chapter 4 genes evolution and behaviour

7/27/2019 Chapter 4 Genes Evolution and Behaviour

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Chapter 4 Genes Evolution and Behaviour

Genetic Influences

Chromosomes and Genes

How are physical characteristics passed on from parents to their offspring? o Hippocrates provided a semi-correct answer

Suggested that semen contains not body parts but a design for the formation of offspring

o Later Gregor Mendel confirmed this as a monk who researched garden peas Showed that heredity involves the passing on of specific organic factors and is

not a simple blending of the parents characteristics These specific factors might produce visible characteristics in the offspring or

might simply be carried for the possible transmission to another generation The offspring of one set of parents do not all inherit the same traits

o Early 20 th century geneticists made an important distinction between Genotype

The specific genetic makeup of an individual Eg. Like commands in a computer software program Present from conception and never change

Phenotype The observable characteristics produced by that genetic endowment Can be affected by other genes and the environment

How does genetic transmission pass on from parents to offspring? o Union of two cells, the egg from the mother and sperm from the father

Beginning of individual o The egg and sperm carry in them a material of heredity called chromosomes o Chromosome

Tightly coiled molecule of deoxyribonucleic acid(DNA) that is partly covered byprotein

So tightly coiled that if DNA was stretched out, it would be almost 2 meters long DNA portion of chromosome carries the hereditary blueprint in units called

genes sort of like giant computer file of info about characteristics etc. In humans every cell in the body except one type has 46 chromosomes

Exception is sex cell o Egg/sperm has 23 chromosomes

o At conception the egg and sperm combine to form a zygote(46 chromosomes) o Genes of chromosomes occur in pairs so the offspring receives one of each gene pair

from each parent o Every cell nucleus in your body has genetic code for entire body except sex cells o Alternative forms of a gene that produce different characteristics are called alleles


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o Genes code the production of proteins This affects our bodys development and functioning Responsible for controlling the structure of every cell and the chemical reactions

that are in those cells whether they are needed to keep life or changes inducedby maturation

Half of genes target brain structure and function Each gene carries code for a specific protein and when gene is activated, cell

produces protein At different points in development, in response to different

metabolic/environment factors, a gene may be activated and protein producedor already activated gene may be turned off decreasing a specific protein

Change with protein levels causes change within a neuron and the activities itdoes

Dominant Recessive and Polygenic Effects

What is the difference between dominant, recessive, and polygenic Genotypes and phenotypes are no identical If a gene is the pair received from the mother and father is dominant the characteristics that it

controls will be displayed If the gene is recessive , the characteristics will not show up unless the partner gene inherited

from the other parent is also recessive Even when hidden recessive genes are passed to their offspring In many cases, gene pairs combine to create a single phenotypic trait known as polygenic

transmission

o Complicates that people would be determined by 1 geneo Stresses the possible number of traits that can occur

Mapping the Genetic Code

Human Genome Project 2001, genetic map published Mapping of human genetic code was done by the International Human Genome Sequencing

Consortiumo Mapped genetic structure in every one of the 23 chromosome pairs o Found humans have less genes than expected 25000

Genetic Engineering

Describe the methods used in recombinant DNA research Advances in technology allows us to duplicate/modify the structure of genes themselves Recombinant DNA procedures


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Heredity means passage of characteristics from parents to offspring by way of genes Heritability means how much of the variation in a characteristic within a population can be

attributed to genetic differences o Note this means the variance in the trait across individuals and not the trait itself o If weight has a heritability coef of 0.6 then it means how much of that variation in

weight is attributable to genetic factors o Applies to only differences within a group and NOT between groups because if it is in

the same group the environmental factors can be counted out and then the coef wouldbe more meaningful

Knowing the level of genetic similarity in family members and relatives provides a basis forestimating the relative contributions of heredity and environment to a physical or psychologicalcharacteristic

If a characteristic has higher concordance /co-occurrence, in people who are high related toanother, then this shows a possible genetic contribution especially if they lived in differentenvironments

How are adoption and twin studies used to achieve heritability estimates? What have suchstudies shown?

o One research study is the adoption studyo A person who was adopted early in life is compared to some characteristics with his/her

biological parents and then with the adoptive parents with whom no genes are shared If biological parents had more similarities then genetic influence and vice versa

o Study with schizophrenia showed a hereditary link Twin studies are one of the more powerful techniques used in behaviour genetics Monozygotic twins develop from the same fertilized egg so they are genetically identical

Dizygotic(fraternal) twins develop from 2 fertilized eggs so they share 50% of their geneticendowment like any other brothers and sisters

A effective research method to examine concordance rates/behaviour similarities betweenidentical twins and fraternal twins if identical more similar than genetic factor is strong

o Find and compare sets of identical and fraternal twins who were separated early in lifeand raised in different environments

