Historically, biology educators have been chiefly concerned with the role of teleology in evolution education (for example, Bartov 1978, 1982 as an early benchmark and, more recently, Galli and Meinardi 2011; Werth 2012, 2014; and others in this volume). Concerns highlight (at least) misleading images of progress, of inevitability, of directed (Lamarckian) variation, of “intelligent” design (as if mediated by a Creator), of functional optimality, and of privileged taxa or lineages. That is, there is inadequate appreciation of historical contingency (or “chance” or “accident”), natural selection as stepwise and local, changing environments, evolutionary “reversals,” vestigial structures, pleiotropy, genetic drift, evolutionary branching, and the role of teleonomic explanations. All are indeed important. However, our focus here is much broader. We show how teleological thinking—or at least teleological language and metaphors—permeate student thinking other areas of biology, as well.

Consider, first, Humboldt’s case of taxonomy. Linnaeus, of course, imposed a welcome order on what was earlier a vast and unwieldy catalog of living creatures. But while his “method provided desperately needed standards… its criteria for classification were somewhat arbitrary” (Helferich 2004). Linnaeus judged organisms largely by appearance, failing to recognize that external similarity is often a poor guide to structural or developmental relatedness. He also believed in the immutable fixity of species as expressions of an eternal plan of creation. For example, mammals were named mammals in part to profile mammary glands as essential by design, including related “natural” maternal responsibilities (Schiebinger 1993a, b). With the advent of Darwinian evolution, our view of the diversity of life shifted substantially. We now think phylogenetically, in terms of homology and derived features. We think in terms of common ancestors and branching, not of hierarchical levels of similarity. And yet the underlying philosophy of organization that Humboldt so vigorously critiqued remains largely intact. Seven levels stretch from kingdom to species, each registering a presumptive degree of similarity. Today’s Linnaean taxonomic system is a vestige, in a sense, of eighteenth-century teleology.

Another powerful teleological concept in biology has been the “balance of nature.” Professional ecologists today have certainly rejected the notion. But historically, many biologists embraced it (Egerton 1973; Kricher 2009). For example, Rachel Carson used it effectively as a central and persuasive theme in Silent Spring (Allchin 2014). Students nowadays espouse notions of balance, once considered good biology (for a summary of research, see Allchin 2014). Namely, populations supposedly self-regulate their size so as not to exhaust food resources. (Even the concept of carrying capacity implies that one can imagine a population in a stable—or “sustainable”—equilibrium.) “Balance of nature” is also taken to mean that species coordinate interactions, contributing to a harmonious coexistence. For instance, predators “need” to keep prey populations in check (often, for their mutual benefit). Accordingly, a reduction of the wolf population in Yellowstone was described by a journalist in 2009 as leading not just to more elk, but to an “overabundance” of elk. Likewise, fungi and reducers are “needed” to recycle nutrients in an ecosystem. Also, stability is the norm. So one does not expect untoward disturbance (floods, hurricanes, volcanoes)—or else things quickly return to their “normal” (“balanced”) state. In almost all cases, “balance” is a normative concept of how nature should be (Zimmerman and Cuddington 2007): nature is balanced (teleologically) because it is supposed to be balanced. Hence, one might hear that forest fires are “needed” to rejuvenate communities or to pave the way for ecological succession. Such appeals to the balance of nature, while scientifically discredited, still permeate the rhetoric of environmentalism, where it appears under the guise of scientific respectability. While ecologists formally eschew the concept of balance of nature, it remains a widely adopted preconception and a feature of language that seems not to disappear entirely.

Students also exhibit a similar normative misconception that the body should exhibit an inherent “balance” or intended “normal” state, and that this is governed by immanent “wants” or “needs,” quite apart from any meaningful understanding of homeostatic mechanisms. Namely, the body achieves stability because, ultimately, it is supposed to be stable. For example, a hit 1960s love song celebrated the presumed standard body temperature (in °F): “Hey, 98.6, it’s good to have you back again.” Deviation seems wrong (in a normative sense) and thus leads to restoration of a “normal” or essentialist state. Someone who is ill will “get well soon,” regardless of and independent of any immunological system. Thus, for centuries, scientists misled themselves into viewing fevers as “unnatural” and symptomatic of pathology. The unstated assumption of an “ideal” steady state as a “natural” norm eclipsed the concept of a dynamic equilibrium, where the body might instead have an adaptive response (to reset temperature, making an unwelcome environment for pathogens).

Likewise, medicine was long prejudiced by a presumed universal “normal” condition as a prescriptive norm. Medical ethicists have now recognized “normality” as a value judgment, not any objective state (see, for example, Boorse 1977; Caplan 1989; Englehardt 1974; Sacks 1985). So, too, for genetic development. Even among scientists, rare developmental conditions were long considered pathological “monsters” or “errors,” not instantiations of expected variation (for fuller discussion, see Allchin 2017, pp. 125–131). Genetic conditions such as muscular dystrophy, cystic fibrosis, sickle cell anemia, phenylketonuria, Down’s syndrome, and so forth, are still typically characterized as “diseases.” Yet that label presumes a narrow sense of what “should” develop: another normative expression of intentional purpose.Footnote 2 Physiology and development, like ecosystems, are commonly interpreted as meant to purposefully stay in “balance.”

