Teleology In Biology
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Teleology in biology is the use of the language of goal-directedness in accounts of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
ary adaptation, which some
biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual cell, a multicellular organism, or a community of interacting populations. They usually speciali ...
s and philosophers of science find problematic. The term
teleonomy Teleonomy is the quality of apparent purposefulness and of goal-directedness of structures and functions in living organisms brought about by natural processes like natural selection. The term derives from the Greek "τελεονομία", compoun ...
has also been proposed. Before
Darwin Darwin may refer to: Common meanings * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a territorial capital city i ...
, organisms were seen as existing because God had designed and created them; their features such as eyes were taken by natural theology to have been made to enable them to carry out their functions, such as seeing. Evolutionary biologists often use similar teleological formulations that invoke purpose, but these imply
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
rather than actual goals, whether conscious or not. Dissenting biologists and religious thinkers held that evolution itself was somehow goal-directed ( orthogenesis), and in vitalist versions, driven by a purposeful life force. Since such views are now discredited, with evolution working by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
acting on inherited variation, the use of
teleology Teleology (from and )Partridge, Eric. 1977''Origins: A Short Etymological Dictionary of Modern English'' London: Routledge, p. 4187. or finalityDubray, Charles. 2020 912Teleology" In ''The Catholic Encyclopedia'' 14. New York: Robert Appleton ...
in biology has attracted criticism, and attempts have been made to teach students to avoid teleological language. Nevertheless, biologists still often write about evolution as if organisms had goals, and some philosophers of biology such as Francisco Ayala and biologists such as J. B. S. Haldane consider that teleological language is unavoidable in evolutionary biology.


Context


Teleology

Teleology Teleology (from and )Partridge, Eric. 1977''Origins: A Short Etymological Dictionary of Modern English'' London: Routledge, p. 4187. or finalityDubray, Charles. 2020 912Teleology" In ''The Catholic Encyclopedia'' 14. New York: Robert Appleton ...
, from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
τέλος, ''telos'' "end, purpose" and -λογία, ''logia'', "a branch of learning", was coined by the philosopher Christian von Wolff in 1728. The concept derives from the ancient Greek philosophy of
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical Greece, Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatet ...
, where the final cause (the purpose) of a thing is its function. However, Aristotle's biology does not envisage
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
. Phrases used by biologists like "a function of ... is to ..." or "is designed for" are teleological at least in language. The presence of real or apparent teleology in explanations of natural selection is a controversial aspect of the philosophy of biology, not least for its echoes of natural theology.


Natural theology

Before Darwin, natural theology both assumed the existence of God and used the appearance of function in nature to argue for the existence of God. The English parson-naturalist John Ray stated that his intention was "to illustrate the glory of God in the knowledge of the works of nature or creation". Natural theology presented forms of the teleological argument or argument from design, namely that organs functioned well for their apparent purpose, so they were well-designed, so they must have been designed by a benevolent creator. For example, the eye had the function of seeing, and contained features like the iris and
lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'' ...
that assisted with seeing; therefore, ran the argument, it had been designed for that purpose.


Goal-directed evolution

Religious thinkers and biologists have repeatedly supposed that evolution was driven by some kind of life force, a philosophy known as vitalism, and have often supposed that it had some kind of goal or direction (towards which the life force was striving, if they also believed in that), known as orthogenesis or evolutionary progress. Such goal-directedness implies a long-term teleological force; some supporters of orthogenesis considered it to be a spiritual force, while others held that it was purely biological. For example, the embryologist Karl Ernst von Baer believed in a teleological force in nature, whereas the spiritualist philosopher Henri Bergson linked orthogenesis with vitalism, arguing for a creative force in evolution known as '' élan vital'' in his book '' Creative Evolution'' (1907). The biophysicist Pierre Lecomte du Noüy and the botanist
Edmund Ware Sinnott Edmund Ware Sinnott (February 5, 1888–January 6, 1968) was an American botanist and educator. Sinnott is best known for his work in plant morphology. Career Sinnott received his Bachelor of Arts (1908), Master of Arts (1910), and Doctor of ...
developed vitalist evolutionary philosophies known as '' telefinalism'' and '' telism'' respectively. Their views were heavily criticized as non-scientific; the palaeontologist George Gaylord Simpson argued that Du Noüy and Sinnott were promoting religious versions of evolution. The Jesuit paleontologist Pierre Teilhard de Chardin argued that evolution was aiming for a supposed spiritual " Omega Point" in what he called "directed additivity". With the emergence of the modern evolutionary synthesis, in which the genetic mechanisms of evolution were discovered, the hypothesis of orthogenesis was largely abandoned by biologists, especially with Ronald Fisher's argument in his 1930 book '' The Genetical Theory of Natural Selection''.