Adoption and twin studies led behavioural geneticists to conclude that psychologicalcharacteristics like intelligence, personality traits, psychological disorders all have a geneticcontribution

Environment and genes are related to criminal activity

Genetic Influences on Behaviour

Heredity, Environment and Intelligence

Main controversial question-to what extent are differences in intelligence due to genetic factorsand to what extent does environment determine differences in intelligence?

o Genetic argument-suppose intelligence is determined by genes


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Any 2 individuals with the same genes would have same test scores so thecorrelation between the test scores of identical twins would be +1; fraternaltwins share only half and therefore their correlation should be lower

To extend, the correlation between a parents test scores and his/her childrensscores should be about the same as that between siblings because a child only

gets half his genes from the parent o A study was done and identical twins separated early in life-different environment but

same genes; theyre correlation is almost as high as identical twins in the sameenvironment and higher than fraternal twins in the same environment

o The more genes in c ommon, the more similar theyre IQ o Findings show both environment and genes determine IQ but how do both interact to

affect intelligence?

Biological Reaction Range, The Environment, Personality and Intelligence

How does the concept of reaction range illustrate the interaction between heredity andenvironment

Reaction range helps us understand genetic environmental interactions o The reaction range for a genetically influenced trait is the range of possibilities( the

upper and lower limits) that the genetic code allows o Eg. Intelligence is genetically influenced does not mean that it is fixed at birth but means

that an individual inherits a range for potential intelligence that has upper and lowerlimits and the environmental effects will determine where the person falls within thereaction range

o We cannot determine the size of this range but studies suggest that it could be as large

as 15-20 points on the IQ scale- if this is the case then environmental factors would behighly significant

Behaviour Genetics and Personality

Hans Eysenck argued that personality differences could be traced to differences in braindevelopment or function

The personality of extraversion/introversion was argued to reflect differences in brain arousal First to suggest a biological basis for major personality traits Led other researchers to find a relationship between neuroticism and a gene allele that

increases the action of the neurotransmitter serotonin And a relationship between novelty seeking and a single gene allele that deceases the action of

the neurotransmitter dopamine Prominent personality trait theory Five Factor Model

o Five factor theorists like Robert McCrae and Paul Costa believe that individualdifferences in personality can be accounted for by variation along five broad personalitydimensions or traits known as the big five


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Extraversion/introversion(sociable, outgoing, adventuresome versus queit,inhibited, solitary)

Agreeableness ( cooperative, helpful, good natured versus antagonistic,uncooperative, helpful, suspicious)

Conscientiousness ( responsible, goal-directed, dependable versusundependable, careless, irresponsible)

Neuroticism (worrying, anxious, emotionally unstable versus well adjusted,secure, calm

Openness to experience (imaginative, artistically sensitive versus unreflective,lacking in intellectual curiosity)

Twin studies of heritability of the Big Five personality traits found heritability coef ranging from0;42 to 0;57 which is consistent of other studies indicates that 40-50% of the personalityvariations among people are attributable to genotype differences

Genetic factors account for a significant amount of a personality difference not as much as IQ

Study

A study compared personality traits in identical and fraternal twins who were raised together orreared apart

If identical twins reared in different environments by different families are as similar as thosereared together, a strong argument is made for the role of genetic factors

o This research design divided the variation among individuals on each personality traitinto 3 components

Variation attributable to genetic factors Variation due to a shared family environment among those reared together

Variation attributable to other factors such as unique individual experiences o Compared influence of these sources of variation by comparing personality test

correlations among 4 groups Identical twins reared apart/together Fraternal twins reared together/reared apart

o Studies shown that identical twins are far more similar in personality traits thanfraternal twins and reared together/apart makes little difference-family influence haslittle influence on personality differences

According to the results of the Minnesota Twin Study, what factors were the most important indetermining personality?

o One of the largest/best known studies wa the Minnesota Twin Study o Assessed more than 400 twins both reared apart and reared together but didnt

really affect the results o little shared experience within the same family environment family environment

accounted for little/no variation in any of the personality traits o Individuals unique experience like school experiences, social interactions, and individual

learning experiences accounted for 36-56% of the variation in personality traits


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o Results showed that genetic factors accounted for 39-58 personality trait scores o Within the same family, individual children have different experiences while growing up

and this collective experience shape personality Another study

o shows highest heritability coefficients >0.5 were found for attitudes toward readingbooks, abortion without restriction , playing organized sports, riding roller coasters,death penalty in general attitudes toward preservation of life, equality, and athleticismhad highest genetic component

o suggested rollercoaster gene or that certain inherited factors like physical characteristicsmay predispose individuals to prefer certain activities

o genetic influence has been reported for a tendency to abuse alcohol

Evolution and Behaviour

Define evolution and explain how genetic variation and natural selection produce adaptations