Consider, next, teleology at the level of molecules: most prominently, in how biologists conceptualize and talk about DNA, especially to non-biologists (see Heine 2017; Moss 2003). That is, the standard characterizations of genetics lend a sense of intentional agency and even intelligent purpose to genes and the cell processes they indirectly help precipitate. Namely, DNA/genes provide information. Ostensibly, that indicates a cognizant, “informed” agent. DNA, one hears, provides the “blueprints” or “instructions” for life, implying an architect or designer who drafted the plans. Indeed, DNA has its own “language.” The language is of base pairs, typically designated with four letters (A, T, C, G): the image conveyed is thus of abstract symbols, not of physical three-dimensional shapes that constrain molecular interactions. Intention continues. The “message” of the DNA is “read” by an enzyme which “transcribes” the information, generating a “messenger” molecule, RNA. The reality of large macromolecules tumbling randomly through cellular protoplasm and occasionally encountering a complementary shape does not readily spring to mind. The “information” may then be “edited,” as though by a purposeful editor, and “carried,” as though by a purposeful courier, to the ribosome, which again “reads” the “message” and “translates,” as though by a purposeful cryptologist, its genetic “code.” The role of entropy and energy release as ineliminable causal factors are rarely mentioned. The whole causal cascade seems to depend on autonomous linguistic agents deliberately communicating to one another, not on thermodynamics.

Collectively, the terms we use to describe DNA are potent. They contribute to its image as a purposeful “master molecule.” Its agency extends (through a planner’s mindful “blueprints,” recall) to the development of a whole organism from just one cell. Genes seem to have extraordinary power. That might include one allele exerting “dominance” over another (a view that elicits many further misconceptions about evolution and population genetics; see Allchin 2005). At the extremes, we encounter talk of “selfish” genes and genocentric evolution. An organism is supposedly no more than a genome’s way of making another genome. No one should wonder why students (and the broader culture) develop a misleading view of genetic determinism (Heine 2017): it is embodied in the very language that biologists use, imparting agency, purpose, and, indeed, intent to a set of molecules whose shapes incidentally have particular causal relevance.

For biologists, of course, the notion of information may be formally “just” a metaphor. But in their analysis of the Metaphors We Live By, philosophers George Lakoff and Mark Johnson (1980) remind us that analogies and contingent associations carry with them substantive and constitutive meaning. It may well be impossible to communicate without metaphors, but this does not discount their import. In this case, the DNA-as-information metaphor embodies considerable teleology. When instructors educate beginning biology students with such loaded language—even if unwittingly and with the best of intentions—they promote a view of individual molecules either acting with deliberate agency or by their fulfillment of a plan inscribed in them by some other agent.

The teleological view of genetics helps further foster a teleological view of species essentialism: that each species’ distinctive traits are universal, determined by its own unique “purpose” (on the iconic case of tiger stripes and leopard spots, see Allchin 2019). Folkbiological essentialist conceptions of species exhibit idealism and include a distinctive normative dimension (Gelman and Rhodes 2012; Griffiths 2002). Like “just-so stories,” these essentialist conceptions describe a species that (in the holder’s mind) is “self-justified” and inevitable. But nowadays, identity is frequently traced to genes (for a fuller discussion, see Allchin 2017, pp. 141–144; Heine 2017). Thus, altering a species’ genetic make-up is viewed as tampering with its “natural” essence. Insert a few genes (or just one) in a crop plant and it suddenly becomes seen as a monstrous “Frankenfood.” Genetically modified organisms (GMOs) are thus widely condemned as “wrong” simply because they are “modified.” They are perceived as compromised or “unnatural,” violating an implicit norm of essentialist purpose (for fuller discussion, see Allchin 2017, pp. 192–197). By contrast, when similar genetic changes occur in humans, where they are labeled gene therapy, they are widely endorsed as a benefit. The term “therapy” is not suggestive of any essential change. It seems more like a welcome transplant via molecular surgery. The teleological views of species identity and genetics are closely allied.

The information metaphor is also found in physiology. Hormones are typically described as “messengers,” likening them to a telegram or courier that “delivers information” to a “receptor” cell surface protein that “interprets” it. It is not the hormone itself, nor its physical shape, that seems causally important, but again the abstract “information” it somehow contains or encodes. In addition, hormones are typically depicted as traveling from their source directly “to” (teleologically) their “target” cells. No bloodstream “pinball,” with repeated mismatches as the hormones collide randomly with cell surfaces until a matching receptor protein is encountered —quite the contrary to a sense of messages “delivered” straight to where they “ought to go”.