Natural selection

Natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
, introduced in 1859 as the central mechanism of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
by
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...
, is the differential survival and reproduction of individuals due to differences in
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...
. The mechanism directly implies evolution, a change in
heritable Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inf ...
traits of a
population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using ...
over time.


Adaptation

A trait which persists in a population is often assumed by biologists to have been selected for in the course of evolution, raising the question of how the trait achieves this. Biologists call any such mechanism the function of the trait, using phrases like "A function of stotting by antelopes is to communicate to predators that they have been detected", or "The primate hand is designed (by natural selection) for grasping." An adaptation is an observable structure or other feature of an organism (for example, an
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
) generated by natural selection to serve its current function. A biologist might propose the
hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can testable, test it. Scientists generally base scientific hypotheses on prev ...
that feathers are adaptations for bird flight. That would require three things: that the trait of having feathers is heritable; that the trait does serve the function of flight; and that the trait increases the fitness of the organisms that have it. Feathers clearly meet these three conditions in living
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
. However, there is also a historical question, namely, did the trait arise at the same time as bird flight? Unfortunately for the hypothesis, this seems not to be so:
theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...
dinosaurs had feathers, but many of them did not fly. Feathers can be described as an exaptation, having been co-opted for flight but having evolved earlier for another purpose such as insulation. Biologists may describe both the co-option and the earlier adaptation in teleological language.


Status in evolutionary biology


Reasons for discomfort

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 for discomfort with teleology among biologists. Firstly, the concept of adaptation is itself controversial, as it can be taken to imply, as the evolutionary biologists
Stephen J. Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Gould sp ...
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 James G. Lennox (born January 11, 1948) is an emeritus professor in the Department of History and Philosophy of Science at the University of Pittsburgh, United States, with secondary appointments in the departments of Classics and Philosophy. He i ...
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 ithout 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
ay be Ay, AY or variants, may refer to: People * Ay (pharaoh), a pharaoh of the 18th Egyptian dynasty * Merneferre Ay, a pharaoh of the 13th Egyptian dynasty * A.Y. (musician) (born 1981), a Tanzanian "bongo flava" artist * A.Y, stage name of Ayo Makun ...
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 Ernest Nagel (November 16, 1901 – September 20, 1985) was an American philosopher of science. Suppes, Patrick (1999)Biographical memoir of Ernest Nagel In '' American National Biograph''y (Vol. 16, pp. 216-218). New York: Oxford University P ...
, 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 Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
. 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, looking at the question of teleology in biology from a Kantian perspective, argues that teleology is important as "a
heuristic A heuristic (; ), or heuristic technique, is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediat ...
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 Teleonomy is the quality of apparent purposefulness and of goal-directedness of structures and functions in living organisms brought about by natural processes like natural selection. The term derives from the Greek "τελεονομία", compoun ...
' 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 The four causes or four explanations are, in Aristotelian thought, four fundamental types of answer to the question "why?", in analysis of change or movement in nature: the material, the formal, the efficient, and the final. Aristotle wrote t ...
, 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." Mayr, Ernst (1974) Boston Studies in the Philosophy of Science, Volume XIV, pages 91–117.


See also

* Fitness landscape * On Truth and Lies in a Nonmoral Sense *
Teleomechanism Rudolf Hermann Lotze (; ; 21 May 1817 – 1 July 1881) was a German philosopher and logician. He also had a medical degree and was well versed in biology. He argued that if the physical world is governed by mechanical laws and relations, then de ...


Notes


References

{{Philosophy of biology Teleology Causality Evolutionary biology Philosophy of biology