Evolutionary psychology

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Evolutionary Psychology-UNIT 1Foundation of Evolutionary Psychologynsb

Evolution before DarwinJean Pierre Antoine de Monet de Lamarck was one of the first scientists to use the word biologie, thus recognizing the study of life as a distinct scienceLamarck believed in two major causes of species change: a natural tendency for each species to progress toward a higher form and, the inheritance of acquired characteristics.nsb

Baron Cuvier proposed a theory called catastrophism,according to which species are extinguished periodically by sudden catastrophes, such as meteorites, and then replaced by different species.

Biologists before Darwin also noticed the bewildering variety of species, some with astonishing structural similarities

Biologists noticed that such development was strikingly similar in species that otherwise seemed very different from one another. An unusual loop-like pattern of arteries close to the bronchial slits characterizes the embryos of mammals, birds,and frogsnsb

Many species possess characteristics that seem to have a purpose. The porcupine's quills help it fend off predators. The turtle's shell helps to protect its tender organs from the hostileforces of nature. The beaks of many birds are designed to aid in cracking nuts. This apparent functionality, so seemingly abundant in nature, also required an explanation.

A causal mechanism or process to explain these biological phenomena was needednsb

Darwin's Theory of Natural Selection Darwin wanted to determine how new species emerge, as well as how others vanish.Darwin wanted to explain why the component parts of animals-the long necks of giraffes, the wings of birds, the trunks of elephants--existed in those particular forms. And he wanted to explain the apparent purposive quality of those forms, or why they seem to function to help organisms accomplish specific tasks.nsb

He traveled the world as a naturalist on a ship, the Beagle, for a five-year period, from 1831 to 1836. During this voyage he collected dozens of samples of birds and other animals from the Galapagos Islands in the Pacific Ocean.

he discovered that the Galapagos finches, which he had presumed were all of the same species, actually, varied so much that they constituted different speciesnsb

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Darwin determined that these different finches had a commonancestor but had diverged from each other because of the localecological conditions on each island

Darwin wanted to account for change, of course, but perhapseven more important he wanted to account for why organismsappeared so well designed for their local environments.

Thomas Malthus' s An Essay on the Principle of PopUlation (published in 1798), which introduced Darwin to the notion that organisms exist in numbers far greater than can survive and reproduce.nsb

The result must be a "struggle for existence," in whichfavourable variations tend to be preserved and unfavourable ones tend to die out. When this process is repeated generation after generation, the end result is the formation of a new species.

Darwin's answer to all these puzzles of life was the theory of natural selection and its three essential ingredients: variation, inheritance, and selectionnsb

First, organisms vary in all sorts of ways, such as in wing length, trunk strength, bone mass, cell structure, fighting ability, defensive ability, and social cunning. Variation is essential for the process of evolution to operate-it provides the "raw materials" for evolution.

Second, only some of these variations are inherited-that is, passed down reliably from parents to their offspring, which then pass them on to their offspring down through thegenerations. Other variations, such as a wing deformity caused by an environmental accident, are not inherited by offspring. Only those variations that are inherited playa role in theevolutionary processnsb

The third critical ingredient of Darwin's theory is selection. Organisms with some heritable variants leave more offspring because those attributes help with the tasks of survival or reproduction. Eg

In an environment in which the primary food source might be nut-bearing trees or bushes, some finches with a particular shape of beak, for example, might be better able to crack nuts and get at their meat than would finches with other shapes of beaks. More inches who have beaks better shaped for nut cracking survive than those with beaks poorly shaped for nut cracking and thereby can contribute to the next generation .nsb

differential reproductive success, brought about by the possession of heritable variants that increase or decrease an individual's chances of surviving and reproducing, is the "bottom line" of evolution by natural selection .

Differential reproductive success or failure is defined by reproductive success relative to others. The characteristics of organisms who reproduce more than others, therefore, get passed down to future generations at a relatively greater frequency. Because survival is usually necessary for reproduction, it took on a critical role in Darwin's theory of natural selection.nsb

Darwin's Theory of Sexual SelectionHe observed several that seemed to contradict his theory of natural selection, also called "survival selection.

