exaptation, even within a single article (e.g., Gould, 1991
They are carried along with characteristics that do have
as socialization, learning, and culture as causal explanations ( Tooby &
religion; (b) the causal mechanism responsible for the co-opting (e.g., natural
buy a product on Amazon from a link on here, we get a small percentage of its However, the distinctions should not
sexual ornamentation. They argue that the environment weeding out the less fit individuals is the biggest pressure and driving force behind evolution, keeping only the functionally important traits around. for a new function was an adaptation, selection is required to explain the
(1992). He suggests that universal grammar cannot be derivative and autonomous at the same time, and that Chomsky wants language to be an epiphenomenon and an "organ" simultaneously, where an organ is defined as a product of a dedicated genetic blueprint. in explaining a feature. Steven Pinker and Ray Jackendoff say Chomsky's case is unconvincing. to the growing fetus. She enjoys being in the water much more than being on land. Although Gould (1991)
eyeglasses and laps designed to hold computers, and they grow bald so that they
Over many generations, if it continues to be successful, the
I also discuss the use of the concept of a spandrel in biology. 1987 , subsequent endorsement of this hypothesis). production of offspringwas too narrow to describe the process of evolution by
Although some no doubt succumb to this
1930 ; Morgan, 1896
Webcommerce, and waralthough evolutionary in origin, are incidental spandrels of the large human brain. for many activities that were not part of its original set of functionsplaying
(In C. Crawford, D. Krebs, & M. Smith
Gould and Lewontin werent the first to start the debate between pluralism and adaptationism. (1997a, October 9). The authors outline the conceptual and evidentiary standards that apply to adaptations, exaptations, and spandrels and discuss the relative utility of these concepts for psychological science. problems are filtered out. Gravitational Lensing: What It Is And How It Is Helping Us Discover New Galaxies, Photosynthesis: The Biochemistry Behind How Plants Make Their Food. & J. Tooby (Eds.). Similar the the explanation in chapter one, one can understand an adaptation or natural selection similar to artificial selection. importance and prevalence of adaptations and by-products, all evolutionary
evolved mechanisms that make humans capable of performing the behavior and (b)
do not start to develop until puberty. Exaptations are also explained as adaptations that initially arose through natural selection and were subsequently co-opted for another function (co-opted adaptations), or as features that did not arise as adaptations through natural selection but rather as side effects of adaptive processes and that have been co-opted for a biological function (co-opted spandrels). Organisms can survive for many years, however, and still fail to contribute
without such perturbations. goal. harsh testimony to the changes in selection over time ( Thiessen,
M. (1985). Another confusion lurking in Gould's
"[18] Dunbar found this conclusion odd, and stated that "it falls foul of what we might refer to as the Spandrel Fallacy: 'I haven't really had time to determine empirically whether or not something has a function, so I'll conclude that it can't possibly have one. Webcommerce, and waralthough evolutionary in origin, are incidental spandrels of the large human brain. Noise is
How to improve Bayesian reasoning without instruction:
In fact, these characteristics may
sent to dbuss@psy.utexas.edu. Shepard, R. N. (1984). Language [ edit]. The key point is that all adaptations
cases, according to Gould's primary definition, a mechanism must possess a
proposed two types of func- tional exaptationsadaptations that initially
Gould responded, "The term spandrel may be extended from its particular architectural use for two-dimensional byproducts to the generality of 'spaces left over', a definition that properly includes the San Marco pendentives. In both
predictions and parsimoniously accounting for known empirical findings. Spandrels are byproducts of evolution. The distinction that evolutionary psychologists make between underlying
Cosmides, 1992 ). ). with a function is a spandrel implies that the mechanism was a by-product, and
Lonely hearts
In fact, it can be used as an example of how adaptive explanations can be dismissed even when there is evidence in their favour. A great example of a spandrel lies in one of the triumphal arches located in Rome, Italy, called the Arch of Constantine. ( Tooby and
spandrels mates. Evolutionary psychology: An exchange. Paternal
orgasmic capacities led to the female orgasmic capacities as a side effect. evidentiary burdens of documenting both later co-opted functionality and a
Adaptations and exaptationsin the form of either co-opted adaptations or
Spandrel biological functions to qualify as exaptations, but it seems implausible that
[7], Gould (1991) outlines some considerations for grounds for assigning or denying a structure the status of spandrel, pointing first to the fact that a structure originating as a spandrel through primary exaptation may have been further crafted for its current utility by a suite of secondary adaptations, thus the grounds of how well crafted a structure is for a function cannot be used as grounds for assigning or denying spandrel status. applied evolutionary functional analysis to manifest human behavior, such as in
(In R. D.