In a similar way, neurons and nerves are described as carrying information, too. The inevitable image is one of telephone wires or fiber optic cables running through the body. But such information-rich human communication channels are misleading models for the binary action of neurons: they either send an impulse (when causally triggered) or they remain in a ready state. The impulse itself has no further “information.” True, the impulses may vary in frequency, and nerve pathways may converge or diverge at synapses with significant effect. However, the basic “message,” if there is one, is hardly more than a percussive beat. The “pain signal” from a finger, or the “blue signal” from a retina, or the “stretch signal” from a carotid artery, are all fundamentally the same: a burst of neurotransmitters into the synaptic cleft as the result of an all-or-none action potential down the cell’s axon. The thing that differentiates them is which pathway has been stimulated—like when manor house servants hear an indefinite bell ring and, to discern which room has requested service, have to consult the lingering motion of one particular bell among many bells on the cellar wall (Fig. 1). The “meaning” of the nerve impulse is determined solely by the map of the network, not by the nature of the impulse. Neurons are not, any more than hormones, teleological agents.

Fig. 1 (photo by Alex Welsh, courtesy of the New York Times) Servant bells displayed at “Downton Abbey: The Exhibition” Full size image

Information and cognition is also implied in the concept of immune “memory.” Thus, one might hear that an antibody “recognizes” an earlier pathogen type, like someone recalling the face of a former intruder. But there is no conscious “recognition,” only a rapid positive feedback cycle triggered by the renewed presence of an antigen. Immune cells are also said to “recognize” self from non-self. They “communicate” with one another through a secure “double-handshake”—in the mode of a conscious acknowledgment upon greeting another cell that can provide the secret counter-password.

Other examples abound. Here, we briefly mention just a few more—a mixture of student misconceptions and unguarded classroom talk. For example, ions “need to” cross membranes to flow down concentration gradients. Ligands “need to” bind with their target receptors. Plants grow roots towards water (not just in all directions until they encounter moisture). Plants also somehow sense heat or wind and close their stomata “so that” they prevent water stress before its onset. Plants “need” pollinators, “so as a result” they produce nectar and develop brightly colored flowers to attract them (not the other way around). Seeds “need” dispersal, so plants develop fruits to attract them, which change color to signal when they are ripe. Viruses regulate their virulence, “in order to” not kill the host they depend on. Animals “need to” defend against pathogens, so there will always be an appropriate antibody ready and waiting. Sweat glands respond independently and secrete sweat “in order to” cool off, not as part of a complex thermoregulatory system involving the hypothalamus, remote sensory cells and hormones. Intentional agency and purpose seems to be everywhere in living systems.

We hope that these many examples help illustrate the ubiquity of teleological imagery, conceptualizations and language throughout biology, not just in evolution. Ultimately, through teleological framing, cells, molecules, organs, species, populations and organisms all become active, purposive agents. They each seem to largely guide their own fate, while contributing (“adaptively,” of course?) to the overall survival and well-being of the organism and the shared ecosystem. We hope that our survey may indicate the scope and depth of the teleology problem for educators.

Of course, in none of these cases does teleology compromise credible scientific research. Biologists learn, through their professional acclimatization, to regard such conceptualizations and language as mere conveniences, or shorthand (Dawkins 2004). The teleological framing is an expedient convention, generally used to help avoid more convoluted phraseology. The challenge for educators, then, lies not merely in instructing (nor possibly misleading) future scientists, but in helping non-biologists achieve a similar level of sophistication and simply recognize these tropes as tropes. In our view, students should thus learn explicitly and reflexively about human cognitive dispositions: how, and perhaps why, we tend to think teleologically, and thus why such teleological frameworks permeate much of biological thought.

Consider J.B.S. Haldane’s famous response when asked what a lifetime spent studying nature can teach us about a Creator: “An inordinate fondness for beetles” (Hutchinson 1959). Even if delivered tongue-in-cheek, Haldane’s quip has resonant staying power because it appeals to our teleological intuitions. It fits our conscious or subconscious expectation that the world unfolds as part of some prescribed plan or purpose. It is difficult for us to imagine that complex natural phenomena (such as nearly half a million described species of beetles) arise spontaneously, without conscious planning on the part of some deliberative agency. We presume that even life itself must have some goal, even if it is merely to reproduce. Yet flames, like beetles, also reproduce. Fire rapidly spreads and conquers just by growing, and with no underlying motive or intent. We can appreciate that fire might arise from wholly material, unplanned causes such as a lightning strike or a piece of burning lava tossed into dry grass by a volcanic ejection. Why do we presume that beetles, or life itself, spreads in any way differently than fire does? Why do we ask “Why are there so many beetles?” when we don’t similarly ask “Why does fire spread so effectively?” Of course, one can easily find people who would in fact argue that hurricanes, earthquakes, and other non-living natural phenomena are just as much the purposeful, teleological handiwork of a deliberate creator as Earth’s multitudes of beetles. Such views, coupled with the many cases throughout biology, from DNA and hormones to ecosystems and body temperature, underlie our orientation to teleology as fundamentally about normative purpose, rather than causality.