First he noticed weird structures that seemed to have absolutely nothing to do with survival; the brilliant plumage of peacocks was a prime example.

Darwin also observed that in some species, the sexes differed dramatically in size and structure.nsb

Darwin's Theory of Sexual SelectionIn contrast to the theory of natural selection, which focused on adaptations that have arisen as a consequence of successful survival, the theory of sexual selection focused on adaptations that arose as a consequence of successful mating.

2 Primary Means of Sexual Selectionintrasexual competitionintersexual selection nsb

Intrasexual competition is the competition between members of one sex, the outcomes of which contributed to mating access to the other sex. Eg.The prototype of intrasexual competition is two stags locking horns in combat. The victor gains sexual access to a female either directly or through controlling territory or resources desired by the female. The loser typically fails to mate. Whatever qualities lead to success in the same-sex contests, such as greater size, strength, or athletic ability, will be passed on to the next generation by virtue of the mating success of the victorsnsb

intersexual selection, or preferential mate choice. If members of one sex have some consensus about the qualities that are desired in members of the opposite sex, then individuals of the opposite sex who possess those qualities will be preferentially chosen as mates.

Those who lack the desired qualities fail to get mates. In this case, evolutionary change occurs simply because the qualitiesthat are desired in a mate increase in frequency with the passing of each generation. Darwin called the process of intersexual selection female choice because he observed that throughout the animal world, females of many species were discriminating or choosy aboutwhom they mated with .nsb

Although Darwin believed that natural selection and sexual selection were two separate processes, it is now known that they stem from the same fundamental process: differentialreproductive success by virtue of heritable differences in design.nsb

Evaluation of Darwins theory and Post Darwinian approachesnatural and sexual selection are not the only causes of evolutionary change. Some changes, for example, can occur because of a process called genetic drift, which is defined as random changes in the genetic makeup of a population.

Random changes come about through several processes, including mutation (a random hereditary change in the DNA),founder effects, and genetic bottlenecks.nsb

founder effect, which occurs when a small portion of a population establishes a new colony and the foundersof the new colony are not entirely genetically representative of the original population.

genetic bottlenecks, which happen when a population shrinks, perhaps owing to a random catastrophe such as an earthquake. The survivors of the random catastrophe carry only a subset of the genes of the original populationnsb

Second, evolution by natural selection is not forward-looking and is not "intentional."The giraffe does not spy the juicy leaves stirring high in the tree and "evolve" a longer neck.

Another critical feature of selection is that it is gradual, at least when evaluated relative to the human life span. The short-necked ancestors of giraffes did not evolve long necks overnight or even over the course of a few generationsnsb

there can be long periods of no change, followed by a relatively sudden change, a phenomenon known as "punctuated equilibrium" (Gould &Eldredge, 1977). But even these "rapid" changes occur in tiny increments each generation and take hundreds or thousands of generations to occur.

One objection was that Darwinian evolution lacked a coherent theory of inheritance. Darwin himself preferred a "blending" theory of inheritance, in which offspring are mixtures of their parents, much like pink paint is a mixture of red and white paintnsb

Another objection was that some biologists could not imagine how the early stages of the evolution of an adaptation could be useful to an organism. How could a partial wing helpa bird, if a partial wing is insufficient for flight?

it is sufficient to note that partial forms can indeed offer adaptive advantages; partial wings, for example, can keep a birdwarm and aid in mobility for catching prey or avoiding predators, even if they don't afford full flight. This objection to Darwin's theory is therefore surmountable .nsb

The Modern Synthesis: Genes and Particulate InheritanceAn Austrian monk named Gregor Mendel showed inheritancewas "particulate," and not blended.

That is, the qualities of the parents are not blended with each other, but rather are passed on intact to their offspring in distinct packets called genes. Furthermore, parents must be born with the genes they pass on; they cannot be acquired by experience.nsb

Genotypes, in contrast, refer to the entire collection of genes within an individual. Genotypes, unlike genes, are notpassed down to offspring intact. Rather, in sexually reproducing species such as our own, genotypes are broken up with each generation. Thus, each of us inherits a random half of genes from our mother's genotype and a random half from our father's genotype.