originally designed for thermal regulation, may have been co-opted for flying. This example is arguably not an adaptation as it addresses no adaptive problem for the organism, nor does it seem to have a complex design behind its origin. An evolutionary step toward a better solution would be
we show later in this article, understanding the nature of the adaptation
First, an exaptation
(1997a) come away believing that the role of natural selection is somehow
Cooperation and commune longevity: A test of the costly signaling theory of religion. E. O. Wilson (1978) has used this Although the definitions of exaptation quoted verbatim here appear to
DeKay, W. T. & Buss, D. M. (1992). fantasy: An evolutionary psychological approach. mechanisms with each other produce design that is less than might be optimal if
The hollow space in the shells of gastropods (snails) that arises as a consequence of the shell spiraling inwards. Can you list the top facts and stats about Spandrel (biology)? In the first type, features that evolved by
Dickemann, M. (1981). adaptation is, in effect, a probability statement that it is highly unlikely
identification of the adaptation of which it is a by-product and the reason it
functional exaptations, such as the feathers of birds co-opted for flight. Stephen Jay Gould and Richard Lewontin brought the term into biology in their 1979 paper "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme". Heptulla-Chatterjee, S., Freyd, J. J. Learn more about how Pressbooks supports open publishing practices. adaptations, exaptations, spandrels, and functionless by-products. thus helped them to survive. Spandrel (biology It is critical to keep in mind that evolution by natural selection is not
& Cosmides, L.
Spandrel | biology When evolutionists attempt to explain the existence of a
According to this criticism, adaptationists are presumed
but owe their origin
designed to deal with urban living, which currently contains hostile forces far
(e.g., Buss, 1994
However, evolutionary
Spandrel (biology) - Wikiwand current formulations of psychological phenomena ( Buss, 1995
What are Mutations and what are the different types of Mutations? Gould and Lewontin sought to temper what they saw as adaptationist bias by promoting a more structuralist view of evolution. predictions that can then be subjected to testing and potential falsification. considerable value. It was not until the late 1980s, however, that underlying psychological
the mechanism as a species-wide feature. necessary for explaining how functionless by-products are transformed into
(p. 281)\ If all adaptations are exaptations,
Spandrels and trait delimitation: No WebAs a closer example, recently featured in some important biological literature on adaptation, anthropologist Michael Harner has proposed (1977) that Aztec human sacrifice arose as a solution to chronic shortage of meat (limbs of victims were often consumed, but only by people of high status). adaptations ( Buss,
It also provided for the first time a scientific theory to
of an adaptive problem pass through the selective sieve. natural selection or some other causal process, such as an existing human
Tooby, J. humans, sweat glands help to maintain a constant body temperature and thus
& Keefe, 1992 ; Lilienfeld
The
social exchange: Has natural selection shaped how humans reason? Although Dennett's
with men, who do possess the capacity for orgasm for functional reasons (see Symons, 1979
1992 ). At present, however, the evidence for this hypothesis is
; Cosmides,
Spandrels are beautifully explained by Gould as an inevitable by-product of necessary things. 1964 ; Tooby &
As this example illustrates, establishing the hypothesis
formulated and tested. and dreaming. The hump of the great Irish deer is another spandrel. Stephen Jay Gould and Richard Lewontin brought the term into biology in their 1979 paper "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Similar explanations would generally be
getting to those leaves. The University of Washington. does not imply that over time, the concepts of exaptation and spandrels cannot
Both concepts invoke function; therefore, both must meet the
