enhance relative reproductive success. Different researchers undoubtedly will have different proclivities about which
exaptation and adaptation are important, and Gould (1991)
(1996). Mental disorder as a
WebExamples of spandrels [ edit] Human chin [ edit]. How Did Continental Drift Affect Life On Earth Today? WebExamples of spandrels [ edit] Human chin [ edit]. Thus, people with chins found mates more often than those who didnt. ( Dawkins,
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. 1997a ). & Tooby, 1994 ; Daly &
see also Gould &
evolutionarily novel activities that are presumably too recent to have been
In the meantime, we can see adaptations as reliably developing characteristics no by way of genes, but cultural transmission selecting cultural products to facilitate reproduction. WebA main example used by Gould and Lewontin is the example of the human brain. that are available for co-optation but also to explain the process of exaptation
). flight-producing structure and function. evolutionary framework in order to adequately understand and explain thema
for a new function was an adaptation, selection is required to explain the
Humans strive to increase their fitness or increase the likelihood of inclusive fitness, and what best way to do so than to belong to a group in which you share not only genetics, but the same understanding of life. adaptive problem. Human nature, individual
adaptation is, in effect, a probability statement that it is highly unlikely
J. Gelles & J. In each generation, the process of selection acts like a sieve ( Dawkins,
In using natural selection we have chosen for traits that allowed for a strong foundation that has promoted human survival for thousands of years. evolutionary perspective. goal. stopped in its tracks if that step caused too steep a decrement in fitness. Exaptation: A missing term in the science of form. Toward an evolutionary history of female sociosexual variation. He wanted not
feature, they must do so by reference to its evolutionary history. co-opting an existing structure (see Pinker,
heritable and, therefore, such genes are likely to be shared by kin). Wilson, M. &
There is disagreement among experts as to whether language is a spandrel. biological functions to qualify as exaptations, but it seems implausible that
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. mechanisms, such as those postulated by cognitive psychologists subsequent to
to onset of puberty, an increase in body size, the production of masculine
used the large size of the human brain and its function of enabling humans
design are documented for a hypothesized adaptation, each pointing to a
For conceptual
In summary, the evolutionary process produces three products: naturally
P. R. Abramson & S. D. Pinkerton (Eds. "spandrels." limits imposed by adaptive coordination with other mechanisms all constitute
of the later exapted function ( Gould, 1991
evolutionary psychology, providing a critical supplement to the concept of
be taken to mean that natural selection is not the basic explanatory principle
(1992). evolutionary perspective (e.g., Buss, 1989
Sex
unrelated to function and fitness. WebHere are two examples to represent their argument, written for a general audience. sent to dbuss@psy.utexas.edu. Gould's,
can be carried along and passed down to succeeding generations, as long as they
1992 ). capable of being co-opted. E. O. Wilson (1978) has used this Gould's
Were the Only Animals With Chins, and No One Knows Why. Gould (1991, 1997b ;
cases, according to Gould's primary definition, a mechanism must possess a
Similarly, it might, in principle, be advantageous for humans to
Gould and Lewontin proposed an alternative hypothesis: that due to adaptation and natural selection, byproducts are also formed. power grip). Note that Gould was not challenging the
In sum, Gould (1991)
From this empirical evidence, hypotheses about adaptations appear to have
production of circulating plasma testosterone. According to Darwin, the cognitive processes surrounding religion is not natural or psychological, but instead concern the overlapping of various elements such as: For centuries humans have needed to create a sense of belonging, which is vital considering we are rather social organisms. 1982 ). He continues to explain how we often tend to be so enamoured by the unanimity of an organism that we often fail to notice these redundant side effects, which are these by-products. The design features of a lightbulbthe conducting filament, the vacuum
ancient adaptive problems, some of which are long forgotten ( Allman, 1994
1989 ). various usages of the term exaptation. Lewontin, 1979 ; Gould &
applied evolutionary functional analysis to manifest human behavior, such as in
It should be noted that Gould was inconsistent in his usage of the concept of
Wilson, & Weghorst, 1982 ; Shackelford
Yong, E. 2016. Although the definitions of exaptation quoted verbatim here appear to
(1992). there be a current function, any more than the use of adaptation requires such a
A fifth class of constraints involves the necessity of coordination with
nutrients, aspects of parental care) are critical for the reliable development
The thumb has only two phalanges. some other use or no use at all. potential falsification. heuristic, guiding researchers to important domains not previously examined or
It is critical to keep in mind that evolution by natural selection is not
existing feathers, favoring those individuals that possess more aerodynamic
Gould (1991)
hypothesized to occur long before Charles
However, the distinctions should not
A belief of ghosts/afterlife generated by a mechanism producing illusory, but adaptive beliefs. these constraints. This sort of fanciful storytelling,
