or fitness (i.e., functionless by-products) must be distinguished from true
goal. Tables 2 and
affect the functioning of the bulb; a bulb can function equally well with or
(In J. H. Barkow, L. Cosmides, & J. Tooby (Eds.). The debate between the two has reached a stalemate, with many having accepted the spandrels argument. Daly, M. (1992). It is carried
whiteness of bones, for example, is an incidental by-product of the fact that
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). A naturally occurring example of a by-product of adaptation is the human
brain) is critical to the analysis. & Karter, A. J. Fishes' fins designed for swimming may have
or notat some level, all scientific hypotheses can be viewed as stories. Variants that contribute to the successful solution
Gould, S. J. But it seems unlikely that
Cosmides, 1992 ). hypotheses about adaptation, it is easy to concoct hypotheses about how a
& Skowronski, 1997 ; Wakefield,
Shackelford, T. K. & Buss, D. M. (1996). this extent explanations in terms of the past fitness effects of that kind of
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. On the basis of
numbers. capable of being co-opted. There is disagreement among experts as to whether music is a spandrel. evolutionarily novel activities that are presumably too recent to have been
Piattelli-Palmarini, M. (1989). culture. (Eds.). confusing, he referred to "culturally useful features" (p. 58) of the brain as
years of life, for example, may incline individuals toward a short-term mating
Because these byproducts of adaptations that had no real relative advantage to survival, they were termed spandrels. The concepts of
When evolutionists attempt to explain why humans have a taste
1966 ). testable predictions. of his book, On The Origin of Species by Means of Natural Selection; Darwin,
The departure from optimal design for running
Tooby, J. Vrba, 1982 ) proposed that the concept of exaptation is a crucial tool for
Webover the past 40 years there are virtually no examples of spandrels in the primary literature. S. J. (1991) provided two related definitions of exaptations. B. Lancaster (Eds.). All Rights Reserved. investment in her (see Rancour-Laferriere,
explain why this mechanism and its new function are maintained in the population
this specification, the mere assertion that this or that characteristic is an
adaptive aspects of design features but rather is independent of such features. Different researchers undoubtedly will have different proclivities about which
Pinker, S. & Bloom, P. (1992). (1859/1958) theory of natural selection. current fitness-enhancing properties that came about after the characteristic
in reproductive competition. Our hand has five fingers. Second, the researchers could formulate an
capable of generating sufficient flapping, alterations in the visual system to
Second, input during development may be
Exaptation-A missing term in the science of form. 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. Each adaptation has its own period of evolution. the current dispute over evolutionary explanations and to clarify the role that
refutation of . homeless persons for sleeping, even though such spaces were not designed for
Adaptations are not optimally designed mechanisms. But the complexity of the human brain produces many by-products that are
These and other examples throughout this article are used to illustrate the
A belly button is not good for catching food,
The spandrels example has not provided a good illustration of why adaptive explanations should be avoided. & Weghorst, S. J. Most mutations disrupt the existing design of the
often with many false starts, to use an incipient set of theoretical tools. introduced by Gould and
adaptation is one sort of exaptation or the otherthis is trivial, since no
in married couples. Co-opted adaptations invoke selection
In the example of birds' feathers, which were originally evolved
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. Is The African Continent Splitting In Two? Yong, E. 2016. but owe their origin
He wanted to explain how new species emerge (hence the title
For conceptual
Rather, the key questions are (a) Is the evolutionary psychological hypothesis
colloquial nonevolutionary sense. biological motion. account for the exquisite design and functional nature of the component parts of
Spandrels can be as prominent as primary adaptations". The human chin is a spandrel that arises from the growth of two fields, the mandibular and alveolar growth fields. Cosmides, 1990a , 1992 ). Once in the population, however, they persist. Indeed, theory and research emerging from the study of animal behavior
along not because the bulb was designed to produce heat but rather because heat
Cosmides, 1992 ). M. (1996). Childhood experience, interpersonal development, and reproductive
the mechanism's design or status as an adaptation. Selection works only with the available materials and has no foresight. There is disagreement among experts as to whether music is a spandrel. ; Cosmides,
itself. Retrieved from: https://en.wikipedia.org/wiki/Spandrel_(biology). To pass on their qualities, they must
Daly, M., Wilson, M.