Presumably, averaged over all men through many generations, the
In popular science, natural selection is synonymous with evolution, but that isnt the whole story. scientifically valuable for particular purposes. Spandrel (biology) - Wikiwand Cosmides, L. (1989). Sure, they help humans get along and become the dominant species on the planet, but they might not have started out with that function as its inherent purpose. This behaviour can be seen as a spandrel because What is the "Spandrels" debate about selection. He had ideas behind how species change over time. Environmental tracking by females: Sexual
A similar point holds for an exaptation. modern world, but they are burdened with a Stone Age brain designed to deal with
competing metabolic demands of other mechanisms. Researchers then can empirically test these alternatives. seeks to provide psychologists with a guide to the basic concepts involved in
conceptual and evidentiary standards for invoking function. J. Gelles & J. Once in the population, however, they persist. adaptation that render it less efficient than might be optimal in the absence of
Accordingly, exaptations must be
suggestion to be pluralistic about the conceptual tools of evolutionary
animal behavior, of course, has a long and rich history of success (see Alcock, 1993
The
Psychological foundations of
the current dispute over evolutionary explanations and to clarify the role that
(see, e.g., Nesse, 1990
some other use or no use at all. Spandrels on a Biology Blog benefits of elevated testosterone outweighed its costs in the currency of
In other cases,
The hallmarks of adaptation are features that define special design
must meet evidentiary standards, such as generating specific testable empirical
WebIn evolutionary biology, a spandrel is a phenotypic trait that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. 2. this extent explanations in terms of the past fitness effects of that kind of
with features of the environment during ontogeny (e.g., certain placental
WebAs a closer example, recently featured in some important biological literature on adaptation, anthropologist Michael Harner has proposed (1977) that Aztec human sacrifice arose as a solution to chronic shortage of meat (limbs of victims were often consumed, but only by people of high status). they are not the only products. From vigilance to violence: Tactics of mate retention
tree of descent. What Is The Evolutionary Purpose Of Boredom? These qualities are conceptual criteria subject to empirical testing
WebSpandrels can be as prominent as primary adaptations". [1] Adaptationism is a point of view that sees most organismal traits as adaptive products of natural selection. The key difference is that adaptations are characteristics that are spread through the population because they are chosen through natural selection, whereas exaptations are structures that have already existed in the population and continue to exist in modified variations to make current use of them. responsible for producing the functionless by-products and the existing human
Indeed, theory and research emerging from the study of animal behavior
function. Second, exaptations are "features that now enhance fitness, but were
Religion may simply be the residual of what we as humans have always had; the instinct to survive. future time would still need to be explained in terms of (a) an original
Each finger except the thumb has three bones (called phalanges), which you can see easily when you curl your finger. & Symons, D. (1990). speech production). Euler, H. A. a feature of a species through natural selection because it helped to directly
predators. The easiest spandrel to visualize is the human chin. WebFor example, Kids are likely to have the same religion as their parents. Corrections? each of these concepts. and potential falsification for any particular hypothesis about an adaptation. be useful in generating scientific hypotheses and producing empirical
The genetical evolution of social behavior. responsible for producing the by-product ( Tooby &
capacities, human instrumental actions, or motivational mechanisms, are
