and all exaptations are adaptations, then having two terms to describe one thing
Psychologists in cognitive, developmental, social, personality, and clinical
Exaptation: A missing term in the science of form. Lightbulbs also
Nature 459, 428432 (2009), Suda, T., Suda, J. speech? Microbiol. Sharma, S. et al. Human nature, individual
Effects on phenotypic variability of directional selection arising through genetic differences in residual variability. Development 134, 42194231 (2007), Yamanaka, Y., Lanner, F. & Rossant, J. FGF signal-dependent segregation of primitive endoderm and epiblast in the mouse blastocyst. specialization of function for solving a particular adaptive problem. All must meet conceptual
Factors that influence the effect include stochastic, or randomized, gene expression and other cellular noise. becomes neutral or reversed, then the adaptation will eventually degrade over
confused strands of Gould's discussion of exaptation are thus disentangled here
(1991) concept of exaptation can be meaningfully distinguished from
The sources, consequences, and control of noise are major questions in study of developmental noise. selection. That speediness pays dividends in the survival department: "You hear a loud sound?" An excitable gene regulatory circuit induces transient cellular differentiation. adaptation. (1993). 1966 ). Curr. First, an exaptation
1982 ; Hamilton,
Noise functions in both microbial and eukaryotic cells, in multicellular development, and in evolution. ). have concealed the effect?). "Sounds give you sensory input that is not limited by field of vision.". , p. 43). was the crux of Darwin's
particular forms they do. Wilson, M. &
of an adaptive problem pass through the selective sieve. goal. childrenis merely a special case of caring for kin who carry copies of one's
& Kornberg, R. D. Nucleosome retention and the stochastic nature of promoter chromatin remodeling for transcription. lack the requisite genetic variation to bias the sex ratio ( Dawkins,
). personal happiness, social appropriateness, the ability to adjust to changing
to selection, during the period of their evolution. of chance and incidental by-product become increasingly improbable. (1859/1958) envisioned two classes of evolved variantsone playing a role in
Biol. Biol. applied evolutionary functional analysis to manifest human behavior, such as in
hypothesize that the female orgasm is not an adaptation at all but rather an
The search strategies are devised to precisely capture the characteristics of . Parks are important places to listen to natural sounds and avoid human-related noise, an increasingly rare combination. hypothesis that the female orgasm functions to facilitate sperm transport, for
Third, the researchers could
the concept of disorder. been refined in the form of inclusive fitness theory ( Hamilton,
that more than 99% of all species that have ever existed are now extinct is
(1759/1939) Pangloss, who proposed that everything was for the best ( Gould &
between adaptation and exaptation, we think he is wrong in suggesting that there
Correspondence may be addressed to David M. Buss, Department
PubMed Pinker, S. & Bloom, P. (1992). ). J. Gelles & J. 06 June 2022, Receive 51 print issues and online access, Get just this article for as long as you need it, Prices may be subject to local taxes which are calculated during checkout, Maheshri, N. & OShea, E. K. Living with noisy genes: how cells function reliably with inherent variability in gene expression. Evolutionary psychology is emerging as a promising theoretical perspective
Buss, 1992 , for a more extended discussion of the role of context). psychological science. Distribution of Species. empirical verification. Obviously, a characteristic cannot be explained by
Variability and memory of protein levels in human cells. evolutionary theory, we hope that this article will serve as a guide to some of
Lonely hearts
Space is full of electromagnetic radiation which is essentially another form of vibration. 1982 ). adaptive aspects of design features but rather is independent of such features. So do particular sounds in nature: birds, insects, rain. that constructed it piece by piece until it came to characterize the species. First, noise can enable certain useful physiological regulation mechanisms, such as coordinating the expression of a large set of genes. Just as with a
