None of these sugar-related expenditures of time and energy would exist if it werenât for the bargain that was struck about fifty million years ago between plants blindly âseekingâ a way of dispersing their pollinated seeds, and animals similarly seeking efficient sources of energy to fuel their own reproductive projects. There are other ways to get your seeds dispersed, such as windborne gliders and whirligigs, and each method has its associated costs and benefits. Heavy, fleshy fruits full of sugar are a high-investment strategy, but they can have a bonanza payoff: the animal not only carries away the seed, but deposits it on a suitable bit of ground wrapped in a large helping of fertilizer. The strategy almost never worksânot even once in a thousand triesâbut it only has to work once or twice in the lifetime of a plant for it to replace itself on the planet and keep its lineage going. This is a good example of Mother Natureâs stinginess in the final accounting combined with absurd profligacy in the methods. Not one sperm in a billion accomplishes its life missionâthank goodnessâbut each is designed and equipped as if everything depended on its success. (Sperm are like e-mail spam, so cheap to make and deliver that a vanishingly small return rate is sufficient to underwrite the project.)
Coevolution endorsed the bargain between plant and animal, sharpening our ancestorsâ capacity to discriminate sugar by its âsweetness.â That is, evolution provided animals with specific receptor molecules that respond to the concentration of high-energy sugars in anything they taste, and hard-wired these receptor molecules to the seeking machinery, to put it crudely. People generally say that we like some things because they are sweet, but this really puts it backward: it is more accurate to say that some things are sweet (to us) because we like them! (And we like them because our ancestors who were wired up to like them had more energy for reproduction than their less fortunately wired-up peers.) There is nothing âintrinsically sweetâ (whatever that would mean) about sugar molecules, but they are intrinsically valuable to energy-needing organisms, so evolution has arranged for organisms to have a built-in and powerful preference for anything that tickles their special-purpose high-energy detectors. That is why we are born with an instinctual liking for sweetsâand, in general, the sweeter the better.
Both partiesâplants and animalsâbenefited, and the system improved itself over the eons. What paid for all the design and manufacture (of the initial plant and animal equipment) was the differential reproduction of frugivorous and omnivorous animals and edible-fruit-bearing plants. Not all plants âchoseâ the edible-fruit-making bargain, but those that did had to make their fruits attractive in order to compete. It all made perfectly good sense, economically; it was a rational transaction, conducted at a slower-than-glacial pace over the eons, and of course no plant or animal had to understand any of this in order for the system to flourish. This is an example of what I call a free-floating rationale (Dennett, 1983, 1995b). Blind, directionless evolutionary processes âdiscoverâ designs that work. They work because they have various features, and these features can be described and evaluated in retrospect as if they were the intended brainchildren of intelligent designers who had worked out the rationale for the design in advance. This is not controversial in the general run of cases. The lens of an eye, for instance, is exquisitely well-designed to do its job, and the engineering rationale for the details is unmistakable, but no designer ever articulated it until the eye was reverse-engineered by scientists. The economic rationality of the quid pro quo bargains of coevolution is unmistakable, but until very recently, with the advent of human trade a few millennia ago, the rationales of such good deals were never represented in any minds.
Digression: This is a sticking point for those who donât yet appreciate just how well established the theory of evolution by natural selection is. According to a recent survey, only about a quarter of the population of the United States understands that evolution is about as well established as the fact that water is H2O. This embarrassing statistic requires some explanation, since other scientifically advanced nations donât show the same pattern. Could so many people be wrong? Well, there was a time not so long ago when only a small minority of Earthâs inhabitants believed that it was round and that it traveled around the sun, so we know that majorities can be flat wrong. But how, in the face of so much striking confirmation and massive scientific evidence, could so many Americans disbelieve in evolution? It is simple: they have been solemnly told that the theory of evolution is false (or at least unproven) by people they trust more than they trust scientists. Here is an interesting question: who is to blame for this widespread misinforming of the population? Suppose the ministers of your faith, who are wise and good people, assure you that evolution is a false and dangerous theory. If you are a layperson, you may be innocent in taking them at their authoritative word and then passing it on, authoritatively, to your children. We all trust the experts about many things, and these are your experts. But where, then, did your ministers get this misinformation? If they claim to have gotten it from scientists, they have been duped, since there are no reputable scientists who claim this. Not a one. There are plenty of frauds and charlatans, though. As you see, I will not mince words. What about the Scientific Creationists and Intelligent Design proponents who are so vocal and visible in well-publicized campaigns? They have all been carefully and patiently rebutted by conscientious scientists who have taken the trouble to penetrate their smoke screens of propaganda and expose both their shoddy arguments and their apparently deliberate misrepresentations and evasions.3 If you disagree heartily with this flat dismissal, you have two good choices to consider at this point:
Educate yourself in evolutionary theory and its critics and see for yourself whether what I say is true before proceeding. (The endnotes to this chapter provide all the references you will need to get going, and it should take only a few months of hard work.)
Suspend disbelief temporarily in order to learn what an evolutionist makes of religion as a natural phenomenon. (Perhaps your time and energy as a skeptic would be better spent trying to get to the heart of this evolutionistâs perspective in search of a fatal flaw.)
Alternatively, you may believe that you donât need to consider the scientific evidence at all, since âthe Bible saysâ that evolution is false, and thatâs all there is to it. This is a more extreme position than is sometimes recognized. Even if you believe that the Bible is the last and perfect word on every topic, you must recognize that there are people in the world who do not share your interpretation of the Bible. For instance, many take the Bible to be the Word of God but donât read it to rule out evolution, so it is just a plain everyday fact that the Bible does not speak clearly and unmistakably to all. Since that is so, the Bible is not a plausible candidate as common ground to be shared without further discussion in a reasonable conversation. If you insist it is, you are thumbing your nose at the whole inquiry. (Good-bye, and I hope to see you back again someday.)