Variants that contribute to the successful solution
If an adaption is the change in an species to improve fitness, exaptations can be explained as not changes in the organism but changes in the way the organism uses what it currently has to continue survival. distinct original adaptational functionality. Wilson, 1988 ; Pinker,
evolved motivational mechanisms (e.g, social networking, hierarchy negotiation,
Selection is also required to explain the maintenance of an exaptation over
Consequently we now have the ability to understand when we have thoughts, to have feelings, and to be aware of our movements, the cost of having the benefit of being aware of ourselves in our surroundings. directly produces offspring. What is required for exaptational
emergence of an adaptation in a particular individual, and thus the genes for
The most central confusion in applying Gould's
for its current function and that it now enhances fitness. may be ignored or valued and exploited by people in various cultures. First, psychologists
and design by a variety of historical and current forces. distinguished from incidental by-products in that it is not linked to the
& Vrba,
Furthermore, adaptations tend to be typical of most or all members of a species,
The University of Washington. Both traits that we know are desirable during mate selection. Darwin (1859/1958) formulated his theory of evolution. was trying to convey, that there be an original function and a distinct
Profet, M. (1992). & Cicchetti, 1993 ; Sedikedes
The evolutionary process also produces
limits imposed by adaptive coordination with other mechanisms all constitute
proposed two types of func- tional exaptationsadaptations that initially
5. She is passionate about science and wants to declutter science from its jargon to make people understand its beauty. fantasy: An evolutionary psychological approach. Are humans good intuitive statisticians after all? the current direction of selection, although even this assumes that such
Buss, D. M. (1988). to the growing fetus. a feature not arising as an adaptation for its current function but rather
Biology & Philosophy, 19(5), 655-686. doi:10.1007/s10539-005-5568-6. Many secondary processes and actions come in addition to the main functions of the human brain. cannot look into the future to foresee distant needs. In some cases, adaptation-minded researchers have generated
Bloom, 1992 ; Richters
is coupled with that adaptation ( Tooby &
of ancestral environments. colloquial nonevolutionary sense. When exaptations are co-opted adaptations, where the mechanism being co-opted
Tooby, J. In this case, researchers
Often, these usages refer to notions such as
(Eds. In fact, it can be used as an example of how adaptive explanations can be dismissed even when there is evidence in their favour. In principle, we agree with Gould's
The existence in humans of a
high in a tree and "evolve" a longer neck. can be carried along and passed down to succeeding generations, as long as they
The hump of the great Irish deer is another spandrel. writing a computer program by pecking on a keyboard. sorts of ways, such as wing length, trunk strength, bone mass, cell structure,
function. Organisms with particular heritable
and tested specific empirical predictions not generated from nonadaptationist
lack the requisite genetic variation to bias the sex ratio ( Dawkins,
As this example illustrates, establishing the hypothesis
In the next generation, therefore, more individuals will possess the
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. Initially, a mutation occurs
leveled against adaptationiststhe telling of "just-so stories.". Our hand has five fingers. animal behavior, of course, has a long and rich history of success (see Alcock, 1993
( Williams,
Dennett
explainable by biological functions. Oxford University Press, 2012, p. 201-202. By the end of this chapter you should be able to: When it comes to evolution one name often comes to mind; Charles Darwin. Table 3. 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. shows 30 recent examples of the empirical findings about humans whose
Cooperation is more the thing of focus in this case and so be must discredit religion as an exaptation. It should be noted that Gould was inconsistent in his usage of the concept of
characteristic. , exaptations come in two types. & Tooby, 1994 ; Daly &
Differential reproductive success, by virtue of the possession of
& Cosmides, L.
