Picking up where we left off last week (see my post of 05/20/13), in Chapter 2 of his Better than Human, Allen Buchanan identifies and discusses several major “limitations” of what he terms “unintentional genetic modification” (UGM), or “evolution as usual.” As I noted last time, Buchanan’s aim here is to adduce reasons for us to accept the idea that, in at least some instances, it may be preferable to pursue “intentional genetic modification” (IGM) rather than leaving the development of the human species up to UGM alone. To that end, he draws our attention to three major limitations of UGM.
First, UGM is “insensitive” to post-reproductive quality of life (pp. 32-34). That is to say, given that UGM acts only on (or with respect to) traits that are conducive to reproductive fitness, it also leaves intact a number of traits that greatly reduce quality of life after one’s reproductive years. More precisely, on the “Darwinian worldview” in terms of which Buchanan advances his argument, natural selection acts as a “gene filter”—that is, “it tends to prevent genes that have a greater negative impact on reproductive fitness than other genes from being passed on to the next generation” (p. 32, italics in original). As such, natural selection doesn’t operate beyond an organism’s reproductive years—which, for long-lived organisms such as human beings, can leave them with a whole host of problematic traits, ranging from decreased libido to increased risk of various cancers and cardiovascular disease, osteoarthritis, cognitive impairments such as dementia and Alzheimer’s disease, and the many other forms of degeneration that tend to accompany older age. This fact constitutes, according to Buchanan, “a sharp blow against the master engineer analogy.” After all, he asks, “[w]hat kind of master engineer creates beings that fall apart once they’ve reached post-reproductive age and makes no provision for repair?” By contrast, Buchanan suggests, “[o]ne of the chief advantages of IGM (intentional genetic modification) is that it could help us avoid or ameliorate the harms we suffer as a result of UGM’s insensitivity to post-reproductive quality of life” (p. 33). In fact, he goes on to suggest, given the significantly increased lifespans that the various “historical nonbiomedical enhancements” have made possible for us, “[w]e may need further enhancements—including biomedical ones—to cope with the consequences of these earlier enhancements” (p. 33). Indeed, “biomedical enhancements that enable us to live a very long life, with the worst ailments compressed into a very short period at the end, might be needed just to sustain the average level of well-being in our lives. In other words, paradoxically, we may need to enhance just to keep things from getting worse” (p. 34, italics in original)
There are additional problems with UGM. For one thing, as we have seen, natural selection leaves in place a whole range of negative traits, what Buchanan terms “Pleistocene hangovers”: traits that were presumably an “adaptation” at one point in time in the past but are not necessarily so now—and, indeed, that we would now consider to be “negative” traits that we would rather do without. Possible examples of such “hangovers,” Buchanan says, include such things as (a) our “predilection for sweet, salty, and fatty foods,” (b) the tendency of stepfathers to abuse their stepchildren, (c) xenophobia, and, perhaps, (d) the condition we now term Attention Deficit Disorder (pp. 35-36).
The important point that these and other such cases illustrate, Buchanan says, is that identifying a trait as an “adaptation” is a statement about the past—at some point in the past, trait X conferred a reproductive advantage—but says nothing about the present: “Yesterday’s advantage may be today’s liability, so the fact that a trait is an adaptation doesn’t mean it’s a good thing” (p. 35). Consequently, “[b]ecause the environment we live in now is so different, some of the traits we have that are adaptations… may be maladaptive today” (p. 35). But won’t natural selection eventually weed out such problematic traits? Not necessarily. It would, Buchanan says, be a “mistake” to make this assumption, for such traits
can cause serious problems for those of us who have them without reducing our reproductive fitness disastrously enough to get winnowed out. In other words, the mesh of the filter may not be fine enough to stop the genes responsible for them from being passed on and on. And even when they do have a negative impact on reproductive fitness, the evolutionary cure may be excruciatingly slow—taking many thousands of years (p. 36).
Here again, Buchanan suggests, IGM may offer a solution to the problem of Pleistocene hangovers: “In principle, IGM could clean up the ‘unwanted residue’ much more quickly and effectively. Less radically, drugs could be used to counteract the effects of Pleistocene hangover genes. Perhaps that’s what Ritalin does” (pp. 36-37).