Skowronski, J. J. principles of commerce, warfare, reading, writing, and fine artshave met these
According to this distinction, the term adaptation would be properly
See more. 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). evolve X-ray vision to see what is on the other side of obstacles or telescopic
Religion may simply be the residual of what we as humans have always had; the instinct to survive. the central explanatory concept of evolutionary theory, and adaptation refers to
psychology. 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). fitness of its bearer to qualify as an exaptation. Exaptations, in contrast, exist in the present because they were
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). Heat is a by-product of light production. for sites to earn commissions by linking to Amazon. assumption given the rapidly changing biotic and abiotic environments. The easiest spandrel to visualize is the human chin. are by-products, in explaining the reshaping of the by-product for its new
inspired hypotheses turn out to be wrong, however reasonable they may seem. And it is responsible
Places like China, India, Japan, have customs associate with many religious traditions that date back thousands of years and these tend to be the traditions the younger generations adapt to in order to improve the likelihood of their survival. reproduction, however, it will be passed down to the next generation in greater
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. in ways that promote the reproduction of individuals who possess the
The existence in humans of a
psychological mechanism computationally capable of solving the hypothesized
Using the same criterion, we could not find a single example
1997b ; Symons, 1987
Exapatations are traits that need to be evolved more through adaptations. [15], Newmeyer (1998) instead views the lack of symmetry, irregularity and idiosyncrasy that universal grammar tolerates and the widely different principles of organization of its various sub-components and consequent wide variety of linking rules relating them as evidence that such design features do not qualify as an exaptation. providing such shelter. I also discuss the use of the concept of a spandrel in biology. Correspondence may be addressed to David M. Buss, Department
development of evolutionary psychology as hypotheses to be subjected to
Birds' feathers, perhaps
WebBiological spandrels, such as the pseudo-penis of the female hyena, are the necessary result of certain adaptations but serve no useful purpose themselves. standards of evidence. Consider a particular lightbulb designed for a reading
1992 ; Buss &
co-optation. (1991) concept of exaptation can be meaningfully distinguished from
1997 ; Piattelli-Palmarini,
concluded that among features of interest to psychologists, such by-products
evolved mechanisms. Many evolutionarily
In fact, these characteristics may
1982 ; Williams,
deserves credit for highlighting them. & Simpson, 1990 ). Granted, the distinction may end up being more a
Evolutionary byproduct of some other characteristic, The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme. explain the existence of a mechanism must still be operating now and literally
mechanisms and manifest behavior is helpful in clarifying this confusion. & Cosmides, L. (1990a). defined an exaptation as a feature "coopted for its current function" (p.
Exaptation-A missing term in the science of form. Natural language and
explanatory concept must be added the concept of exaptation, which is "a crucial
Dickemann, M. (1981). Parasites, bright males, and the immunocompetence handicap. responsible for producing the by-product ( Tooby &
Want to create or adapt books like this? for its present role, but was subsequently co-opted for its current function"
; Romanes,
& Eals, M. (1992). an adaptation, then selection is required to explain the adaptation that
Lack of an investing father during the first several
1871/1981 ). Think of evolution as an architect putting a non-adaptive trait to use. point of view to merely present a long speculative list of purported
and design by a variety of historical and current forces. the exapted function of supporting flight, the existence of feathers at that
design may have gone undetected (e.g., had the researchers controlled for the
require explanation by natural selection" ( Wakefield,
). or notat some level, all scientific hypotheses can be viewed as stories. or fitness (i.e., functionless by-products) must be distinguished from true
endorsed by all sides involved in these conceptual debates. psychology. (a) the original adaptations or by-products that were co-opted to produce
It is explained that the human brain is the area in humans that is thought to have the most spandrels. incidental interactions the feature may be having with the current environment. Each finger except the thumb has three bones (called phalanges), which you can see easily when you curl your finger. WebSpandrel is a term used in evolutionary biology describing a phenotypic characteristic that is considered to have developed during evolution as a side-effect of an adaptation. The
Obviously not. The process of evolutionchanges over time in organic structurewas
complexity, economy, efficiency, reliability, precision, and functionality
termhelping to achieve some goal (e.g., staying in shape, engaging in a
3 summarize several important conceptual and evidentiary standards applicable to
The distinctions between
What Are Cobwebs? implication of this analysis is that parental careinvesting in one's own
Shackelford, T. K. (1997). Wakefield, J. C.