As an example of an exaptation, Gould (1991)
Facial asymmetry as an indicator of psychological, emotional, and
Why Are There 24 Hours In A Day And 60 Minutes In An Hour? Biology & Philosophy, 19(5), 655-686. doi:10.1007/s10539-005-5568-6. Stephen Jay Gould and Richard Lewontin brought the term into biology in their 1979 paper "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist (1966) . If this is a description of the term as is used presently, it needs to be contrasted with the original formulation of the idea by Gould and Lewontin. Similarly, it might, in principle, be advantageous for humans to
advertisements reflect sexually dimorphic mating strategies. particular constellation of findings, a specific hypothesis that a feature is an
through natural selection but rather as side effects of adaptive processes and
B. S. (1989). ). fitness. costsand these costs impose constraints on the optimal design of adaptations. evolutionary perspective. Proceedings of the National Academy of Sciences. All invoke function. Obviously, a characteristic cannot be explained by
These two easily
attributes produce more offspring, on average, than those lacking these
successful solution to a specific adaptive problem, the alternative hypotheses
clarity, it is critical to distinguish between exaptation, as Gould (1991)
Many adaptations develop long after
The easiest spandrel to visualize is the human chin. people use their hands to grip a tennis racquet, for example, this
WebExamples of spandrels [ edit] Human chin [ edit]. Gould, S. J. 3
Bellis, 1995 ; Buss, 1988
; Romanes,
They are used to display complex imagery and art that serves to elevate the aesthetic value of the building. lability. Stanford University, (1998) Adaptations, Exaptations, and Spandrels. evolutionary theory, we hope that this article will serve as a guide to some of
(1991) concept of exaptation can be meaningfully distinguished from
to produce speech. & Cicchetti, 1993 ; Sedikedes
Obviously, the inheritance of selected characteristics and their spread
the study of fixed action patterns (e.g., Lorenz, 1952
Or they can be even more indirect, such as when a person helps a brother
1951 ) and universals of facial expression ( Ekman, 1973
changes would have to be coordinated with other changes, such as a musculature
to solve it. Cooperation is more the thing of focus in this case and so be must discredit religion as an exaptation. particular forms they do. Without the need to coordinate design for running with design for
explanatory concepts. What Are Cobwebs? Consider the human hand as an adaptation. could try to disconfirm all existing functional explanations and could try to
On the use and misuse of Darwinism
The bone in the forelimb has adapted to perform a function similar to that of an opposable thumb. Take your own here and learn something new and perhaps surprising. 1966 ). in press ). Ekman, P. (1973). current function. exaptation encounters the same problem that Gould (1991)
The concepts of adaptation and natural selection are
Cosmides, L. & Tooby,
Recently, Stephen J.
This example is arguably not an adaptation as it addresses no adaptive problem for the organism, nor does it seem to have a complex design behind its origin. The first example is based on the human hand. Is Mathematics An Invention Or A Discovery? novel challenge to survival of candle flames. Daly, M. (1992). evolve X-ray vision to see what is on the other side of obstacles or telescopic
conditions, or other intuitive notions of well-being. Although all three invoke selection, adaptations that
Gender differences in receptivity to sexual offers. Cosmides, 1992 ). psychology. speed in women, therefore, presumably occurs because of compromises required by
In fact, it can be used as an example of how adaptive explanations can be dismissed even when there is evidence in their favour. there. selected features (adaptations), by-products of naturally selected features, and
Linguist Noam Chomsky and Gould himself have both argued that human language may have originated as a spandrel. Evolutionary
mechanism that enable it to perform the new exapted function: "Exaptations
(In J. H. Barkow, L.
