The Sperm of Sea Urchins and the Directedness of Natural Processes


Nature exhibits finality and purpose in its various activities, and chance is not, indeed cannot be, an explanation for this activity.

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The March press release from the Max Planck Institute in Germany was certainly provocative: "Sperm can do calculus!" Not least because the sperm in question is that of the sea urchin—engaging in activity which, for human beings, must await advanced courses in high school or university. Researchers at the Center of Advanced European Studies and Research in Bonn are convinced that by "chemotactic signaling," related to subtle changes in an internal calcium environment, the sperm of sea urchins adjust their movement with "only one aim: to find the [female] egg."

To speak of "aims" or "goals" of natural processes calls to mind the oft-repeated claim that modern science no longer concerns itself with purpose, that teleology is an outmoded notion. How often do we hear that biology, especially evolutionary biology, discloses a world of living things which is, at its core, unguided, unplanned, and the result of random processes? Such an attribution of randomness, chance, and ultimate meaninglessness to the conclusions of biology often leads believers (and non-believers) to think that there is a stark choice between evolutionary biology and any traditional notion of divine providence, a providence disclosed in the ordered regularities in nature.

After all, Richard Dawkins has written that the universe described by biology "has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind, pitiless indifference." Or think of the philosopher, Daniel Dennett, who observed: "Love it or hate it, phenomena like this [DNA] exhibit the heart of the power of the Darwinian idea. An impersonal, unreflective, robotic, mindless little scrap of molecular machinery is the ultimate basis of all agency, and hence meaning, and hence consciousness, in the universe." Although many biologists would reject the rhetoric, if not the philosophical judgment, embodied in claims by Dawkins, Dennett, and others, there remains a deep-seated suspicion of any appeal to teleology—that is to explanations in terms of purpose—based on the evidence of contemporary biology.

To see how the behavior of the sperm of sea urchins is relevant to wider discussions about purpose or directedness in natural processes, we ought to look a little more to the empirical evidence concerning their movement. The scientists speak of chemotaxis, movement in the direction of a chemical substance: the sperm follows the trail of an attracting agent emitted by the egg cell. Calcium ions in the sperm's tail direct the swimming patterns of each sperm. The behavior is correlated to changes in the calcium concentration in the sperm. What astonished the researchers, according to the press release, was that "the sperm tail [the navigator, as it were] only reacted to the time derivative of the calcium concentration. . . To put it simply: sperm can perform calculus! Exactly how they do it is unclear."

Despite accounts of the chemistry involved in the movements of the sperm, the mystery remains. As one author for the Max Planck Institute observed: "After all, these sperm are not intelligent creatures: they have no real nose, not to mention nerve cells that could transmit sensory stimuli to the brain, which, of course, they lack in the first place." What is important here, I think, is not the detail of the chemical processes, but the realization provided by scientific evidence of end-directed, intelligible behavior in nature. The chemical processes, which are intrinsic to the sperm, have an order, regularity, and goal-directedness, despite the fact that the agency involved is surely not that of an intelligent creature. Accounts of research concerning the sperm of sea urchins can serve as an occasion for reflection on how properly to speak of purpose in nature, a topic highly contested in discussions about the implications of biology for traditional notions of order, design, and divine providence.

What may appear to many to be strange claims about sea urchins help us to see that the natural sciences cannot really escape references to directedness. The laws and conditions which the sciences describe are more than simply patterns of regularities that we observe; that patterns must have some sufficient cause in nature itself. At least this must be true if we think that science offers us knowledge of nature: that science is about the world and not just an analysis of concepts we use to describe the world. The "calculations" attributed to the sperm of sea urchins is a way of offering a kind of mathematical description of the regularities evident in their behavior. To speak of regularities in nature, or of there being laws of nature, means that there are processes oriented towards certain general ends, and that these processes are rooted in the very structure of nature itself.

As the scientist William Stoeger observes, if there were no end-directed or end-seeking behavior in physical reality, there would be no regularities, functions, or structures about which we could formulate laws of nature, and, thus, there would be no science of nature. There is in these natural entities an intrinsic capacity for motion and for self-organization. Rather than speaking of nature's obeying laws, which brings with it perhaps a sense of voluntary agency (e.g., the act of obeying), it would be better to note that there are intrinsic principles or sources of behavior which manifest themselves in those regular patterns which can be described and modeled, often in mathematical terms.

It is surely true that there are chance events in nature; not all processes reach the ends toward which they tend. Biologists also speak of genetic mutations as chance events. But, as the distinguished biologist Francisco Ayala reminds us, such mutations are not without causes; they are only "chance" in the sense that they are not necessarily directed to the good of the organism in which they occur. The reality of chance events among living things, and whatever indeterminacy and unpredictability result, do not justify making chance an ultimate explanatory principle. Chance events occur within nature: within the context of a reality susceptible to rational investigation because it is intelligible, and it is this intelligibility which makes possible the laws of nature. Indeed, chance is really meaningless apart from a recognition of finality. It is only because we do notice that things regularly act to achieve ends that we recognize the failure of this to happen, that is, chance.

