As I noted in Part 1 of this series (see my 03/25/13 post), in Better than Human Allen Buchanan considers four major lines of objection to the “enhancement enterprise.” As Buchanan summarizes them, each of these objections claims that biomedical enhancement is “different” in morally significant ways from other kinds of (nonbiomedical) enhancement. Specifically, these objections assert that:
(1) biomedical enhancements are different because they change our biology; (2) biomedical enhancements are different because (some of them) change the human gene pool; (3) biomedical enhancements are different because they could change or destroy human nature; [and] (4) biomedical enhancements are different because they amount to playing God (p. 12).
In Chapter 2, Buchanan takes on the second and third of these objections—that is, the “changing the human gene pool” and “changing human nature” objections, respectively.
The heart of Buchanan’s discussion in this chapter is a consideration of two competing analogies in terms of which one might understand evolutionary biology—or, alternatively, “nature” (p. 29)—and its processes: the “master engineer” and the “grim tinkerer” analogies, respectively. On the former analogy, “organisms are like engineering masterpieces: beautifully designed, harmonious, finished products that are stable and durable (if we leave them alone)” (p. 29). On the latter, evolution is “morally blind,” “fickle,” and “tightly shackled” (p. 49)—it produces “cobbled-together, unstable works in progress, and then discards them” (p. 28).
Evolution is disanalogous to a master engineer, Buchanan says, in two key respects. First, “natural selection never gets the job done” (p. 28). Environments are constantly changing, and organisms are constantly adapting both to their environments and to each other, in “a ceaseless round of adaptation and counteradaptation” (p. 28)—resulting in further changes both to organisms and their environment, in a process that never arrives at a terminus. So rather than being “the end points of a process whereby they climb a ladder to perfect adaptation to their environment,” organisms instead exist in a state of perpetual instability, one that belies the “finely balanced” nature implied by the master engineer analogy (pp. 28-29). Second,
unlike a master engineer, evolution doesn’t design what it produces according to a plan that it draws up in advance. Instead, it modifies organisms in response to short-term problems, with no thought of long-term effects. Evolution has no overall game plan for any species, and the results show it. What’s useful for solving today’s problems can cause new problems—and even extinction—down the line (p. 29).
In the final analysis, Buchanan contends, “evolution is more like a morally blind, fickle, tightly shackled tinkerer” than a master engineer. The burden of the rest of the chapter is to provide reasons why (on Buchanan’s view) we ought to accept this analogy over against the master engineer analogy.
In order to adjudicate between these two analogies, Buchanan says, we need to grasp certain key aspects of the mechanisms of evolution (p. 29). The first thing to notice in this regard is that nature is replete with instances of “suboptimal design” (pp. 30-31), which Buchanan takes to be prima facie evidence that the master engineer analogy is problematic at best. Examples of such “design flaws” include, inter alia, the fact that in male mammals the urinary tract “passes through (rather than being routed around) the prostate gland, which can swell and block urinary function,” and the “hasty shift from quadruped to biped, which resulted in back and knee problems and a birth canal that passes through the pelvis, resulting in greatly increased risks to both mother and child in the birthing process” (p. 30). Numerous additional examples could be cited (and Buchanan cites several other illustrative examples here). “Design flaws” such as these led Darwin to develop his theory of natural selection, with which, Buchanan informs us, “Darwin debunked the argument from intelligent design, one of the traditional arguments for the existence of God, by cataloguing the ‘clumsy, blundering, wasteful’ works of nature” (p. 30).
To show more clearly why nature is not best thought of as a “master engineer,” Buchanan introduces at this point a distinction between what he terms “Unintentional Genetic Modification” (UGM) and “Intentional Genetic Modification” (IGM). UGM is “evolution as usual, what Darwin called ‘descent with modification,’ where a driving force of the modification is natural selection”—in other words, “evolution without intentional modification of human genes by human beings” (p. 31). IGM, then, in the context relevant to our discussion, is intentional modification of human genes by human beings.
Buchanan’s aim here is actually two-fold: first, he wants to provide reasons why we ought to reject the “master engineer” analogy in favor of the “grim tinkerer” analogy, and second, he wants to give us reasons for considering the possibility that it may be preferable, in at least some circumstances, to actively pursue IGM rather than simply leaving the development of the human species entirely to UGM. His subsequent discussion in the remainder of this chapter is designed to accomplish both of these aims simultaneously. To that end, he begins by enumerating some of the built-in limitations of UGM, and then goes on to describe some ways in which IGM might be employed to overcome those limitations.
In the next post in this series, we’ll finish up our explication of Buchanan’s argument, and then develop some critical observations regarding that argument. By way of preview, three major limitations of UGM to which Buchanan draws our attention are the facts that (1) UGM is “insensitive” to post-reproductive quality of life (pp. 32-37); (2) in UGM, beneficial mutations spread only by way of a “nasty, brutish, and long” process (37-45); and (3) UGM selects only for “reproductive fitness, not human good” (pp. 45-48). Critical remarks will focus, in turn, on several epistemological, ontological, and moral issues raised by the way Buchanan frames and develops his argument in this chapter.
 A bonus for the philosophy buffs out there: In the context of this discussion of “design flaws,” Buchanan offers an arresting image in answer to Nagel’s famous query regarding what it’s like to be a bat. As Buchanan explains, “bats spend a good deal of their time hanging upside down, closely packed together, with their feces pouring down over their bodies to their heads. (Imagine yourself holding a toothpaste tube upright and squeezing it until the contents cover your hands. That’s what it’s like to be a bat.)” (p. 31).