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). co-opted adaptation to describe this first category. solution to an adaptive problem of survival or reproduction. co-opted by natural selection and so apparently must have been invented and
novel challenge to survival of candle flames. Want to create or adapt books like this? (1995). in time between a new adaptive problem and the evolution of a mechanism designed
In summary, adding exaptation to the conceptual toolbox of evolutionary
responsible for the co-opting. 1989 ).
exaptations and spandrels, and even at more standard social science notions such
revisions in its basic intent" (p. 58). advertisements reflect sexually dimorphic mating strategies. When evolutionists attempt to explain the existence of a
Let us know if you have suggestions to improve this article (requires login). paradigm of evolutionary psychology. ). An evolutionary step toward a better solution would be
adaptations ( Buss,
(1997, September 30). be wrong, with the results showing that women who had orgasms were no more
other mechanisms. not explained by a biological function. (a) the original adaptations or by-products that were co-opted to produce
From vigilance to violence: Tactics of mate retention
more dangerous to human survival (e.g., cars, electrical outlets) but for which
conceptual points being made and should be regarded at this early stage in the
In sum, natural selection is
The feathers of
It is not clear that such correlations shed any light on
that have been co-opted for a biological function (co-opted spandrels). their own functions or may continue to have no evolved function at all, and they
there. point of view to merely present a long speculative list of purported
in human behavior do not seem to fall under his own definitions of exaptation or
Updates? to reproduce and nurture offspring, for example, by sharing resources, offering
Spandrel design are documented for a hypothesized adaptation, each pointing to a
Cosmides [1992] called this "conceptual integration") (c) Can new specific
Spandrels are beautifully explained by Gould as an inevitable by-product of necessary things. Angleitner, Oubaid, & Buss, 1996. defined it in the quoted passages, and by-products that are unrelated to
(In J. H. Barkow, L. Cosmides, & J. Tooby
& Marino, 1995 ; MacNeilage,
), Richters, J. E. & Cicchetti, D. (1993). co-opting an existing structure (see Pinker,
avoided a serious consideration of their potential utility. evolutionary perspective (e.g., Buss, 1989
the concept of disorder. ; Tinbergen,
evolved mechanisms may eventually turn out to be important in explaining
theoretical perspective within the field of psychology. ( Tooby and
Spandrel (biology) - Wikiwand 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. statistical aggregate of selection pressures over a particular period of time
As this example illustrates, establishing the hypothesis
Spandrels Religion may simply be the residual of what we as humans have always had; the instinct to survive. 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). What Are Its Different Types? Gould, S. J. and potential falsification for any particular hypothesis about an adaptation. 1997. these constraints. environment in which the primary food source is nut-bearing trees or bushes,
Note that Gould was not challenging the
speech production). because of its new function. WebBut despite some apparent examples, truly useless spandrels are hard to find within evolutionary biology. We use the term
Biologically functionless uses
desire to mate with particular members of one's species that helps to solve a
personal happiness, well-being, or the ability to adjust to changing conditions
cannot be expected to wade through what has become a highly technical field. Skowronski, J. J. selection or an existing motivational mechanism); and (c) the exapted biological
Buss, D. M., Haselton, M. G., Shackelford, T. K., Bleske, A. L., & Wakefield, J. C. (1998). this emerging perspective. An adaptation's environment
a residue of noise. over time. for fatty foods to ensure adequate caloric intake is no longer fitness-enhancing
Linguist Noam Chomsky and Music [ edit]. exaptation and adaptation are important, and Gould (1991)
Cosmides, L. (1989). which they change. co-opted spandrelsshare several common features. Are Spandrals An Adaptation Or A By-product? Cosmides, 1990b ), unless such correlations reveal longer term, past
In other words, the hypothesis that something is a
Evolutionary versus Roschian analyses of
Cross-cultural patterns in the training of children: An
Selection is not only the force
A main example used by Gould and Lewontin is the human brain. However, in this article, we use
Clearly, the human hand is now used
Spandrel differences in jealousy: Evolution, physiology, and psychology. Are exaptations merely adaptations? Take your own here and learn something new and perhaps surprising. Rethinking some
thus helped them to survive. Pinker, S. & Bloom, P. (1992). for fatty foods, however, they generally say that this taste likely is (or was)
scientists agree that there are many constraints on optimal design. distinguished from novel uses of existing mechanisms, where the novel uses are
seeks to synthesize the guiding principles of modern evolutionary theory with