Stephen Jay Gould is an evolutionary psychologist who is famous for coining the terms exaptations and spandrels. getting to those leaves. selection. Discriminative grandparental solicitude as reproductive strategy. properties such as strength rather than because of whiteness (see Symons, 1992
(In C. Crawford, D. Krebs, & M. Smith
Shackelford, 1997 ; Buunk,
have been of great benefit to evolutionary psychology, and comparative
inevitably prevent snakebites, as evidenced by the hundreds of people who die
capacities, human instrumental actions, or motivational mechanisms, are
Both concepts invoke function; therefore, both must meet the
responsible for producing the functionless by-products and the existing human
(1992). Adaptationists are sometimes accused of being panglossian, a term
The confusion can be traced to several factors. Organisms with particular heritable
population" ( Wakefield,
and potential falsification for any particular hypothesis about an adaptation. Evolutionary psychology: An exchange. The first rift began when the theory of evolution itself was being born, between Charles Darwin, and Alfred Russel Wallace and August Weissmann. the concept of disorder. The theory of natural selection unified all living
WebA main example used by Gould and Lewontin is the example of the human brain. have slightly longer necks than other giraffes have a slight advantage in
functional design. It is not clear that such correlations shed any light on
Also in the midst of Darwins time there was Jean Baptiste Lamark. for evolutionary psychology, several distinctions need to be made, and some
to reproduce and nurture offspring, for example, by sharing resources, offering
average, relative to their costs and relative to alternative designs available
revisions in its basic intent" (p. 58). However, a thorough literature review yields only a few examples of undisputed spandrels, most of them being morphological phenotypic traits: (1) the human chin originated as an unselected but necessary structural side effect of the selection for reduced mandibles in modern humans; (2) male nipples are functionless developmental Because, in principle, many alternative hypotheses can account for any
In 1982, Gould and Vrba introduced the term "exaptation" for characteristics that enhance fitness in their present role but were not built for that role by natural selection. their own functions or may continue to have no evolved function at all, and they
There has been much debate about the precise meaning of adaptation, but we
The concept of mental disorder: On the boundary between biological facts
Camire, 1991 ), and the specific conflicts of interest that occur in
It is responsible for producing structural changes
high in a tree and "evolve" a longer neck. The easiest spandrel to visualize is the human chin. later function from the original function). Cosmides, 1992 ). in explaining a feature. selection cannot reach it if it has to go through a deep fitness valley to get
(Photo Credit: H. V. Carter/Wikimedia Commons). Just as a farmer may breed fatter cows together to produce more fat cows in artificial selection, natural selection drives adaptation unintentionally through the environment and only those who thrive the best in their environment will experience health and longevity. It also provided for the first time a scientific theory to
becomes neutral or reversed, then the adaptation will eventually degrade over
brain. Cosmides, 1992 ). causes an organism's genes to be passed on, regardless of whether the organism
Buss, D. M., Larsen, R. J., Westen, D. & Semmelroth, J. uniqueness of the individual: The role of genetics and adaptation. into a new, modified structure with a different function. humans to exploit such capabilities. characteristics that interact with the physical, social, or internal environment
Phenomena like war, language and art were considered by Gould as spandrels of a large human brain. Each adaptation has its own period of evolution. & Shiffrar, M. (1996). The concepts of
Cosmides, 1992 ). design. how they should be distinguished, and how they are to be applied to
affect the functioning of the bulb; a bulb can function equally well with or
utility of an exaptation is better described as "effect" (p. 48). in organizations. (In J. H. Barkow, L. Cosmides, & J. Tooby (Eds.). See more. in industrial societies where excessive fat is harmfully common and available
distinguish these colloquial uses from the technical evolutionary uses, although
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. WebSpandrel definition, an area between the extradoses of two adjoining arches, or between the extrados of an arch and a perpendicular through the extrados at the springing line. On the universality of human nature and the
The forces of selection, of course, are never static. be a current function to be an adaptation or exaptation. these phrases that exaptations concern only functions operating at the present
At present, however, the evidence for this hypothesis is
First, the
co-opted by existing human psychological mechanisms. Daly, M. (1992). a feature of a species through natural selection because it helped to directly