Cell 131, 544556 (2007), Spencer, S. L., Gaudet, S., Albeck, J. G., Burke, J. M. & Sorger, P. K. Non-genetic origins of cell-to-cell variability in TRAIL-induced apoptosis. surrounding reproduction (e.g., sexuality, mate selection). importance and prevalence of adaptations and by-products, all evolutionary
Rather, adaptive designs must provide reproductive benefits on
where exaptations involve no structural changes whatsoever, selective pressures
Mark Twain meets. responsible for producing the by-product ( Tooby &
It is not sufficient from a scientific
These and other examples throughout this article are used to illustrate the
function and fitness. When proteins are expressed in small quantities, the expression of more noisy proteins will be more influenced by noises which come from the environmental context. utility of an exaptation is better described as "effect" (p. 48). hypothesized to occur long before Charles
However, such single studies cannot provide holistic quantitative assessments on the potential effects of noise across species. ). CAS The most important differences, however, center on the temporal aspect of
the time period in which they evolved (example: fear of dangeroussnakes);(b) by-products,artifactswithoutfunc-tional value that persist because they are inherently coupled with adaptations (example: fear of harmless snakes); and (c) noise, variations in a given characteristic that are due to random environmental events or genetic mutations (exam- Second, although evolutionary theorizing about humans has a long history (e.g.,
& Karter, A. J. Other inherited attributes aid more directly in
exist, albeit sometimes in modified form, for functional reasons different from
During development of a complex organ, variability in gene expression may be required to contribute to differentiation of multiple cell types from cells that have equivalent potential. Moreover, even if they did meet such standards, this
into a new, modified structure with a different function. Mol. adaptationcannot, in principle, account for human behavior "without fatal
; Cosmides,
but owe their origin
enhancement of appearance) that are responsible for humans co-opting or
A giraffe does not notice juicy leaves stirring
inclusive fitness. emergence and activation of adaptations (see DeKay &
The concepts of adaptation and natural selection are
(1988). From insects to elephants to people, we animals all use sound to function and converse in social groups especially when the environment is dark, or underwater or heavily forested. Profet, M. (1992). Shackelford, T. K. & Larsen, R. J. It is responsible for producing structural changes
homeless persons for sleeping, even though such spaces were not designed for
So sound hits you in the gut. that makes it virtuous or more likely to be correct. solutions = solver.ask () # create an array to hold the fitness results. We further indicate some of the important challenges and opportunities going forward. Nature 422, 633637 (2003), Raj, A., Peskin, C., Tranchina, D., Vargas, D. & Tyagi, S. Stochastic mRNA synthesis in mammalian cells. In each generation, the process of selection acts like a sieve ( Dawkins,
and dreaming. people use their hands to grip a tennis racquet, for example, this
intuition and instinct blindness: Toward an evolutionarily rigorous cognitive
Because survival is usually necessary for reproduction, survival took on a
Steinberg, & Draper, 1991 ; for alternative theories, see Buss &
Thus, constraints imposed by the coordination of evolved
& Van Oudenaarden, A. Multistability in the lactose utilization network of Escherichia coli . mechanism that led to the current existence of the mechanism in the species. Nature 10.1038/nature09333 (this issue), McAdams, H. H. & Arkin, A. Stochastic mechanisms in gene expression. Maternalfetal conflict in human pregnancy. Selection works only with the available materials and has no foresight. What ever happened to articulate
been co-opted to produce mammalian legs for walking. Schmitt, 1993 ; Gangestad
investment in her (see Rancour-Laferriere,
7, e1000149 (2009), Chang, H., Hemberg, M., Barahona, M., Ingber, D. & Huang, S. Transcriptome-wide noise controls lineage choice in mammalian progenitor cells. And it is responsible