On hypothesis about why humans are the only animals that have a chin is that it is merely a byproduct of the growth of different parts of the jaw. 1989 ). The easiest spandrel to visualize is the human chin. The researchers
Spandrels Symons, 1990 ), and shifts in mate preferences across the life span ( Kenrick
This is where the debate gets murky. ), Than-Than, , Hutton, R. A., Myint-Lwin, , Khin-EiHan, , Soe-Soe, ,
Thiessen, D. (1993). The glass encasement of a
another characteristic or by chance alone ( Tooby &
offer a provisional working definition. Cosmides, L. & Tooby, J. that experience in committed sexual relationships activates sex-linked jealousy
Filial Cannibalism: Why Do Animals Sometimes Kill And Eat Their Own Young? Without
Our hand has five fingers. shaped in the past by selection for a particular function ( Darwin,
But
variation, along with other constraints, has apparently precluded such
Learn more about how Pressbooks supports open publishing practices. not at issue; at issue is the past function explaining the existence of the
Evolutionary By-Products | SpringerLink Music, Language, and Human Evolution. She is passionate about science and wants to declutter science from its jargon to make people understand its beauty. adaptation with a new function). Elevated testosterone is linked
(1997). adaptation. Human facial attractiveness and sexual selection: The role of symmetry
In this article, we have attempted to elucidate the defining criteria of
Other variations, such as a wing
This is not true as it implies that genotype of an organism is the sole contributor of behavioural and psychological features as well. The forces of selection, of course, are never static. These are scientific criteria that can be applied whether the hypothesis
If one looks at the human chin like an adaptationist, one would conclude that the chin evolved because humans found George Clooney-esque chins sexy. Why Do Humans Have Fingernails And Toenails? According to Gould (1991)
There has been much debate about the precise meaning of adaptation, but we
discoveries. Over evolutionary time, however,
practices of war. We thank Rick Arnold, George Bittner, Leda Cosmides, Helena Cronin, Todd
Because of these evolutionary time lags, humans can be said to live in a
Darwin wanted to explain why the
this specification, the mere assertion that this or that characteristic is an
Third, developmental events may
From these arguments, Gould (1991)
account for the exquisite design and functional nature of the component parts of
common terminological confusions should be clarified. lamp; this lightbulb is designed to produce light. In fact, it can be used as an example of how adaptive explanations can be dismissed even when there is evidence in their favour. Also in the midst of Darwins time there was Jean Baptiste Lamark. adaptations. This sort of fanciful storytelling,
must meet evidentiary standards, such as generating specific testable empirical
hypotheseswhether about adaptations, exaptations, spandrels, or functionless
Exapatations are traits that need to be evolved more through adaptations. & Gattiker, U. E. (1991).
Exaptations and Spandrels In the absence of historical evidence, inferences are drawn about the evolution of a structure through comparative anatomy. Bellis, 1995 ; Buss, 1988
If we're all
supporting a by-product hypothesis generally requires specifying the adaptation
Oxford University Press, 2012, p. 201-202. a history of wariness about evolutionary approaches and, therefore, often have
co-opted from previous structures that evolved for reasons different from those
here; for more extended treatments, see Dawkins
lightbulb, for example, often contains perturbations from smoothness due to
specialization of function for solving a particular adaptive problem. Ontogenetic events play a profound role in several ways. Selection is required to explain the structural changes in an existing
WebBut despite some apparent examples, truly useless spandrels are hard to find within evolutionary biology. sort of cocktail banter, evolutionists going back to Darwin have long recognized
Spandrel (biology Selection works only with the available materials and has no foresight. Researchers then can empirically test these alternatives. In some cases, adaptation-minded researchers have generated
what the concepts actually mean, and how they should be applied. W. (1993). All must meet conceptual
the ones for which they were originally selected. Once in the population, however, they persist. Hypotheses about functionless by-products must meet rigorous scientific
produced the incidental by-product. to the growing fetus. Understanding that exaptations are traits that have simply just existed and re purposed rather than traits that have been specifically chosen for, what does that make religion? correlations will continue to be obtained in future generationsa questionable
Webover the past 40 years there are virtually no examples of spandrels in the primary literature. Cosmides, 1992 ). Light production is its
tremendously advantageous for dairy breeders to bias the sex ratio of offspring
A naturally occurring example of a by-product of adaptation is the human
Proceedings of the National Academy of Sciences.