UGM is not only a problem with respect to negative traits; it is also problematic when it comes to traits we consider to be positive. As Buchanan explains it, beneficial mutations spread only by way of a “nasty, brutish, and long” process (pp. 37-41). This is due to a number of features that are built into the process of natural selection. First, natural selection can only operate by way of “vertical gene transfer,” as opposed to “lateral gene transfer.” The former type of gene transfer occurs when a trait is passed down from one generation to the next, via sexual reproduction; the latter occurs when a gene is “incorporated” by an organism without having inherited that gene—as, for example, when a bacterium “grabs” a “beneficial” gene that happens to be “in the neighborhood” (p. 40). Generally speaking, organisms are only able to work (so to speak) with the genes they inherited from their parents—in other words, UGM is (with rare exceptions) limited to vertical gene transfer. As a result, the process of unintentional genetic modification, even when ultimately beneficial, tends to be “nasty, brutish, and long.”
By contrast, IGM opens up the possibility of introducing new genetic material for an organism to work with—a form of lateral gene transfer—and thereby, in turn, speeding up the process of genetic modification. Thus, instead of waiting for the “tightly shackled” workman—UGM—to do his work (a project that might take thousands of years and might never be completed), “[w]ith IGM, the workman can throw off his shackles and pick and choose what he needs” (p. 41).
A further problem with UGM is that “valuable” genes can be lost permanently, either through species extinction or through the reduction of genetic diversity that the process of natural selection inevitably brings about (recall the earlier point about natural selection acting as a “gene filter”). And that, Buchanan says, is “an unfortunate fact about UGM, because some genes that are irrevocably lost may be of great value for improving human life or even for preserving it in the face of new threats, whether natural or man-made” (p. 42). Here again, Buchanan sees IGM as potentially coming to the rescue: noting the establishment of seed banks and other similar “preservation” techniques, Buchanan suggests that “IGM, when combined with prudent preservation, can avoid the irrevocable loss of valuable genes” (p. 42).
Yet another built-in limitation of the process of UGM is what has been termed “local optimality traps”—the difficulty that because natural selection can operate only incrementally, it may not be possible to get from one state of development (reproductive fitness) to another, “higher” state of development (reproductive fitness) given the incremental steps that would be required to get “from here to there” in order to achieve that higher degree of “optimality.” The concept is technically complicated, but can be understood (as Buchanan relates it) in terms of an analogy to a three-dimensional “fitness landscape” (pp. 44-45), where relative height represents relative reproductive fitness. Suppose a species (say, human beings) has arrived at a certain “peak” of optimality—picture this as a mountain peak—such that it has greater reproductive fitness than other species that have not reached as high an elevation in the “fitness landscape.” From the vantage point of that “peak,” it may be possible to see in the distance a higher peak, some state of development that would represent a greater degree of reproductive fitness. The problem now is that, in order to reach that higher peak, the species in question would have to traverse a deep “valley,” representing a diminishment in reproductive fitness, in order to be able to ascend that higher peak. In such a case, that species would be stuck in a “local optimality trap.” The upshot, if we think of our own species as being in such a situation with respect to a given trait, is that “[w]e can’t increase our reproductive fitness, not because there are no biologically possible changes that would improve it, but because we can’t get there from here. Because natural selection is incremental, it can’t reach over the valleys to reach the higher peaks” (p. 45). This, Buchanan tells us, illustrates yet another way in which the “tinkerer is “tightly shackled”: “Because he works only incrementally, some improvements that are of enormous potential value are forever beyond his reach” (p. 45). IGM, on the other hand, might (at least in principle) be able to overcome this difficulty, by introducing “nonincremental” genetic change at the embryonic stage of human development (p. 45).
Finally, there is what Buchanan views as UGM’s “biggest limitation”—namely, the fact that “UGM selects for reproductive fitness, not human good” (pp. 45-48). Ultimately,
[f]rom the standpoint of evolution, to say that a trait is optimal means that no further incremental changes in the organism’s genes can improve the trait’s contribution to reproductive fitness. Optimal doesn’t mean unimprovable. It only means ‘the best that can be done, from the standpoint of reproductive fitness, given that this is where we are now and that we have to proceed incrementally’” (pp. 43-44).