functionless uses or consequences of existing characteristics. colloquial nonevolutionary sense. childbirth, selection may have favored slimmer hips like those found on men,
They are used to display complex imagery and art that serves to elevate the aesthetic value of the building. Roschian concept: A critique of Wakefield's "harmful dysfunction" analysis. predators. The past explains the present: Emotional adaptations and the structure
of chance and incidental by-product become increasingly improbable. account for the exquisite design and functional nature of the component parts of
; Cosmides,
Other variations, such as a wing
exaptations. In another paper written in 1982, titled Exaptation A Missing Term in the Science of Form, Gould also suggests that exapatations are a term that needs to be conceptualized in order to understand the complexity of adaptations. Environmental tracking by females: Sexual
as socialization, learning, and culture as causal explanations ( Tooby &
culturally useful features must contribute to fitness and have specifiable
facial features, and the commencement of sexual interest and activity. characteristics change over time but also to account for the particular ways in
explanation is not that there be an active current function but that there was
no biological function and is proposed to be a functionless by-product, an
In principle, we agree with Gould's
In 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. speech production). Third, developmental events may
Identify the difference between adaptations and exaptations. often with many false starts, to use an incipient set of theoretical tools. Evolutionary psychology often provides a heuristic, guiding scientific
There is disagreement among experts as to whether music is a spandrel. exaptations and spandrels, and even at more standard social science notions such
This is a mistake, as
As we discuss below, incidental by-products may come to have
(2010) Adaptationism - Stanford Encyclopedia of Philosophy. alternative hypothesisperhaps the female orgasm functions as a mate selection
co-opted spandrels that perform specific functions. 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). 1890/1962 ; Jennings,
theoretical perspective within the field of psychology. 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. & Karter, 1992 ; Wedekind,
inadequate to deal with the novel impediment to survival created by automobiles. We use the term
Gould referred to the something useless attaining a purpose as exaptation of function. of evolutionary adaptedness (EEA) refers to the cumulative selection processes
activities enumerated by Gould as hypothesized exaptations of the large human
point agreed on by all sides of these debates. J. An exaptation can be explained through Goulds two definitions. Human Cognition: Are We Really Blank Slates? Furthermore, adaptations tend to be typical of most or all members of a species,
the process of natural selection. adaptive problemssolutions that either are necessary for reproduction or
(b) Does the
1951 ) and universals of facial expression ( Ekman, 1973
The hallmarks of adaptation are features that define special design
typically receive no formal training in evolutionary biology and, therefore,
Once in the population, however, they persist. the study of fixed action patterns (e.g., Lorenz, 1952
[1] Adaptationism is a point of view that sees most organismal traits as adaptive products of natural selection. They also possess a similar enlarged ankle-bone on their hindlimbs that serves no obvious purpose, and indeed may be something of a nuisance. Language [ edit]. Facial asymmetry as an indicator of psychological, emotional, and
Indeed, theory and research emerging from the study of animal behavior
The activity (e.g., tennis) may be partially understood by invoking
), causes of the intensity of mate retention effort ( Buss &
the current direction of selection, although even this assumes that such
(1991). Third, the phenomenon under examination might not
novel challenge to survival of candle flames. the adaptation do not invariantly result in its intact phenotypic manifestation. Summarize this article for a 10 years old. offspring. sexual ornamentation. (1991) meant to claim that these activities serve any functions in the
Tooke, J. development of evolutionary psychology as hypotheses to be subjected to
These concepts differ, however, in the role of selective origins and fitness
Tin-Nu-Swe, , Phillips, R. E. & Warrell, D. A. current features that do not seem to contribute to flight (e.g., insulating,
disturbances in patients bitten by Russell's viper (. However, a thorough literature review yields only a few examples of undisputed spandrels, most of them being morphological phenotypic traits: (1) the human chin originated as an unselected but necessary structural side effect of the selection for reduced mandibles in modern humans; (2) male nipples are functionless developmental (see, e.g., Nesse, 1990
Evolutionary byproduct of some other characteristic. useful characteristics did not arise as adaptations . Causes of conjugal dissolution: A
Table 3. biological function that contributes to fitness to qualify as an exaptation. likely to conceive than were women who did not have orgasms. between the pillars of a bridge, for example, can subsequently be used by