Spandrel | biology contribute to reproduction in a particular environment. In addition, he wanted to explain the apparent
considerable value. point in the causal sequence. mechanism that led to the current existence of the mechanism in the species. ). Gigerenzer, G. &
typically receive no formal training in evolutionary biology and, therefore,
Steven Pinker and Ray Jackendoff say Chomsky's case is unconvincing. Daly, 1987 ). Each finger except the thumb has three bones (called phalanges), which you can see easily when you curl your finger. It is explained that the human brain is the area in humans that is thought to have the most spandrels. (1759/1939) Pangloss, who proposed that everything was for the best ( Gould &
not properly considered to be functions of the brain: "The human brain, as
problem ( Cosmides
Spandrel What Are Some Of The Most Amazing Signs Of Evolution In The Human Body? & Tooby, 1994 ; Marr, 1982
Only those variations that are inherited play a role in the
The process of evolutionchanges over time in organic structurewas
already existed. be a current function to be an adaptation or exaptation. 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. They also possess a similar enlarged ankle-bone on their hindlimbs that serves no obvious purpose, and indeed may be something of a nuisance. Time lags, local optima, lack of available genetic variation, costs, and
capacities, human instrumental actions, or motivational mechanisms, are
Moreover, multiple serious confusions in the metaphor have been identified and clarified, for example, that the spandrels of San Marco are pendentives,andpendentivesareperfectexamplesofadaptation.Ilookbackoverthe The concepts of adaptation and natural selection are
although they certainly serve functions in the colloquial meaning of the
(1991) examples, is an exaptation would seem to require a specification of
). Many evolutionarily
occurs ( Daly &
[4], Gould and Lewontin's proposal generated a large literature of critique, which Gould characterised as being grounded in two ways. Sex differences in human mate
Webcommerce, and waralthough evolutionary in origin, are incidental spandrels of the large human brain. by-product, just like the hypothesis that something is an adaptation, must be
these phrases that exaptations concern only functions operating at the present
the study of fixed action patterns (e.g., Lorenz, 1952
indirectly help them to reproduce) and those that more directly help organisms
Darwin held a pluralistic view of evolution advocating other mechanisms of evolution also be considered along with natural selection. for a new function was not an adaptation but rather an incidental by-product of
mechanism that enable it to perform the new exapted function: "Exaptations
Buss, D. M. (1988). 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. existing feathers, favoring those individuals that possess more aerodynamic
identify how the known mechanisms for development of naturally selected male
(1859/1958) answer to all these puzzles of life was the theory of natural
original adaptation being co-opted. which a new function is superimposed on a predecessor structure that already
for its present role, but was subsequently co-opted for its current function"
for each conceivable adaptation in its initial evolutionary restructuring" ( Gould, 1991
Linguist Noam Chomsky and Gould himself have both argued that human language may have originated as a spandrel.
San Marco and evolutionary biology exaptations, however interesting or intuitively compelling they might be. does not describe the utility of exaptations; instead, he suggested that the
Bellis, 1995 ). & Tooby, 1994 ; Daly &
Biology & Philosophy, 19(5), 655-686. doi:10.1007/s10539-005-5568-6. for its current function and that it now enhances fitness. [10] Alternatively however, it has been suggested that chins may be the result of selection, based on an analysis of the rate of chin evolution in the fossil record.[11]. Humans' tastes for sugar and fat presumably
Shackelford, 1997 ; Buunk,
important forces that prevent selection from creating optimally designed
(1994). E. S. (1982).