The unification of Darwin's theory of evolution by natural selection with the discovery of particulate gene inheritance culminated in a movement in the 1930s and 1940s calledthe "Modern Synthesis"

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The Ethology MovementThe evolution of behavior, however, has historically been more difficult for scientists and lay people to imagine. Behavior, after all, leaves no fossils!!

Darwin clearly believed his theory of natural selection as being just as applicable to behavior, including social behavior, as to physical structures. Several lines of evidence support this view. First, all behavior requires underlying physical structuresnsb

Bipedal locomotion is a behavior, for example, and requires the physical structures of two legs and a multitude of muscles to support those legs while the body is in an upright position.

Second, species can be bred for certain behavioural characteristics using the principle of selection.

The first major discipline to form around the study of behavior from an evolutionary perspective was the field of ethology, and one of the first phenomena the ethologists documented was imprinting.

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Ducklings imprint on the first moving object they observe in life-forming an association during a critical period of development. Usually this object is the duck's mother. After imprinting, the baby ducks follow the object of their imprinting wherever it goes.

This form of learning, however, is "preprogrammed" and clearly part of the evolved structures of the duckling's biology.

Lorenz (1965) started a new branch of evolutionary biology calledethology, and imprinting in birds was a vivid phenomenon used to launch this new field. Ethology is defined as "the study of the proximate mechanisms and adaptive value of animal behaviornsb

4 issues of ethology1.the immediate influences on behavior (e.g.,the movement of the mother)

2. the developmental influences on behavior (e.g., the events during the duck's lifetime that cause the behaviour)

3. the function of behavior, or the "adaptive purpose" it seems to fulfill (e.g.,keeping the baby duck close to the mother, which helps it to survive),

4. evolutionary or phylogenetic origins of behavior (e.g., what sequence of evolutionary events led to the origins of an imprinting mechanism in the duck).nsb

Ethologists developed an array of concepts to describe what they believed to be the innate properties of animals. Fixed action patterns, for example, are the stereotypic behavioural sequences an animal follows after being triggered by a well-defined stimulus .

Once a fixed action pattern is triggered, the animal performs it to completion. Showing certain male ducks a wooden facsimile of a female duck, for example, will trigger a rigid sequence of courting behavior.

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1.many descriptions acted more as "labels" for behaviour patterns and did not really go very far in explaining them

2.ethologists tended to focus on observable behavior-much like their behaviourist counterparts- and so did not look "inside the heads" of animals to the underlying mechanismsresponsible for generating that behavior

3. although ethology was concerned with adaptation (one of the four critical issues listed by Tinbergen), it did not develop rigorous criteria for discovering adaptationsIssues with the ethology movementnsb

William D. Hamilton reasoned that classical fitness-the measure of an individual's direct reproductive success in passing on genes through the production of offspring-was too narrow to describe the process of evolution by selection.He theorized that natural selection favours characteristicsthat cause an organism's genes to be passed on, regardless of whether the organism produces offspring directly.Parental care-investing in your own children-was reinterpreted as merely a special case of caring for kin who carry copies of your genes in their bodies. An organism can also increase the reproduction of its genes by helping brothers, sisters, nieces, or nephews to survive and reproduce.

The Inclusive Fitness Revolutionnsb

Technically, inclusive fitness is not a property of an individual or an organism but rather a property of its actions or effects. Thus, inclusive fitness can be viewed as the sum of an individual's own reproductive success (classical fitness) plus the effects the individual's actions have on the reproductive success of his or her genetic relatives

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you might try to ensure the well-being of the "vehicle" or body in which you reside (survival).2. you might try to induce the vehicle to reproduce3. you might want to help the survival andreproduction of vehicles that contain copies of you.gene's eye thinking.nsb

Reliability- Does the mechanism regularly develop in most or all members of the species across all "normal" environments and perform dependably in the contexts in which it is designed to function

Efficiency -Does the mechanism solve a particularadaptive problem well

Economy -Does the mechanism solve the adaptive problemwithout extorting huge costs from the organismWhat accounts for adaptationnsb

The first was the theory of reciprocal altruism among non kin-the conditions under which mutually beneficial exchange relationships or transactions could evolve

parental investment theory, which provided a powerful statement of the conditions under which sexual selection would occur for each sex (1972).