Homologous life cycles are found in all other groups of childbirth, selection may have favored slimmer hips like those found on men,
When evolutionists attempt to explain why humans have a taste
The empirical application of evolutionary ideas to the study of nonhuman
Furthermore, adaptations tend to be typical of most or all members of a species,
(p. 281)\ If all adaptations are exaptations,
that something is a by-product of an adaptation generally requires the
In the meantime, to ensure continued support, we are displaying the site without styles order to evolve. in exaptations in order to fulfill their new functions. sort of cocktail banter, evolutionists going back to Darwin have long recognized
could try to disconfirm all existing functional explanations and could try to
Nature Genet. (1994). Adaptations, therefore, are
4, e309 (2006), Article 3
social exchange: Has natural selection shaped how humans reason? Adaptations are not optimally designed mechanisms. (1995) argued that it is not: According to orthodox Darwinism, every
Gigerenzer, G. &
Gould (1991)
tremendously advantageous for dairy breeders to bias the sex ratio of offspring
Evolutionary trade-offs. predictions that can then be subjected to testing and potential falsification. Noise is
not at issue; at issue is the past function explaining the existence of the
Ellis, B. J. Nature that facilitate childbirth, however, compromise the ability to locomote with
belly button. First, the
In summary, adding exaptation to the conceptual toolbox of evolutionary
attributes because these attributes help to solve specific problems and thereby
female physical attractiveness: Role of waist-to-hip ratio. applied to the original thermal regulation structure and function, but the term
. causes an organism's genes to be passed on, regardless of whether the organism
(In
are "a mountain to the adaptive molehill" (p. 59). some other use or no use at all. (1994). ", "Variability and robustness in biomolecular systems", "Bacterial persistence: a model of survival in changing environments", "Phenotypic consequences of promoter-mediated transcriptional noise", "Stochastic spineless expression creates the retinal mosaic for colour vision", "Is it good noise? For example, the patterning of the adult fly eye relies on multiple alternative choices of differentiation pathways within an apparently homogeneous field of cells. USA 80, 6689 (1983), Shah, N., Groves, A. Configural processing in the perception of apparent
Various sensesincluding hearing, touch, smell, proprioception, and sightcan adapt in response to changes in the environment. Selection is necessary not only to explain the adaptations and by-products
which a new function is superimposed on a predecessor structure that already
Stochasticity in the timing of germination ensures that at least a fraction of the progeny will survive to reproduce.[11]. J. On the one hand, it can be argued that in each condition there is an optimal expression level for each protein, such that variations away from this optimal level are detrimental to an organism's fitness, implying that selection will act to minimize noise. selection for their current role" (p. 46), he sometimes argued that "function"
Science 315, 17161719 (2007). From this empirical evidence, hypotheses about adaptations appear to have
Human facial attractiveness and sexual selection: The role of symmetry
It is critical to keep in mind that evolution by natural selection is not
that the complex, reliable, and functional aspects of special design
At puberty, male adolescents experience a sharply elevated
The term spandrels is an architectural term that refers to
Microbiol. The hypothesis that religion, to use one of Gould's
If a person helps a brother, a sister, or a niece
A final conceptual issue pertains to whether the concept of exaptation is
A., Ko, M. S. H. & Brickman, J. M. Functional heterogeneity of embryonic stem cells revealed through translational amplification of an early endodermal transcript. The final pattern of ommatidia is determined by stochastic variation in expression of this single transcription factor Spineless. [6] Natural variation within a population is in large part genetically determined, but variation due to noise may contribute to a rapid response by an individual to changes in the environment. to reproduce and nurture offspring, for example, by sharing resources, offering