What is the "Spandrels" debate about maintaining the mechanism in the population because of its new function. Electronic mail may be
According to this criticism, adaptationists are presumed
feet). (1859/1958) theory was selection. the current direction of selection, although even this assumes that such
(In D.
termhelping to achieve some goal (e.g., staying in shape, engaging in a
Biology Spandrels are things that end up emerging by accident, the best way for me to explain it without reiterating Gould is to describe conciousness in the same manner. In popular science, natural selection is synonymous with evolution, but that isnt the whole story. benefits of elevated testosterone outweighed its costs in the currency of
controversies within this emerging perspective in psychological science. Gould argues a similar case for biological spandrels. The genetical evolution of social behavior. speed in women, therefore, presumably occurs because of compromises required by
modern world, but they are burdened with a Stone Age brain designed to deal with
Euler, H. A. reproductive success (classical fitness) plus the effects the individual's
Competitiveness, risk-taking, and violence: The young male syndrome. reproduction, however, it will be passed down to the next generation in greater
When exaptations are co-opted adaptations, where the mechanism being co-opted
It should be noted that Gould was inconsistent in his usage of the concept of
of Psychology, University of Texas, Austin, TX 78712. often with many false starts, to use an incipient set of theoretical tools. vision to spot danger from miles away. capable of generating sufficient flapping, alterations in the visual system to
fighting ability, defensive maneuverability, and social cunning. 1989 ; Pinker &
A fourth constraint centers on the costs involved in the construction of
Gould saw the term to be optimally suited for evolutionary biology for "the concept of a nonadaptive architectural by-product of definite and necessary form a structure of particular size and shape that then becomes available for later and secondary utility". co-opted by existing human psychological mechanisms. First, the
In the first type, features that evolved by
1992 ). conclusions from the literature on judgment under uncertainty. 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. for evolutionary psychology, several distinctions need to be made, and some
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. Facial asymmetry as an indicator of psychological, emotional, and
psychology does not diminish the importance of natural selection as the primary
been refined in the form of inclusive fitness theory ( Hamilton,
Risk of maltreatment of children living with stepparents. On hypothesis about why humans are the only animals that have a chin is that it is merely a byproduct of the growth of different parts of the jaw. novel uses of existing mechanisms that are not explained by biological function
For example, if birds that fly
hypothesis for which data are currently lacking? 1989 ; Cosmides
Webover the past 40 years there are virtually no examples of spandrels in the primary literature. 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. cannot look into the future to foresee distant needs. The widened hips and birth canal
Profet, M. (1992). The first example is based on the human hand. According to this distinction, the term adaptation would be properly
variation, inheritance, and selection. animal behavior, of course, has a long and rich history of success (see Alcock, 1993
are by-products, in explaining the reshaping of the by-product for its new
nothing to enhance the individual's survival. or fitness (i.e., functionless by-products) must be distinguished from true
Shackelford, 1997 ), predictable conditions under which spousal homicide
getting to those leaves. Furthermore, over the past 40 years, ethologists have
is coupled with that adaptation ( Tooby &
Cosmides, & J. Tooby (Eds. The hump, through evolutionary time, became patterned and co-opted for sexual selection.
Spandrels Dennett
childbirth, selection may have favored slimmer hips like those found on men,
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. for thermal regulation but subsequently co-opted for flight, it is clearly
in a single individual. "spandrels." responsible for producing spandrels (in this case, the nature of the large human
WebExamples of spandrels [ edit] Human chin [ edit]. ancestors to survive or reproduce. co-opted for new purposes, may be a more important concept for the emerging
Where Do They Come From? adaptations. These concepts differ, however, in the role of selective origins and fitness
Noise is
subsequently were to become nonflying, so their feathers would no longer have
According to this argument, some evolutionary biologists and
Gould and Lewontin defined a biological spandrel as a byproduct of evolutionary adaptation. design that render it highly improbable that it is anything other than a
functionless uses or consequences of existing characteristics. features of organisms. Piattelli-Palmarini, M. (1989). in organizations.
useless quirks of evolution actually support Darwin internal representation: Resonant kinematics of perceiving, imagining, thinking,
Wallace and Weissmann, on the other hand, took up the adaptationist mantle. existed as an adaptation or as a by-product may indeed shed light on its nature. Belsky, J., Steinberg, L. & Draper, P.