adaptive problem. supporting a by-product hypothesis generally requires specifying the adaptation
inclusive fitness. useful characteristics did not arise as adaptations . & Lewontin, R. C. (1979). Just as with a
A naturally occurring example of a by-product of adaptation is the human
psychological phenomena. characteristics or the reproduction of the individuals' genetic relatives ( Dawkins,
various usages of the term exaptation. Lightbulbs also
Pinker, S. (1997a, October 9). Selection played a role in the evolution of the human chin. exaptation would be more appropriate for describing the current
Wakefield, J. C. (in press). Because these byproducts of adaptations that had no real relative advantage to survival, they were termed spandrels. Spandrel The departure from optimal design for running
feet). If this is a description of the term as is used presently, it needs to be contrasted with the original formulation of the idea by Gould and Lewontin. variation, along with other constraints, has apparently precluded such
A common misconception surrounding adaptations is that traits that are chosen for are embedded into the genetic code of a species, which would make it possible to produce offspring that will carry the trait of choice. WebSpandrels can be as prominent as primary adaptations". hypotheses regarding human psychological mechanisms is much more recent, and
co-opted from previous structures that evolved for reasons different from those
This means that the spandrel isnt an adaptation to anything in the environment. qualities, such as language, are merely incidental by-products of large brains
From "learning" to parameter setting in biology and the study of language. The term "spandrel" originates from architecture, where it refers to the roughly triangular spaces between the top of an arch and the ceiling. [12] In this view, Chomsky initially pointed to language being a result of increased brain size and increasing complexity, though he provides no definitive answers as to what factors may have led to the brain attaining the size and complexity of which discrete infinity is a consequence. Biologically functionless uses
feature, they must do so by reference to its evolutionary history. 1997. Our editors will review what youve submitted and determine whether to revise the article. Exaptations, in contrast, exist in the present because they were
Exaptation: A crucial tool for evolutionary
more dangerous to human survival (e.g., cars, electrical outlets) but for which
Exaptation-A missing term in the science of form. and (e) Is the proposed
Tin-Nu-Swe, , Phillips, R. E. & Warrell, D. A. facial features, and the commencement of sexual interest and activity. ; Tinbergen,
for thermal regulation but subsequently co-opted for flight, it is clearly
ScienceABC participates in the Amazon Human nature, individual
Hypotheses about functionless by-products must meet rigorous scientific
Each adaptation has its own period of evolution. Gould, S. J., &Vrba, E. S. (1982). humans lack evolved mechanisms of fear preparedness ( Mineka, 1992
Pinker, S. & Bloom, P. (1992). Gigerenzer, G. &
Evolutionary versus Roschian analyses of
Linguist Noam Chomsky and Music [ edit]. this emerging perspective. ", "The Faculty of Language: What's Special About It? what the concepts actually mean, and how they should be applied. Table 3. is no difference, and we believe that there is utility in differentiating
Selection requires that each step and each intermediate form in the
Technically, inclusive fitness is not a property of an individual organism
How to live without a heart or a brain - Lessons from a Jellyfish. Beauty is in the adaptations of the
Webover the past 40 years there are virtually no examples of spandrels in the primary literature. in press ). used the large size of the human brain and its function of enabling humans
psychologists and biologists are generally interested in explaining existing
The key issue is not whether a hypothesis is a story
evolutionary explanations of the existence of species-wide mechanisms are to
development of evolutionary psychology as hypotheses to be subjected to
Proceedings of the National Academy of Sciences. Second, the researchers could formulate an
actions have on the reproductive success of his or her genetic relatives,
named after Voltaire's
biological motion. Medin (Ed.). Indeed, theory and research emerging from the study of animal behavior
The concept of biological spandrelsincluding the examples here given of masculinized genitalia in female hyenas, exaptive use of an umbilicus as a brooding chamber by snails, the shoulder hump of the giant Irish deer, and several key features of human mentalityanchors the critique of overreliance upon adaptive scenarios in fitness of its bearer to qualify as an exaptation. These 'Useless' Quirks of Evolution Are Actually Evidence It's Still value for psychological science. For conceptual
WebIn evolutionary biology, a spandrel is a phenotypic trait that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. (1991). Lack of available genetic variation imposes a third constraint on optimal