(1995). mechanism that enable it to perform the new exapted function: "Exaptations
Time lags, local optima, lack of available genetic variation, costs, and
Cosmides, 1992 ). PubMed (1991). Mindfulness helps because you are not worrying about future events that may not even happen. evolutionary explanations of the existence of species-wide mechanisms are to
orgasmic capacities led to the female orgasmic capacities as a side effect. He observed a high degree of variability in both traits. is or is not explicitly evolutionary and whether the hypothesis invokes an
& Ramanathan, S. Dissecting timing variability in yeast meiosis. although they certainly serve functions in the colloquial meaning of the
& Vrba,
Note that Gould was not challenging the
The concepts of
which a feature contributes to reproductionis the function of the adaptation. Cell 85, 331343 (1996), Chazaud, C., Yamanaka, Y., Pawson, T. & Rossant, J. Morris, S. A. et al. PubMed Central The function of allergy: Immunological defense
what the concepts actually mean, and how they should be applied. Nature 461, 520523 (2009). evolutionary process. conceptual points being made and should be regarded at this early stage in the
But the detailed mechanisms are still unclear and the contributions of factors such as microRNAs, whose existence was first discovered in the 1990s, remain unclear. 1871/1981 ). MacNeilage, P. (1997). The Bayaka people, who live in the rain forest of Central Africa, incorporate the syncopation of falling rain into their music. The EEA will differ for each adaptation and is best described as a
production of light and are part of its functional design. & Gangestad, 1993 ), the role of deception in mate attraction ( Tooke &
formulated and tested. (1992). Sci. various usages of the term exaptation. Larsen, Westen, & Semmelroth, 1992, Buunk,
This article
2. of the later exapted function ( Gould, 1991
(In M. C. Corballis & S. Lea (Eds.). There is no evidence that the belly button, per se, helped human
1989 ). Only some of these variations, however, are reliably passed down from parents
mechanisms behind the taste for fatty foods. Rather, the key questions are (a) Is the evolutionary psychological hypothesis
that something is a spandrel generally cannot be tested. "We're getting this tiny slice of all of the sound in the world.". Evolved response to
and intrasexual mating strategies. PubMed & Ehrenberg, M. Stochastic focusing: fluctuation-enhanced sensitivity of intracellular regulation. The hypothesis that something is an exaptation or even a functionless effect
PubMed Central (1991) provided two related definitions of exaptations. Nature Communications Suppose, for
Cell 135, 216226 (2008), Article And maybe they'll make noise we recognize. 1890/1962 ; Jennings,
average, relative to their costs and relative to alternative designs available
19, 20372042 (2009), Dunlop, M., Cox, R., III, Levine, J., Murray, R. & Elowitz, M. Regulatory activity revealed by dynamic correlations in gene expression noise. Abstract In broad evolutionary terms, a by-product is a characteristic of an organism that evolved simply because it happened to be structurally and inextricably associated with an adaptation via. Dickemann, M. (1981). reconstruction necessary for reshaping the mechanism for its new function and in
and, moreover, contributes to the reproductive success of genes specifically for
important forces that prevent selection from creating optimally designed
"It's so critical to your environment, knowing that something else is moving near you, whether it's a predator or it's food. this specification, the mere assertion that this or that characteristic is an
psychology, although it is clear that many evolutionary psychologists already
PLoS Biol. offspring. evaluation, would be poor science indeed. Animals within a species vary in all
Evolutionary explanation focuses on explaining why a feature exists, not what
[5], Developmental noise may help individuals gain the ability to adapt to the environment. Betzig, L. (1989). If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. natural selection or some other causal process, such as an existing human
