Teleology in biology

Status in evolutionary biology

A problematic issue

Apparent teleology is a recurring issue in evolutionary biology, much to the consternation of some writers, and as an explanatory style it remains controversial. There are various reasons why biologists may find teleology problematic.

Firstly, the concept of adaptation is itself controversial, as it can be taken to imply, as the evolutionary biologists Stephen J. Gould and Richard Lewontin argued, that biologists agree with Voltaire's Doctor Pangloss in his 1759 satire Candide that this is "the best of all possible worlds", in other words that every trait is perfectly suited to its functions. However, all that evolutionary biology requires is the weaker claim that one trait is at least slightly better in a certain context than another, and hence is selected for.

Secondly, teleology is linked to the pre-Darwinian idea of natural theology, that the natural world gives evidence of the conscious design and beneficent intentions of a creator, as in the writings of John Ray. William Derham continued Ray's tradition with books such as his 1713 Physico-Theology and his 1714 Astro-Theology. They in turn influenced William Paley who wrote a detailed teleological argument for God in 1802, Natural Theology, or Evidences of the Existence and Attributes of the Deity collected from the Appearances of Nature, starting with the watchmaker analogy. Such creationism, along with a vitalist life-force and directed orthogenetic evolution, has been rejected by most biologists.

Thirdly, attributing purposes to adaptations risks confusion with popular forms of Lamarckism where animals in particular have been supposed to influence their own evolution through their intentions, though Lamarck himself spoke rather of habits of use, and the belief that his thinking was teleological has been challenged.

Fourthly, the teleological explanation of adaptation is uncomfortable because it seems to require backward causation, in which existing traits are explained by future outcomes; because it seems to attribute the action of a conscious mind when none is assumed to be present in an organism; and because, as a result, adaptation looks impossible to test empirically.

A fifth reason concerns students rather than researchers: Gonzalez Galli argues that since people naturally imagine that evolution has a purpose or direction, then the use of teleological language by scientists may act as an obstacle to students when learning about natural selection. Such language, he argues, should be removed to make teaching more effective.

Removable teleological shorthand

Statements which imply that nature has goals, for example where a species is said to do something "in order to" achieve survival, appear teleological, and therefore invalid to evolutionary biologists. It is however usually possible to rewrite such sentences to avoid the apparent teleology. Some biology courses have incorporated exercises requiring students to rephrase such sentences so that they do not read teleologically. Nevertheless, biologists still frequently write in a way which can be read as implying teleology, even though that is not their intention. John Reiss argues that evolutionary biology can be purged of apparent teleology by rejecting the pre-Darwinian watchmaker analogy for natural selection; other arguments against this analogy have also been promoted by writers such as the evolutionary biologist Richard Dawkins.

Some philosophers of biology such as James G. Lennox have argued that Darwin was a teleologist, while others like Michael Ghiselin described this claim as a myth promoted by misinterpretations of his discussions, and emphasized the distinction between using teleological metaphors and actually being teleological. Michael Heads, on the other hand, describes a change in Darwin's thinking about evolution that can be traced from the first volume of On the Origin of Species to later volumes. For Heads, Darwin was originally a far more teleological thinker, but over time, "learned to avoid teleology." Heads cites a letter Darwin wrote in 1872, in which he downplayed the role of natural selection as a causal force on its own in explaining biological adaptation, and instead gave more weight to "laws of growth," that operate [without the aid of natural selection].

Andrew Askland, from the Sandra Day O'Connor College of Law claims that unlike transhumanism, an ideology that aims to improve the human condition, which he asserts is "wholly teleological", Darwinian evolution is not teleological.

Various commentators view the teleological phrases used in modern evolutionary biology as a type of shorthand for describing any function which offers an evolutionary advantage through natural selection. For example, the zoologist S. H. P. Madrell wrote that "the proper but cumbersome way of describing change by evolutionary adaptation [may be] substituted by shorter overtly teleological statements" for the sake of saving space, but that this "should not be taken to imply that evolution proceeds by anything other than from mutations arising by chance, with those that impart an advantage being retained by natural selection."

Irreducible teleology

Other philosophers of biology argue instead that biological teleology is irreducible, and cannot be removed by any simple process of rewording. Francisco Ayala specified three separate situations in which teleological explanations are appropriate. First, if the agent consciously anticipates the goal of their own action; for example the behavior of picking up a pen can be explained by reference to the agent's desire to write. Ayala extends this type of teleological explanation to non-human animals by noting that "A deer running away from a mountain lion ... has at least the appearance of purposeful behavior." Second, teleological explanations are useful for systems that have a mechanism for self-regulation despite fluctuations in environment; for example, the self-regulation of body temperature in animals. Finally, they are appropriate "in reference to structures anatomically and physiologically designed to perform a certain function."

Ayala, relying on work done by the philosopher Ernest Nagel, also rejects the idea that teleological arguments are inadmissible because they cannot be causal. For Nagel, teleological arguments must be consistent because they can always be reformulated as non-teleological arguments. The difference between the two is, for Ayala, merely one of emphasis. Nagel writes that while teleological arguments focus on "the consequences for a given system of a constituent part or process," the equivalent non-teleological arguments focus on ""some of the conditions ... under which the system persists in its characteristic organization and activities." However, Francisco Ayala argued that teleological statements are more explanatory and cannot be disposed of. Karen Neander similarly argued that the modern concept of biological 'function' depends on natural selection. So, for example, it is not possible to say that anything that simply winks into existence, without going through a process of selection, actually has functions. We decide whether an appendage has a function by analysing the process of selection that led to it. Therefore, Neander argues, any talk of functions must be posterior to natural selection, function must be defined by reference to the history of a species, and teleology cannot be avoided. The evolutionary biologist Ernst Mayr likewise stated that "adaptedness ... is an a posteriori result rather than an a priori goal-seeking."

Angela Breitenbach, from a Kantian perspective, argues in Kant Yearbook that teleology in biology is important as "a heuristic in the search for causal explanations of nature and ... an inevitable analogical perspective on living beings." In her view of Kant, teleology implies something that cannot be explained by science, but only understood through analogy.

Colin Pittendrigh coined the similar term 'teleonomy' for apparently goal-directed biological phenomena. For Pittendrigh, the notion of 'adaptation' in biology, however it is defined, necessarily "connote that aura of design, purpose, or end-directedness, which has, since the time of Aristotle, seemed to characterize the living thing." This association with Aristotle, however, is problematic, because it meant that the study of adaptation would inevitably be bound up with teleological explanations. Pittendrigh sought to preserve the aspect of design and purpose in biological systems, while denying that this design can be understood as a causal principle. The confusion, he says, would be removed if we described these systems "by some other term, like 'teleonomic,' in order to emphasize that the recognition and description of end-directedness does not carry a commitment to Aristotelian teleology as an efficient causal principle." Ernst Mayr criticised Pittendrigh's confusion of Aristotle's four causes, arguing that evolution only involved the material and formal but not the efficient cause. Mayr proposed to use the term only for "systems operating on the basis of a program of coded information."

William C. Wimsatt affirmed that the teleologicality of the language of biology and other fields derives from the logical structure of their background theories, and not merely from the use of teleological locutions such as "function" and "in order to". He stated that "To replace talk about function by talk about selection ... is not to eliminate teleology but to rephrase it". However, Wimsatt argues that this thought does not mean an appeal to backwards causation, vitalism, entelechy, or anti-reductionist sentiments.

The biologist J. B. S. Haldane observed that "Teleology is like a mistress to a biologist: he cannot live without her but he's unwilling to be seen with her in public."