The third was the theory of parent-offspring conflict-the notion that even parents and their progeny will get into conflictsTrivers's Seminal Theoriesnsb

Misunderstanding 1: Human Behavior Is Genetically Determined

Misunderstanding 2: If It's Evolutionary,We Can't Change It

Misunderstanding 3: Current MechanismsAre Optimally DesignedCOMMON MISUNDERSTANDINGSnsb

Genetic determinism is the doctrine that argues that behavior is controlled exclusively by genes, with little or no role for environmental influence .

Human behavior cannot occur without two ingredients: (1) evolved adaptations and (2) environmental input that triggers the development and activation of these adaptations .

Misunderstanding 1: Human Behavior Is Genetically Determinednsb

A second misunderstanding is that evolutionary theory implies that human behavior is impervious to change

knowledge of our evolved social psychological adaptations along with the social inputs that activate them gives us tremendous power to alter social behavior, if that is the desired goal

Misunderstanding 2: If It's Evolutionary,We Can't Change Itnsb

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The concept of adaptation, the notion that mechanisms have evolved functions does not mean, however, that the current collection of adaptive mechanisms that make up humans is inany way "optimally designed.

Because evolutionary change occurs slowly, requiring thousands of generations of recurrent selectionpressure, existing humans are necessarily designed for the previous environments of which they are a product. Stated differently, we carry around a Stone Age brain in a modemEnvironment. This happens because of evolutionary time lags.Misunderstanding 3: Current MechanismsAre Optimally Designednsb

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All adaptations carry costs. Selection favours a mechanism when the benefits outweigh the costs relative to other designsMisunderstanding 3: Current MechanismsAre Optimally Designednsb

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Three Theories of the Origins of Complex Adaptive Mechanisms

Creationism

Seeding theory

Evolution by natural selection

THE ORIGINS OF HUMAN NATUREnsb

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Creationism--the idea that a supreme deity created all of the plants and animals, from the largest whales to the smallest plankton in the ocean, from the simple single-celled amoebasto the complex human brainNot scientific asit cannot be tested because specific empirical predictions do not follow from its major premise.creationism has not guided researchers to any new scientific discoveriescreationism has not proved useful as a scientific explanation for already discovered organic mechanisms

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According to seeding theorists, life did not originateon earth.

the seeds of life arrived on earth via a meteorite. extraterrestrial intelligent beings came down from other planets or galaxies and planted the seeds of life on earth

Seeding theory is in principle testable. We can study meteorites for signs of life, which would lend plausibility to the theory that life originated elsewhere.

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no solid scientific evidence on earth that such "seedings" have taken place.

Seeding theory has not led to any new scientific discoveries, nor has it explained any existing scientific puzzles

It simply pushes the causal explanation for origins of life back in time. If the earth was really seeded by extraterrestrial beings, what causal processes led to the origins of these intelligent beings

Criticisms of seeding theorynsb

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Although evolution by natural selection is called a theory, its fundamental principles have been confirmed so many times-and never disconfirmed-that it is viewed by most biologists as a fact

The components of its operation-differential reproduction due to inherited design differences-have been shown to work in both the laboratory and the wild.evolution by natural selection.nsb

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1.it organizes known facts

2.it leads to new predictions

3. it provides guidance to important domains of scientificinquiry.

Evolution by natural selection is the only known scientific theory that can explain the astonishing diversity of life we see around us today .