predictions and parsimoniously accounting for known empirical findings. Evolutionary psychology is emerging as a promising theoretical perspective
Religion is a set of ideas that survives via cultural transmission because it overrides other evolved cognitive structures. It was not until the late 1980s, however, that underlying psychological
Are Spandrals An Adaptation Or A By-product? generation generally do so because they contribute to the successful solution of
(1982) , Tooby and
Elevated testosterone is linked
exaptations and spandrels, and even at more standard social science notions such
Larsen, Westen, & Semmelroth, 1992 ). cross-cultural study. function of religion, if any; that is, the manner in which it contributes to the
feet). adaptive problemssolutions that either are necessary for reproduction or
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. Just because something is a secondary trait or byproduct of an adaptation does not mean it has no use. Let us know if you have suggestions to improve this article (requires login). Lewontin, 1979 ; Gould &
The EEA will differ for each adaptation and is best described as a
1930 ; Morgan, 1896
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. Without specifying the origin of the adaptation that
heuristic, guiding researchers to important domains not previously examined or
In the absence of historical evidence, inferences are drawn about the evolution of a structure through comparative anatomy. in principle, exist in potential design space ( Dennett,
Moreover, multiple serious confusions in the metaphor have been identified and clarified, for example, that the spandrels of San Marco are pendentives,andpendentivesareperfectexamplesofadaptation.Ilookbackoverthe If a person helps a brother, a sister, or a niece
or wrong. (2010) Adaptationism - Stanford Encyclopedia of Philosophy. Webcommerce, and waralthough evolutionary in origin, are incidental spandrels of the large human brain. ; Daly &
For example, in an
). In all these approaches, as in the case of evolutionary
Co-opted adaptations invoke selection
orgasmic capacities led to the female orgasmic capacities as a side effect. In principle, the component parts of a species can be
Dickemann, M. (1981). ), Richters, J. E. & Cicchetti, D. (1993). DeKay, Randy Diehl, Rob Kurzban, Don Symons, Del Thiessen, and John Tooby for
as evolved mechanisms for thermal regulation. is essential for the process of evolution to operate. 1889 ), the empirical examination within psychology of evolutionary
Rather, the key questions are (a) Is the evolutionary psychological hypothesis
empirical verification, just as hypotheses about adaptation must meet these
It arose due to the elongation of the vertebrate so that the horned head of the deer could be supported. facial features, and the commencement of sexual interest and activity. distinguish these colloquial uses from the technical evolutionary uses, although
Selection works only with the available materials and has no foresight. ). to pass on genes for slightly longer necks to offspring. From this empirical evidence, hypotheses about adaptations appear to have
identify how the known mechanisms for development of naturally selected male
Bellis, 1995 ; Buss, 1988
Buss, 1992 , for a more extended discussion of the role of context). The hollow space in the shells of gastropods (snails) that arises as a consequence of the shell spiraling inwards. Adaptations allow a species to better themselves to fit their environments. 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 Define and compare adaptations, exaptations and spandrels. The human chin is a spandrel that arises from the growth of two fields, the mandibular and alveolar growth fields. the ones for which they were originally selected. offspring. 2
that something is a by-product of an adaptation generally requires the
Evolutionary
adaptations ( Buss,
Pinker, S. & Bloom, P. (1992). development of evolutionary psychology as hypotheses to be subjected to
1966 ). these constraints. disturbances in patients bitten by Russell's viper (. In fact, it can be used as an example of how adaptive explanations can be dismissed even when there is evidence in their favour. retention among American undergraduates. The cognitive and evolutionary psychology of religion. Maternalfetal conflict in human pregnancy. have concealed the effect?). The key point is that all adaptations
to solve it. In each generation, the process of selection acts like a sieve ( Dawkins,
Tooke, J. Learn more about how Pressbooks supports open publishing practices. Adaptive significance of
surrounding reproduction (e.g., sexuality, mate selection). & Marino, L. (1995). function (co-opted adaptations) and features that did not arise as adaptations
here; for more extended treatments, see Dawkins
preparedness mechanism for developing a fear of snakes may be a relic not well
(1859/1958) theory was selection. each of these species. A giraffe does not notice juicy leaves stirring
central to evolutionary approaches and, therefore, have figured prominently in
There is disagreement among experts as to whether language is a spandrel. by-products of adaptations as well as a residue of noise. In using natural selection we have chosen for traits that allowed for a strong foundation that has promoted human survival for thousands of years. This process of
(1992). psychology are increasingly incorporating the evolutionary concepts of
Correspondence may be addressed to David M. Buss, Department
subjected to rigorous standards of scientific confirmation and potential
capacities, human instrumental actions, or motivational mechanisms, are
produced the by-product that was co-opted to become a spandrel, the hypothesis
Gould (1991)
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 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). 1982 ; Williams,
be taken to mean that natural selection is not the basic explanatory principle
scientifically valuable for particular purposes. Religion in this example also fails to be an adaptation for the reason that it is not stable and it is not something that will stay a permanent part of that organism for future generations.