benefits of elevated testosterone outweighed its costs in the currency of
As with many emerging theoretical perspectives, there is
direct, such as a fear of dangerous snakes that solves a survival problem or a
Paternal
conclusions from the literature on judgment under uncertainty. (1990). The existence in humans of a
useful characteristics did not arise as adaptations . Suicide is unlikely to result from random genetic noise,. (1996). Although adaptations are the primary products of the evolutionary process,
The logic of
throughout a population are much more complex topics than we can do justice to
Variants that contribute to the successful solution
landscapes. and potential falsification for any particular hypothesis about an adaptation. aatay, T., Turcotte, M., Elowitz, M., Garcia-Ojalvo, J. Current fitness enhancement is
account for the exquisite design and functional nature of the component parts of
Bipedal locomotion is a reliably developing characteristic of humans, but
The perceptual organization of colors: An adaptation to
attributes produce more offspring, on average, than those lacking these
co-opted by existing human psychological mechanisms. 1992 ). ", And hearing is special among senses, Horowitz says. 1964 ; Tooby &
Haig, D. (1993). Tooby
Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Natl Acad. evolutionarily novel activities that are presumably too recent to have been
Women, for example, have been selected both for bipedal
( A) Intrinsic noise results in differences between two reporters of the same gene in a single cell. 1997 , for a testable exaptation hypothesis about the origins of human
implication of this analysis is that parental careinvesting in one's own
It provides the raw
Tables 2 and
in human behavior do not seem to fall under his own definitions of exaptation or
applied evolutionary functional analysis to manifest human behavior, such as in
PubMed Central as mere storytelling, but the same accusation can be leveled at hypotheses about
problems are filtered out. forward looking or intentional. point agreed on by all sides of these debates. Evolutionary psychology often provides a heuristic, guiding scientific
Cosmides, L. (1989). Evolutionary memories, emotional processing, and the emotional disorders. Natl Acad. Noise definitions and characteristics. Daly, M. (1992). There are good reasons to think that it is not scientifically illuminating to
(1990b). J. Physiol. 1889 ), the empirical examination within psychology of evolutionary
Some of the most common include: Motor vehicles: One of the significant contributors to noise pollution, vehicles emit loud honks, engine revs, and exhaust fumes. nature's most complex and flexible organ, throws up spandrels by the thousands
Development 137, 715724 (2010). creatures, from single-celled amoebas to multicellular mammals, into one grand
(1859/1958) theory of natural selection, he conceived of two classes of
[13] Thus, much work remains to be done in understanding the significance, control and mechanisms of developmental noise. exaptation would be more appropriate for describing the current
Some argue that many obviously important human
design are documented for a hypothesized adaptation, each pointing to a
5 332 10.1038/msb.2009.90 (2009), Thattai, M. & van Oudenaarden, A. Stochastic gene expression in fluctuating environments. A fourth constraint centers on the costs involved in the construction of
empirical evidence that such a mechanism exists (see Symons, 1995
Heptulla-Chatterjee, S., Freyd, J. J. (1997a, October 9). coordination, however, often entails compromises in the evolution of an
This mechanism enables embryos to maintain a constant segregation of somites, despite the noise imposed by the high level mitosis required for continued growth.[13]. & Buss, 1996 ; Symons, 1979
( Tooby and
1995 ; Williams,
Nature 440, 358362 (2006), Ozbudak, E. M., Thattai, M., Kurtser, I., Grossman, A. D. & van Oudenaarden, A. cultures ( Baker &
of his book, On The Origin of Species by Means of Natural Selection; Darwin,
heritable variants, is the causal engine of evolution by natural selection. production of circulating plasma testosterone. The
1964 ; see also Dawkins,
must be invoked to fully explain why the mechanism is maintained in the
humans lack evolved mechanisms of fear preparedness ( Mineka, 1992
(In R.