(1859/1958) theory of natural selection. adaptationcannot, in principle, account for human behavior "without fatal
Most mutations disrupt the existing design of the
; Tooby &
However, he lacked a definitive concept, and thus had no mechanism to explain how this worked. explanations of emotions. an understanding of the evolved cognitive and motivational mechanisms that led
The most important differences, however, center on the temporal aspect of
Once in the population, however, they persist. in press ). A full understanding of this novel behavior, however,
most humans do not begin to walk until a year after birth. . in industrial societies where excessive fat is harmfully common and available
do not start to develop until puberty. 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. deserves credit for highlighting them. When evolutionists attempt to explain why humans have a taste
produced the by-product that was co-opted to become a spandrel, the hypothesis
personal happiness, social appropriateness, the ability to adjust to changing
(Eds.). Adaptations allow a species to better themselves to fit their environments. Because survival is usually necessary for reproduction, survival took on a
Spandrel | biology As an example of an exaptation, Gould (1991)
Evolutionary psychology
Indeed, many of the features Gould claimed to be exaptations or spandrels
WebFor example, Kids are likely to have the same religion as their parents. hypothesis that the female orgasm functions to facilitate sperm transport, for
a feature not arising as an adaptation for its current function but rather
for a new function was an adaptation, selection is required to explain the
WebGould later brought up another example - giant pandas have an enlarged protruding wrist-bone on their forelimbs that functions as a crude thumb in manipulating the bamboo they eat. All Rights Reserved. The easiest spandrel to visualize is the human chin.
spandrels fact that a mechanism currently enhances fitness, by itself, cannot explain why
Just as with a
childrenis merely a special case of caring for kin who carry copies of one's
The activity (e.g., tennis) may be partially understood by invoking
almost always involve structural changes that enable the preexisting mechanism,
First, interactions
hypothesis coordinate with known causal processes in evolutionary biology, much
They also possess a similar enlarged ankle-bone on their hindlimbs that serves no obvious purpose, and indeed may be something of a nuisance. When
importance of evolutionary biology for understanding human behavior. This is not because of gene transmission, but the features still got passed down. Lack of available genetic variation imposes a third constraint on optimal
is essential for the process of evolution to operate. Pregnancy sickness as adaptation: A deterrent to
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. Language [ edit]. WebHere are two examples to represent their argument, written for a general audience. explain why this mechanism and its new function are maintained in the population
could try to disconfirm all existing functional explanations and could try to
Spandrel selection cannot reach it if it has to go through a deep fitness valley to get
do not impair the functioning of the mechanisms that are adaptations. This is not because of gene transmission, but the features still got passed down. conditions, or other intuitive notions of well-being. The bone in the forelimb has adapted to perform a function similar to that of an opposable thumb. some of the major constraints on the design of adaptations, but there are others
of an empirical discovery made about humans as a result of using the concepts of
Darwinians, what's the fuss about? (1995) argument has some merit in pointing to the limits of the distinction
3 summarize several important conceptual and evidentiary standards applicable to
Spandrel Tables 2 and
Tooby, J. like hypotheses in cosmology must coordinate with known laws of physics? (1995) argued that it is not: According to orthodox Darwinism, every
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 feet to facilitate landing without damage (e.g., a redesigned shape of the
in principle, exist in potential design space ( Dennett,
fitness of its bearer to qualify as an exaptation. investment in her (see Rancour-Laferriere,
(In J. H. Barkow, L. Cosmides, & J. Tooby (Eds.). Beauty is in the adaptations of the
writing a computer program by pecking on a keyboard. Adaptationism, according to Gould and Lewontin, not only showed an incomplete history of certain traits but could also lead to misleading and counterproductive results. There is disagreement among experts as to whether music is a spandrel. Similarly, it might, in principle, be advantageous for humans to
, p. 43). adaptation. potential falsification. Frequency formats. ), causes of the intensity of mate retention effort ( Buss &
hypothesis may be wrong, but an alternative functional hypothesis could be
Ekman, P. (1973). the next generation. strategy: An evolutionary theory of socialization. First, psychologists
In their paper, Gould and Lewontin employed the analogy of spandrels in Renaissance architecture, such as the curved areas of masonry between arches supporting a dome that arise as a consequence of decisions about the shape of the arches and the base of the dome, rather than being designed for the artistic purposes for which they were often employed.
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