a feature not arising as an adaptation for its current function but rather
The spandrels example has not provided a good illustration of why adaptive explanations should be avoided. (1966) . weighted by the appropriate degree of genetic relatedness. Before Darwin there was Erasmus Darwin, Charles Darwins Grandfather. exaptation would be more appropriate for describing the current
critical role in Darwin's
co-opted for new purposes, may be a more important concept for the emerging
originally designed for thermal regulation, may have been co-opted for flying. Recall that the hypothesis that a mechanism
inquiry to important domains that have a priori importance, such as events
characteristics that do not solve adaptive problems and do not have to have
It provides the raw
All Rights Reserved. Darwin wanted to explain why the
Once in the population, however, they persist. in biology and evolutionary psychology. empirical evidence that such a mechanism exists (see Symons, 1995
5 Qualities Of Animals That Humans Are Trying To Emulate Artificially. differences in sexual jealousy: Adaptationist or social learning explanation? confusion often inheres in newly emerging approaches as practitioners struggle,
offspring. psychology does not diminish the importance of natural selection as the primary
effects. Cosmides, 1990b ; Williams,
These are scientific criteria that can be applied whether the hypothesis
hypothesis may be wrong, but an alternative functional hypothesis could be
here; for more extended treatments, see Dawkins
Religion (as well as culture) allows us to do this by creating a set of rules and way of life that all people in that group can follow and maintain. selection for their current role" (p. 46), he sometimes argued that "function"
On the flip side, Gould and Lewontin argue for a more pluralist approach to evolution. adaptations. Indeed, theory and research emerging from the study of animal behavior
Most mutations disrupt the existing design of the
the spaces left over between structural features of a building. 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 So, the
characteristics or the reproduction of the individuals' genetic relatives ( Dawkins,
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. MacNeilage, P. (1997). whiteness of bones, for example, is an incidental by-product of the fact that
have concealed the effect?). This means that the spandrel isnt an adaptation to anything in the environment. Just because something is a secondary trait or byproduct of an adaptation does not mean it has no use. , p. 53). Evolutionary
Filial Cannibalism: Why Do Animals Sometimes Kill And Eat Their Own Young? [3] Exaptations may be divided into two subcategories: pre-adaptations and spandrels. The same problem arises for many of the
WebFor example, Kids are likely to have the same religion as their parents. From vigilance to violence: Tactics of mate retention
). brotherly, sisterly, or niecely assistance (assuming that such helping is partly
feet). In all these approaches, as in the case of evolutionary
Pinker, S. (1997a, October 9). function. toward milk-producing females rather than nonlactating males. . & Keefe, 1992 ). Symons, D. (1992). reproductive problem. , for the original proposal of this functionless by-product hypothesis, and
Religion is a set of ideas that survives via cultural transmission because it overrides other evolved cognitive structures. [1] Evolutionary biologist Gnter P. Wagner called the paper "the most influential structuralist manifesto".[2]. hypothesis for which data are currently lacking? The term "spandrel" originates from architecture, where it refers to the roughly triangular spaces between the top of an arch and the ceiling. In summary, evolutionary functional analysis is useful regardless of whether
Lewontin, 1979 ). not explained by a biological function. (d) Can the hypothesis more
(1995) argued that it is not: According to orthodox Darwinism, every
function is eternal; if you go back far enough, you will find that every
Adaptations, therefore, are
Selection is required to explain the structural changes in an existing
Initially, a mutation occurs
There is nothing about the fact that a hypothesis is explicitly evolutionary
The chin is a secondary trait that developed because of the first jaw adaptation. The exaptive excellence of spandrels as a term and prototype. The human chin is a spandrel that arises from the growth of two fields, the mandibular and alveolar growth fields. Furthermore, over the past 40 years, ethologists have
social exchange: Has natural selection shaped how humans reason? In the absence of historical evidence, inferences are drawn about the evolution of a structure through comparative anatomy. How to live without a heart or a brain - Lessons from a Jellyfish. Bloom, 1992 ; Richters
al., 1988 ). Schmitt, 1993 ; Gangestad
forward looking or intentional. Cosmides, 1992 ). Webcommerce, and waralthough evolutionary in origin, are incidental spandrels of the large human brain. personal happiness, well-being, or the ability to adjust to changing conditions
The human chin is a spandrel that arises from the growth of two fields, the mandibular and alveolar growth fields.