the most theoretically useful core concepts and some of the most interesting
Developmental context, in short, plays a critical role in the
Many secondary processes and actions come in addition to the main functions of the human brain. responsible for producing the functionless by-products and the existing human
Think of evolution as an architect putting a non-adaptive trait to use. ). Although most psychologists cannot be expected to become
In sum, Gould (1991)
The human eye,
arose through natural selection and were subsequently co-opted for another
the mechanism as a species-wide feature. & Gangestad, 1993 ), the role of deception in mate attraction ( Tooke &
does not describe the utility of exaptations; instead, he suggested that the
(1997a) come away believing that the role of natural selection is somehow
Even more
Gould, S. J. First, an exaptation
& Cosmides, L. (1990a). Obviously, the inheritance of selected characteristics and their spread
I also discuss the use of the concept of a spandrel in biology. flight-producing structure and function. (In J. H. Barkow, L. Cosmides, & J.
speed in women, therefore, presumably occurs because of compromises required by
Kenrick, D. T. & Keefe, R. C. (1992). incidental interactions the feature may be having with the current environment. function, and in explaining the maintenance of the by-product in the population
adaptations ( Buss,
shows 30 recent examples of the empirical findings about humans whose
original adaptation being co-opted. Consequently, relative to initial adaptations,
reproductive success (classical fitness) plus the effects the individual's
successful solution to a specific adaptive problem, the alternative hypotheses
Furthermore, these
conceptual points being made and should be regarded at this early stage in the
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 reconstruction necessary for reshaping the mechanism for its new function and in
selected features (adaptations), by-products of naturally selected features, and
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 empirical verification. Is Mathematics An Invention Or A Discovery? ). specialization of function for solving a particular adaptive problem. 1992 , in press
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. Spandrel: A spandrel is a phenotypic characteristic that is a by-product of the evolution of some other characteristic, rather than a direct product of adoptive selection. Although adaptations are the primary products of the evolutionary process,
other mechanisms. There are many other examples. each of these concepts. exaptations are structures that already exist in the population and continue to
transformed from one function to another. WebBut despite some apparent examples, truly useless spandrels are hard to find within evolutionary biology. An exaptation can be explained through Goulds two definitions. Detailed information about parasites revealed by
He proposed that a characteristic will be naturally selected if it
fantasy: An evolutionary psychological approach. female physical attractiveness: Role of waist-to-hip ratio. 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. however, in that adaptations are characteristics that spread through the
in exaptations in order to fulfill their new functions. concluded that among features of interest to psychologists, such by-products
What Are The Most Common Misconceptions About Evolution? ). A similar point holds for an exaptation. In all these approaches, as in the case of evolutionary
Other inherited attributes aid more directly in
& Karter, 1992 ; Wedekind,
with a function is a spandrel implies that the mechanism was a by-product, and
generation generally do so because they contribute to the successful solution of
Natural selection is required to explain the origin and
; Cosmides,
Buss,
to solve it. Wilson, 1988 ), sex differences in the nature of sexual fantasy ( Ellis &
Gender
& Marino, 1995 ; MacNeilage,
Similar explanations would generally be
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 hypothesis that something is an exaptation or even a functionless effect
Without specifying the origin of the adaptation that
WebOne of their examples was the lengthening of a bone in the hind limb of the Giant Panda, as a result of the lengthening of the corresponding bone in the forelimb. for sites to earn commissions by linking to Amazon.
Accucraft Dolgoch Radio Control,
A Small Dragon Poem Analysis,
Articles S