It is a profound scientific theory as nsb

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Adaptations

by-products

random effectsThe Three Products of Evolutionnsb

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An adaptation may be defined as an inherited and reliably developing characteristic that came into existence through natural selection because it helped to solve a problem ofsurvival or reproduction during the period of its evolution (after Tooby & Cosmides, 1992, pp. 61-62; see also Thornhill, 1997).Adaptationnsb

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Thus,1.An adaptation must have genes "for" that adaptation. Those genes are required for the passage of the adaptation from parents to children; hence adaptations have a genetic basis .2. Most adaptations, of course, cannot be traced to single genes but rather are products of many genes.3. The fact that genes are required for adaptations, however,does not mean that human behavior is "genetically determined4. Past environments selected the genes we have today; environments during a person's lifetime are necessary for the proper development of adaptations, and current environments are responsible for activating adaptations once they have developed

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5. is, to qualify as an adaptation it must emerge at the appropriate time during an organism's life in reasonably intact form and hence be characteristic of most or all of themembers of a given species (There are important exceptions to this, such as mechanisms that exist in only one sex or in a specific subset of the population )6. The reliably developing feature of adaptations does not mean that the adaptation must appear at birth . Many adaptations develop long after birth7. Characteristics that are transient, temporary, easily perturbed by the environment, or appear in only a few members of a species are not reliably developing and hence do not meetthe definitional standards for adaptations.

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8. Adaptations are fashioned by the process of selection. Selection acts as a sieve in each generation, filtering out the many features that do not contribute to propagation and letting through those that do .9.This sieving process recurs generation after generation,so that each new generation is a bit different from its parent generation. This process of natural selection is necessary for the creation of adaptations.10. Those characteristics that make it through the filtering process in each generation do so because they contribute to the solution of an adaptive problem of either survival or reproduction better than alternative (competing) designs existing in the population

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11.The function of an adaptation refers to the adaptive problem it evolved to solve, that is, precisely how itcontributes to survival or reproduction.12. The function of an adaptation is typically identifiedand confirmed by evidence of "special design," whereby the components or "design features all contribute in a precise manner to solve a particular adaptive problem

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Initially a mutation, a spontaneous change in the structure of a piece of DNA, occurs in a single individualMutations are thought to arise from mistakes in the replication of DNAAlthough most mutations hinder survival or reproduction, some, by chance alone, end up helping the organism survive and reproduceIf the mutation is helpful enough to give the organism a reproductive advantage over other members of the population, it will be passed down to the next generation ingreater numbersWhat causes adaptationnsb

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In the next generation, therefore, more individuals possess the characteristic that was initially a mutation in a single person

Over many generations, if it continues to be successful, the mutation will spread to the entire population, so every member of the species will have it.

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The environment of evolutionary adaptedness, or EEA, refers to the statistical composite of selection pressures that occurred during an adaptation's period of evolution responsible for producing the adaptation (Tooby & Cosmides, 1992)Stated differently, the EEA for each adaptation refers to the selection forces, or adaptive problems, that were responsible for shaping it over deep evolutionary timeThe EEA for the eye, for example, refers to the specific selection pressures that fashioned each of the components of the visual system over hundreds of millions of years

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The key point is that the EEA does not refer to a specific time or place, but rather to the selection forces that are responsible for shaping adaptations.

The adaptation's period of evolution refers to the time span during which it was constructed, piece by piece, until it came to characterize the universal design of the species.

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The evolutionary process also produces by-products of adaptationsBy-products are characteristics that do not solve adaptive problems and do not have functional design.They are "carried along" with characteristics that do have functional design because they happen to be coupled with those adaptations, just as the heat from a light bulb is a by-product of design for light.By-productsnsb

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eg,. human belly button

There is no evidence that the belly button, per se, helps humans survive or reproduce.

Rather, the belly button is a by-product of something that is an adaptation-namely, the umbilical cord that providedfood to the growing fetus

The hypothesis that something is a by-product of anadaptation, therefore, requires identifying the adaptation of which it is a by-product and the reason why its existence is associated with that adaptation

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Random effects can be produced by forces such as mutations, sudden and unprecedented changes in the environment, or accidents during developmentThese random effects sometimes harm the smooth functioning of an organismSome random effects are neutral-they neither contribute to nor detract from adaptive functioning-and some are beneficial to an organism

Noise is distinguished from incidental by-products in that it is not linked to the adaptive aspects of design features but rather is independent of such features. Noise also tends not to be species typicalnoise or random effectsnsb

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General Evolutionary Theory.

