavily upon sexual selection.)
    The notion of sexual selection is not really contrary to natural selection, for it is just another route to the Darwinian imperative of differential reproductive success. But Wallace disliked sexual selection for three reasons: it compromised the generality of that peculiarly nineteenth-century view of natural selection as a battle for life itself, not merely for copulation; it placed altogether too much emphasis upon the “volition” of animals, particularly in the concept of female choice; and, most importantly, it permitted the development of numerous, important features that are irrelevant, if not actually harmful, to the operation of an organism as a well-designed machine. Thus, Wallace viewed sexual selection as a threat to his vision of animals as works of exquisite craftsmanship, wrought by the purely material force of natural selection. (Indeed, Darwin had developed the concept largely to explain why so many differences among human groups are irrelevant to survival based upon good design, but merely reflect the variety of capricious criteria for beauty that arose for no adaptive reason among various races. Wallace did accept sexual selection based upon male combat as close enough to the metaphor of battle that controlled his concept of natural selection. But he rejected the notion of female choice, and greatly distressed Darwin with his speculative attempts to attribute all features arising from it to the adaptive action of natural selection.)
    In 1870, as he prepared the Descent of Man , Darwin wrote to Wallace: “I grieve to differ from you, and it actually terrifies me and makes me constantly distrust myself. I fear we shall never quite understand each other.” He struggled to understand Wallace’s reluctance and even to accept his friend’s faith in unalloyed natural selection; “You will be