Webover the past 40 years there are virtually no examples of spandrels in the primary literature. brain) is critical to the analysis. produced the incidental by-product. Darwinians, what's the fuss about? identify how the known mechanisms for development of naturally selected male
point of view to merely present a long speculative list of purported
This is not true as it implies that genotype of an organism is the sole contributor of behavioural and psychological features as well. over time. This example is arguably not an adaptation as it addresses no adaptive problem for the organism, nor does it seem to have a complex design behind its origin. 1995 ; Williams,
Women, for example, have been selected both for bipedal
Evolutionary psychology
nutrients, aspects of parental care) are critical for the reliable development
hypothesized function, co-opted exaptations and spandrels carry the additional
should be subjected to reasonable standards of hypothesis formulation and
that are responsible for the emergence of an adaptation ( Tooby &
A belief of ghosts/afterlife generated by a mechanism producing illusory, but adaptive beliefs. The existence in humans of a
feature might be explained. Each finger except the thumb has three bones (called phalanges), which you can see easily when you curl your finger. & Karter, A. J. are incidental by-products. Most adaptations, of course, are not caused by single genes. This is not because of gene transmission, but the features still got passed down. hypothesized to occur long before Charles
two standard pillars of evolutionary biologynatural selection and
there be a current function, any more than the use of adaptation requires such a
Darwin's task was more difficult than it might appear at first. mechanisms, such as those postulated by cognitive psychologists subsequent to
But the lack of available genetic
It provides the raw
selective-breeding attempts to do this have failed, presumably because cattle
selective pressures. humans to exploit such capabilities. hypothesis for which data are currently lacking? The man who mistook his wife for a chattel. Evolutionary psychology is emerging as a promising theoretical perspective
Buss, D. M., Haselton, M. G., Shackelford, T. K., Bleske, A. L., & Wakefield, J. C. (1998). [12][13] Chomsky writes that the language faculty, and the property of discrete infinity or recursion that plays a central role in his theory of universal grammar (UG), may have evolved as a spandrel. production of light and are part of its functional design. co-opted adaptation to describe this first category. P. R. Abramson & S. D. Pinkerton (Eds. Differential reproductive success, by virtue of the possession of
Filial Cannibalism: Why Do Animals Sometimes Kill And Eat Their Own Young? Both traits that we know are desirable during mate selection. moment, whether or not they operated in the past. offspring. The empirical application of evolutionary ideas to the study of nonhuman
In summary, evolutionary functional analysis is useful regardless of whether
standards. The bone in the forelimb has adapted to perform a function similar to that of an opposable thumb. Cosmides, 1990b ), unless such correlations reveal longer term, past
(1994). It is carried
Omissions? problem ( Cosmides
evidentially compelling than competing hypotheses? ). facilitate the functioning of, other evolved mechanisms. According to this argument, some evolutionary biologists and
Spandrel ; Cosmides,
arose de novo from mutations invoke selection in the original construction of
WebIn evolutionary biology, a spandrel is a phenotypic trait that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection. Instead of continuing to contribute more findings on human adaptive traits he chose to shine a light of areas not yet considered. 1859/1958 ) as well as how others vanish. Third, developmental events may
(1991). in married couples. Consequently, relative to initial adaptations,
One well-studied example is seen in an island-dwelling population of Italian wall lizards ( Podarcis sicula ), which spend less time basking in the sun than their mainland cousins. and, moreover, contributes to the reproductive success of genes specifically for
of these options they pursue. This process of
correlations will continue to be obtained in future generationsa questionable
Spandrels on a Biology Blog embody the pluralism advocated (e.g., Tooby &
personal happiness, well-being, or the ability to adjust to changing conditions
1997 , for a testable exaptation hypothesis about the origins of human
an understanding of the evolved cognitive and motivational mechanisms that led
exaptation, consistent with the above quoted definitions, to refer only
Define and compare adaptations, exaptations and spandrels. Gould, S. J. Spandrels against toxins. Haig, D. (1993). This behaviour can be seen as a spandrel because & Gattiker, U. E. (1991). Human Cognition: Are We Really Blank Slates? & Weitzel, B. for fatty foods to ensure adequate caloric intake is no longer fitness-enhancing
(1997b). lacking rigorous standards for hypothesis formulation and evidentiary
birds first having evolved for thermal regulation but then later co-opted for
function is eternal; if you go back far enough, you will find that every
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