Middle-Level Evolutionary Theories

Specific Evolutionary Hypotheses.Levels of Evolutionary Analysis in Evolutionary Psychologynsb

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The first level of analysis is general evolutionary theory

In its modem form, evolution by natural selection is understood from the "gene's eye perspective-differential gene replication is the engine of the evolutionary process by which adaptations are formed

At this general level, even though we talk about evolutionary "theory," it is widely accepted by biological scientists as factGeneral Evolutionary Theory.

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Most of the research in evolutionary psychology proceedsfrom the assumption that evolutionary theory is correct, but the research does not test that assumption directly.

There are observations that could, in principle, falsify general evolutionary theory. If scientists observed complex life forms that were created in time periods too short for natural selection to have operated

If scientists observed complex life forms that were created in time periods too short for natural selection to have operated (e.g., in seven days), then the theory would be proved false

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If scientists discovered adaptations that functioned for the benefit of same-sex competitors, then the theory would be proved false (Darwin, 1859; Mayr, 1982; Williams, 1966). No such phenomena have ever been documented.

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Trivers's theory of parental investment and sexual selectionThese middle-level theories are still fairly broad, covering entire domains of functioning

Trivers's theory of parental investment as the driving force behind sexual selection.This theory, which is itself an elaboration of Darwin'sown theory of sexual selection (1871), provided one of the key ingredients for predicting the operation of mate choice and intrasexual competition (competition betweenmembers of the same sex)Middle-level evolutionary theoriesnsb

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Trivers argued that the sex that invests greater resources in its offspring (often, but not always, the female) will evolve to be more choosy or discriminating in selecting a mate

The sex that invests less in offspring, in contrast, will evolve to be less choosy and more competitive with members of its own sex for sexual access to the valuable, high-investing opposite sex.

The fundamental tenets of Trivers's theory have been strongly supported by empirical evidence from a variety of species

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In some species, for example, the female implants her eggs in the male, and he is the one who carries the offspring until they are born. In species such as the Mormon cricket, poison arrow frog, and pipefish seahorse, for example, males invest more than females in this way

This so-called "sex-role reversed" species supports Trivers's theory, showing that it is not "maleness" or "femaleness" itself that causes the sex difference in choosiness; rather, it is therelative parental investment of the two sexes.

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Eg, One hypothesis that has been advanced for humans,for example, is that women have evolved specific preferences for men who have resources to offerBecause women invest heavily in children, they have evolved to be choosy when they pick matesthe content of women's choices should reflect whatever has historically increased the survival and reproduction oftheir childrenTherefore, women are hypothesized to have evolved mate preferences for men who are both able and willing to contribute resources to them and their childrenSpecific Evolutionary Hypotheses.nsb

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This specific evolutionary psychological hypothesis can be tested empiricallyScientists can study women across a wide variety of cultures and determine whether they in fact prefer men who are both able and willing to contribute resources to them and their children.On the basis of the hypothesis that women prefer men who have a lot of resources to offer, we could make the following predictions

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Women will value in men specific qualities known to be linked with the acquisition of resources such as social status, intelligence, and somewhat older agein a singles bar, women's attention, as measured by eye gaze, will be drawn more to men who appear to have resources than to men who do not;women whose husbands fail to provide economic resources will be more likely to divorce them than women whose husbands do contribute economic resources.The value of the hypothesis rests with the scientific tests of predictions derived from it.