In other words, “optimal” does not equal “best”—it simply means “most conducive to reproductive fitness” (p. 45). And, as we saw above, to say that X now has trait Y is not (necessarily) to say that Y is currently conducive to an organism’s reproductive fitness; it is, rather, to say that Y was conducive, at some point in the past, to the reproductive fitness of the species of which that organism is an instance. Furthermore, natural selection as such is indifferent to what we as a species value—that is, to the human good. It is, instead, merely concerned with the reproductive fitness of a given species, not with ensuring, for example, that human beings survive with a certain standard of quality of life. In other words, as Buchanan puts it, “reproductive fitness is about quantity, not quality” (p. 46). Given the foregoing, then, there are two erroneous inferences that must be resisted: (1) the inference from “X now has trait Y” to “Y must therefore now be contributing to X’s reproductive fitness,” and—importantly—(2) the inference from “conducive to X’s reproductive fitness” to being “good for X” (p. 46).
With this distinction between “reproductive fitness” and “human good” in place, Buchanan says, we can—and should—go on to ask ourselves the following crucial question: “In what sense, if any, is the existing version of humanity optimal?” (pp. 46-47). To which query he offers the following reply: “[i]f we answer this question on the basis of an accurate understanding of evolution, here’s what we can’t say. We can’t say that current human beings are the best, if this means best in terms of what we rightly value” (p. 47). In fact, “we can’t even say that we are best in terms of reproductive fitness; in fact, all we can say is that we’re doing well enough that the human population is increasing, not decreasing” (p. 47). Consequently, he concludes, “we have to steadfastly resist the common tendency to think that the latest product of the evolutionary process is the best, either biologically speaking, or in terms of human values. We can’t say we are the best in either sense, and that’s why we should take the prospect of biomedical enhancement seriously” (pp. 47-48).
Needless to say, there are numerous points to be made by way of critical engagement with the foregoing material. In the interest of keeping this post to a reasonable length, I will briefly mention just one of them here, and then follow up in this series’ next entry with a more detailed elaboration on this and related points of analysis.
Continuing a theme to which I have drawn attention in previous posts, I want to close this post with the observation that Buchanan’s reliance on the “limitations” of UGM as providing reasons for why we should consider it preferable, in at least some instances, to pursue IGM rather than leaving the development of the human species up to UGM alone runs into a serious epistemic difficulty. Specifically, the epistemic problem is this: given that, for Buchanan, evolutionary theory and the resultant “products of evolution” constitute the only permissible sources to which we can turn for information about human nature, how could we ever be in a position to know that we were actually improving or enhancing the human species by way of intentional genetic modification? If we are as epistemically limited as Buchanan says we are, then it’s hard to see how we could ever know either (a) what would be good for us (in the long run, at least) to aim for, or (b) whether, in the long run, IGM is likely to be either (i) more effective or (ii) more beneficial to us. For all we know, UGM and IGM might be equally effective and/or beneficial, or UGM might turn out to be more effective and/or beneficial in the long run, present appearances aside. In the end, we just don’t know—and that, in turn, may very well favor a strong presumption in favor of caution over against enthusiasm regarding the enhancement enterprise
Works Cited in this Post:
Buchanan, A. (2011). Better than Human: The Promise and Perils of Enhancing Ourselves (Philosophy in Action Series). New York: Oxford University Press.
 As the reader will recall, Buchanan defines these two terms as follows: “UGM is evolution as usual, what Darwin called ‘descent with modification,’ where a driving force of the modification is natural selection. UGM, in other words, is evolution without intentional modification of human genes by human beings. IGM is intentional modification” (p. 31).
 For the sake of clarity here, it should be recalled that when Buchanan refers to the “master engineer,” he is referencing what he terms the “master engineer analogy,” where “natural selection” assumes the place, in the post-Darwinian era, that “God” held previously in “Intelligent Design” or “pre-Darwinian religious” views of nature. (p. 28).
 See my post on 03/25/13 for more on the “historical nonbiomedical enhancements.”
 Referring to the “Pleistocene era” (approximately 100,000-150,000 years ago), the period to which evolutionary biologists trace the emergence of most of our current biological traits (p. 35).
 To the objection that this might run the risk of creating a “monoculture,” Buchanan responds by observing, first, that UGM itself reduces genetic diversity, and that, second, the use of IGM may turn out to be our only way of countering such loss of diversity. In the end, he concludes, “if we value genetic diversity, we should worry more about UGM and less about IGM” (p. 43).