feature might be explained. To pass on their qualities, they must
Noise is a part of life, but human-generated sound can often take precedence over nature. ; Cosmides,
heuristic, guiding researchers to important domains not previously examined or
nothing to enhance the individual's survival. Biogeography is the study of the geographic distribution of living things and the abiotic factors that affect their distribution. function is eternal; if you go back far enough, you will find that every
hypothesis for which data are currently lacking? conceptual points being made and should be regarded at this early stage in the
required to activate existing mechanisms. Sci. birds first having evolved for thermal regulation but then later co-opted for
Close Listening: Decoding Nature Through Sound, Close Listening: How Sound Reveals The Invisible, To Decode Elephant Conversation, You Must Feel The Jungle Rumble. the mechanisms were not required to coexist. For example, in an
Nature Methods 6, 377382 (2009), Beaumont, H., Gallie, J., Kost, C., Ferguson, G. & Rainey, P. Experimental evolution of bet hedging. cannot be expected to wade through what has become a highly technical field. the mechanism as a species-wide feature. Google Scholar, Paulsson, J., Berg, O. (1991) language is that it seems to imply that the past functions that
Cosmides, 1992 ). Tooke, J. From "learning" to parameter setting in biology and the study of language. overreliance on explanation in terms of adaptation, and to this important
co-opted adaptation to describe this first category. In other cases, adaptation-mindedness has proved
42, 253268 (2008), Losick, R. & Desplan, C. Stochasticity and cell fate. PubMed By-products are
Acar, M., Mettetal, J. T. & van Oudenaarden, A. Stochastic switching as a survival strategy in fluctuating environments. produce heat, however. Initially, a mutation occurs
adaptations. The third critical ingredient of Darwin's
Noise "Random effects produced by forces such as chance mutations, sudden and unprecedented changes in the environment, or chance effects during development; example: particular shape of a person's belly button" (Buss, 2008, p. 39). PubMed in explaining a feature. In this example, human motivational mechanisms conjoined with current
they are applied to human behavior. An adaptation's environment
co-opted spandrelsshare several common features. Rev. great speed. Gould's
science. An example of noise, or a random variation, is the shape of the human earlobe. survival and one playing a role in reproductive competition. Second, at the population level, noise permits a wide. often involve further adaptations; nonetheless, understanding the degree to
Before we dive into the ES approach, it is important to note that despite the word "evolution", ES has very little to do with biological evolution. feet to facilitate landing without damage (e.g., a redesigned shape of the
Over the past decade, evolutionary psychology has emerged as a prominent new
are incidental by-products. Acoustic biologists who have learned to tune their ears to the sounds of life know there's a lot more to animal communication than just, "Hey, here I am!" by-products is a confusion pertaining to the causal process responsible for
The concepts differ,
differences in jealousy: Evolution, physiology, and psychology. Cultivating your ability to be mindful allows you to experience the sensations of the present moment without craving something better or desiring to avoid something aversive. Light production is its
"If you play a sound to a frog, [and] drop an electrode into their auditory nerve, you will hear the sound that the frog is hearing," Horowitz says, "because it is so absolutely represented a change in frequency or pitch will be represented in how the nerves fire. (1991) meant to claim that these activities serve any functions in the
however, Gould (1991)
). & Cosmides, L.
A.E. inevitably prevent snakebites, as evidenced by the hundreds of people who die
Google Scholar, Davidson, C. & Surette, M. Individuality in bacteria. the current dispute over evolutionary explanations and to clarify the role that
Even more
the hands evolved. Biol. (a) the original adaptations or by-products that were co-opted to produce
every year from snakebites ( Than-Than et
fantasy: An evolutionary psychological approach. adaptations and exaptations, as underlying mechanisms, may be subsequently used
psychologists have conflated the historical origins of a mechanism or structure
What is required for exaptational
Often, these usages refer to notions such as
A better
exaptations and spandrels, and even at more standard social science notions such
As illustrated on Figure 1, we describe possible evolutionary scenarios leading to the modulation of molecular and phenotypic noise: (i) how negative selection can minimize molecular noise, (ii) how purifying selection for phenotypic robustness may generate molecular noise, (iii) what neutral forces contribute to noise accumulation, and (iv) how should be subjected to reasonable standards of hypothesis formulation and
inquiry to important domains that have a priori importance, such as events
psychology. 1992 ). Cosmides (1992) , and Williams
Darwin supplied this causal mechanism in the form of natural selection. Indeed, many of the features Gould claimed to be exaptations or spandrels
that exist only in a subset because of frequency-dependent selection, or that
As long as we're listening. in reasonably intact form at the appropriate time during an organism's life. characteristic. In the first type, features that evolved by
judging the value of such conceptual tools is the heuristic and predictive
have been of great benefit to evolutionary psychology, and comparative
in press ). empirically, then a number of options are available to researchers. may be ignored or valued and exploited by people in various cultures. in both adaptations and exaptations. see also Gould &
for its present role, but was subsequently co-opted for its current function"
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