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1.All Species Have a Nature--male lion's nature to walk on four legs, grow a large furry mane, and hunt other animals for food.2. Humans also have a nature-qualities that define us as a unique species-and all psychological theories imply its existence. All psychological theories require as their core fundamental premises about human natureTHE CORE OF HUMANNATURE :FUNDAMENTALS OF EVOLVEDPSYCHOLOGICAL MECHANISMSnsb

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Because evolution by selection is the only known causal process that is capable of producing the fundamental components of that human nature, all psychological theories are implicitly or explicitly evolutionary

If humans have a nature and evolution by selection is the causal process that produced that nature, then the next question is: What great insights into human nature can be provided by examining our evolutionary origins

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evolutionary psychology focuses more narrowly on those parts of evolution that are psychological-the analysis of the human mind as a collection of evolved mechanisms, the contexts that activate those mechanisms, and the behavioursgenerated by those mechanisms

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An evolved psychological mechanism is a set of processes inside an organism with the following properties: 1. An evolved psychological mechanism exists in the form that it does because it solved a specific problem of survival or reproduction recurrently over evolutionary history.2. An evolved psychological mechanism is designed to take in only a narrow slice of information.3. The input of an evolved psychological mechanism tells an organism the particular adaptive problem it is facing.4.The input of an evolved psychological mechanism is transformed through decision rules into output.

Definition of an Evolved Psychological Mechanismnsb

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5. The output of an evolved psychological mechanism can be physiological activity, information to other psychological mechanisms, or manifest behavior.

6. The output of an evolved psychological mechanism is directed toward the solution to a specific adaptive problem.

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Evolved Psychological MechanismsAn evolved psychological mechanism EPM exists in the form that is does because it solved a specific adaptive problem.Problem: whos my mommy?Example: Facial recognition -- newborn babies preferentially look at human faces.Important for recognizing kin.

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EPMsAm EPM can take the form of either a physiological activity, cognitive processing or behavior.The EPM is directed towards solving the adaptive problem.Important Point: EPMs that led to effective solutions in the past may no longer be effective now (vestigial).Example: piloerrection (I.e. goose bumps)

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EPMsAm EPM can take the form of either a physiological activity, cognitive processing or behavior.The EPM is directed towards solving the adaptive problem.Important Point: EPMs that led to effective solutions in the past may no longer be effective now (vestigial).Example: piloerrection (I.e. goose bumps)

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Problems Faced by Ancestral HumansProblems of Survival: Getting the organism to a point where it is capable of reproducing.Problems of Mating: Selecting, attracting and retaining a mate long enough to reproduce.Problems of Parenting: Helping offspring survive long enough that they are capable of reproducing.Problems of aiding genetic relatives: Tasks relevant to assisting non-descendent kin.

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ExampleImagine a population of omnivores that lacked the capability to digest rancid meat.The byproducts of bacterial activity in rancid meat are therefore toxic to this species.Imagine that this species had no EPM to stimulate avoidance of rancid meat.Each individual would have to learn through trial and error what smells, tastes etc signaled that meat was not fit for consumption.Now imagine that certain individuals were born with an aversion to the smell of rancid meat.Which individuals would have a higher fitness?

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Human Survival ProblemsFood selection: The most general problem in food selection is how to obtain adequate amounts of calories and essential vitamins.However, we must also avoid poisoning ourselves.Plants have adapted toxins that help reduce the odds that the plant will be eaten.Hypothesis: humans have evolved taste preferences to avoid toxic materials.How do we test this?

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Taste AversionsEvidence suggests that the materials that smell and taste bad to humans are also the materials that are potentially harmful to us.Broccoli and brussel sprouts contain allylisothiocynate which can be toxic in children (Nesse & Williams 1994)We have adaptive mechanisms for removing harmful materials from our body.Vomiting.

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Morning SicknessThe percentage of women who experience morning sickness has been reported to be anywhere from 75 89%. However, estimates suggest that the actual % is near 100.Hypothesis: Morning sickness is an adaptation to avoid consuming teratogens during the critical period in the development of the fetus.Evidence: The foods that pregnant women report to be most nauseating are correlated with high levels of toxins.Evidence: Morning sickness occurs at the same time that the fetus is most vulnerable to toxins.Evidence: Morning sickness decrease around the same time that the period critical for fetal development has passed.

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Morning SicknessRemember, an adaptation must confer an increase in fitness.Hypothesis: Women who do not experience morning sickness will be more likely to have problems during their pregnancy.Evidence: Women who do not experience M.S. are 3 times more likely to experience a spontaneous abortion (Profet, 1992)

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Human FearsFear can be viewed as an adaptive response to avoid situations that may lead to injury or death.Have humans evolved adaptive fear responses to specific stimuli? Or do humans learn fear responses through conditioning?