There is a useful distinction, employed by Ayala, between "external teleology," the result of the purposeful action of an agent (e.g., when human beings make things) and "internal teleology," when teleological features are the result of exclusively natural processes. The example Ayala uses, for the latter, are the wings of birds. They have a natural teleology; they serve the purpose of flying, but they are not the result of the design of a conscious agent. Here we must remember that the conscious agent whom Ayala excludes as the source of natural teleology is an external agent acting in the world: an agent not fundamentally different from other agents, even if more powerful.

Ayala distinguishes between two kinds of internal or natural teleology: 1) bounded or determinate or necessary teleology; and 2) unbounded or indeterminate or contingent teleology. An example of the first is the achievement of a specific end state in spite of environmental fluctuations. Embryological developments, from fertilized egg to adult, are examples of such bounded natural teleology. The characteristics of the mature adult are essentially determined in the fertilized egg. On the other hand, contingent or unbounded natural teleology "occurs when the end state is not specifically predetermined but rather is the result of selection of one from among several available alternatives." Ayala's claim is that when we speak of the adaptations of organisms being "designed," it is in the contingent teleological sense. The wings of birds, designed as they are for flying, did not have their source in some remote ancestor such that their appearance was necessitated or determined.

The origin of real design and intelligible order in biological phenomena can be explained without having recourse to a conscious agent directly operating in nature to produce this design. Such a view would only exclude God as the ultimate explanation for design in nature if one were mistakenly to think that God is an agent in nature differing only in degree from other conscious agents. We must remember, however, that God transcends the created order in which He acts in such a way that He "differs differently" from all other causes. God is really not an "external agent," nor is divine agency incompatible with chance events.

It is important to remember that to say that nature discloses intelligence—in part because of the order, design, and teleology in nature—need not mean that there is an intelligent agent in nature as one of the causes which the empirical sciences need to take into account. The recognition of teleology in nature is not first of all the discovery of intelligent agency. Nevertheless, the natural philosopher, using many of the distinctions Ayala draws about teleology, can argue from the intrinsic finality in nature to its ultimate source without making the mistake of conceiving of this source as simply an external agent.

Finality and purpose in nature, whether bounded or unbounded, to use Ayala's categories, call for an explanation. Chance is not, indeed cannot be, such an explanation. The mystery of the behavior of the sperm of sea urchins remains, even after the elaborate description of that behavior in terms of chemical activity. Researchers studying sea urchins and their reproductive processes point to the complex and intelligible activity—a kind of chemotaxis—which they have discovered. This discovery invites further reflection about the intrinsic source of such behavior, and chance cannot be an explanation, even if the goal of this behavior is in many cases not realized.

For natural philosophers in the tradition of Thomas Aquinas, an understanding of what nature is can help to resolve, or at least clarify, what scientists at the Max Planck Institute refer to as the "mystery" of the behavior of the sperm of sea urchins—and by extension of the regular behavior of all natural entities. Modern biology discloses a dynamic world of change: a dynamism which has its source in intrinsic principles found in nature. There are real self-organizing principles in living things.

The agency evident in natural processes ought not to be seen immediately as the result of some conscious agent. There is a broad sense of "agency" in nature which includes hearts' pumping blood, animals' acting instinctively, plants' engaging in photosynthesis, genes' mutating, and the like. Thomas uses an apt analogy to make this point, and to locate its ultimate source in God's creative act: "Nature is nothing but a kind of art, that is, the divine art, impressed upon things, by which these things are moved to a determinate end. It is as though the shipbuilder were able to give to timbers that by which they would move themselves to take the form of a ship." The real causality evident in nature does not compete with or replace divine agency. God's omnipotence is such that He causes nature to possess a dynamic, intrinsic source of its own activity.

The extraordinary details of the behavior of the sperm of sea urchins, in terms of "chemotactic signaling," and the ways in which this signaling can be expressed as a kind of calculus, show us that explanations in terms of ends or goals remain an important feature of biology. Despite a kind of teleophobia, a fear of referring to aims or purposes in nature, exhibited by many commentators, the natural sciences really do describe a world suffused with goal-directed activity. As Thomas Aquinas would remind us: "it is contrary to the meaning [ratio] of nature to say that nature does not act for the sake of something." Just look to sea urchins.

William E. Carroll is the Thomas Aquinas Fellow in Theology and Science at Blackfriars Hall and a member of the Faculty of Theology of the University of Oxford.

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