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Common Fears and PhobiasThe majority of reported fears and phobias involve:Spatial stimuli: heights, confined spacesSpecific animals: snakes, bats, spidersThe darkPublic speakingThere have been very few reported phobias of electricity, cars, busses, power tools, wood stoves, lawn mowers, mountain bikes, X-ray machines, cell phones etc

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Prepared FearsMineka (1983) observed that rhesus monkeys raised in captivity did not show a fear response when confronted with a snake.If these monkeys were shown videos of other monkeys displaying fear in the presence of a snake the subject monkeys quickly acquired the same fear response (same for crocodile). If captive raised monkeys were shown a video of monkeys displaying fear in the presence of a pot of flowers the subject monkeys did not acquire a fear response to flower pots (same for rabbit).

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EPMs can lead to creativityEPMs are not rigid instincts, but can change and develop in the species according to the environment.Example: Language has pidgins and creoles that have developed in environments where there was no existing language.

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Core Tenets of Evolutionary Psychology

1. All behavior is a function of psychological mechanisms + input to those mechanisms

Core Tenets of Evolutionary Psychology2. All psychological mechanisms, at some basic level, originate from evolutionary processes

Core Tenets of Evolutionary Psychology3. Natural and sexual selection are the most important evolutionary processes responsible for creating psychological mechanisms

Core Tenets of Evolutionary PsychologyAll Species have a Nature

Core Tenets of Evolutionary Psychology4. Evolved psychological mechanisms can be described as information processing devices.

InputsDecision RulesOutputs

Core Tenets of Evolutionary Psychology5. Evolved psychological mechanisms are instantiated in the brain.

Evolved Psychological Mechanisms Provide Nonarbitrary Criteria for "Carving the Mind at Its joints.Evolved Psychological Mechanisms Tend to Be Problem Specific.Humans Possess Many Evolved Psychological Mechanisms.The Specificity, Complexity, and Numerousness of Evolved Psychological Mechanisms Give Humans Behavioral Flexibility.Beyond Domain-Specific Psychological MechanismsImportant Properties of Evolved Psychological Mechanismsnsb

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Aren't the human behaviours we observe caused by learningand culture, not evolution? Aren't human behaviours the product of nurture, not nature?According to definition to evolved psychological mechanism-environments featuring recurrent selection pressure over deep time formed each mechanism;environmental input during a person's development is necessary for the emergence of each mechanismenvironmental input is necessary for the activation of each mechanismLearning, Culture, and Evolved Psychological Mechanismsnsb

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Evolved" is not the opposite of "learnedEnvironment of Evolutionary Adaptedness (EEA)

Learning, requires structures in the brain---evolved psychological mechanisms-that enable them to learn: "after all, 3-pound cauliflowers do not learn, but 3-pound brains do" (Tooby & Cosmides,2005, p. 31)

identify the nature of the underlying learning mechanisms that enable humans to change their behavior as a consequence of environmental input

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Consider comparisons between incest avoidance, food aversion and prestige criteria-

Inputs are different for each

operates on the basis of inputs from different set of cues

has different functional outputs

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Comparing Individuals within a SpeciesComparing the Same Individuals in Different ContextsExperimental MethodsMETHODS FOR TESTINGEVOLUTIONARY HYPOTHESESnsbComparing Different SpeciesComparing Males and Females

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METHODS FOR TESTINGEVOLUTIONARY HYPOTHESESnsb

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Esssay by Donald Symons :-

describe the adaptationist program in biologytry to show how this program can be applied fruitfully to human psychological adaptationsillustrate how social scientists, whose goal is to illuminate phenomena that are not themselves adaptations, can use evolutionary psychology to guide their researchargue that no approach to human behavior can be simultaneously psychologically agnostic and genuinely Darwinian

The Use and Misuse of Darwinismnsb

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Education

Evolutionary psychology