Evolutionary psychologyo Seeks to understand how behavioural abilities and tendencies have evolved over the

course of millions of years in response to environmental demands o Biologically based mechanisms

No behaviour by any organism can occur with this mechanism Receive input from the environment, process the information and respond to it We begin life with innate biologically based mechanisms that allow us to take in,

process and respond to information predisposing us to behave feel and think incertain ways

Allow us to have behaviour like aggression and sex roles

Evolution of Adaptive Mechanisms

Evolution

Change over time in the frequency with what particular genes-and the characteristics theyproduce- occur within an interbreeding population

As particular genes become more/less frequent in a population so do the characteristics theyinfluence

Some genetic variations arise in a population through mutations o Random events and accidents in gene reproduction during the division of cells o Help create variation within a populations physical characteristics which makes

evolution possible

Natural selection

According to Darwins principle of natural selection, characteristics that increase the likelihoo dof survival and ability to reproduce within a particular environment will be more likely to bepreserved in the population and therefore will become more common in the species over time


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Acts as a set of filters allowing survivors to become more common and non-survivors to becomeextinct

The filters also allow Neutral variations-aka variational noise- that neither facilitate nor impedefitness to pass through and be preserved in a population

o Eg. People differ in ability tolerate radiation today limited importance but affectsurvivability if a furutre nuclear war were to increase levels of radioactivity around theworld

Evolutionary Adaptations

Products of natural selection are called adaptations o Adaptations allow organism to meet recurring environmental challenges to their

survival, increasing reproductive ability o Natural selection is to pass on ones genes -why we might risk our lives for our kin o To humans

Organisms biology determines behavioural capabilities and behaviourdetermines survivability

Successful human behaviour evolved along with changing body o One theory is when apelike animals from trees needed to hunt in open plains, chances

of survival were greater for those who were capable of bipedal locomotion walking on2 legs

Freeing the hands allowed use of tools and weapons and hunting in groupsencouraged social organization

Social organization promoted roles like hunter in male and development of language and transmission of knowledge

o Women who were more sensitive had more kids survive social roles o Tool use, bipedal locomotion, social organizationo Greatest pressure to brain structure attention, memory, language, and thought

Progression from Australopithecus through Homo erectus to Neanderthal, the brain tripled insize

Todays human brain does not differ much from the stone age brain - the fact that we are moreadvanced is due to cultural evolution culture allows us to have important environmental inputto evolutionary mechanisms

Biological adaptation o Ability to learn language, repeat behaviours rewarded and suppress those that are

punished, reason logically Domain specific adaptations

o Designed to solve a particular problem like suitable mateo Suggest that the human mind is not an all purpose problem solver but a collection of

specialized independent modules that evolved to handle specific adaptive problems


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Evolutionary snapshot of human nature

Describe examples of human behaviour that suggest innate evolved mechanisms.Differentiate between remote and proximate causal factors

o Infants are born with innate ability to acquire any language spoken in the world-exposed

to Deaf children innate ability to acquire an sign language Language is central to human thought and communication

o Newborns Prewired to understand certain stimuli Eg. More responsive to pictures of human faces than facial features arranged

randomly Discriminate odour of mothers milk from that of other women Adaptations improve human bonding with caregivers

o At 1 week of age human infants show primitive math skills, discriminating between 2/3

objects Abilities improve with age in the absence of training Brain knows greater/less than judgements important in decision making

o Robert Hogan Established cooperative relationship with a group is important for survival and

reproductive success Thus, humans want to belong and fear rejection from the group social anxiety

may be an adaptive mechanism to protect against doing things that will get yourejected

o Basic set of emotions universally recognized-smiling is universal of happiness and

goodwill that gets positive reactions from others Emotions are important for social communication

o Personal adaptations to life occur through the law of learning Predisposed to learn

Evolutionary Psychology

Personality

According to evolutionary theorists, what is the origin of the basic personality traits? Evolutionary personality theory

o Where did personality traits come from o Current theory argues that human personality has a limited number of basic

dimensions/researchers argued that basic personality traits are found in all humanso David Buss-evolutionary personality theorist says they exist in humans because they

have helped us achieve two overriding goals: physical survival and reproduction of species extraversion and emotional stability is helpful for dominance and mateselection


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Lewis Goldberg suggests that we should ask 5 questions when interacting with another person o Is person X active and dominant or passive and submissive? Can i dominate X or will i

have to submit to x o Is person x agreeable and friendly or hostile and uncooperative o Can I count on X is X conscientious and dependable o Is X sand or crazy o How smart is X and how quickly can X learn and adapt

One issue could be the range of human personality

Mating systems and Parental Investment

Humans unlike fish invest more time in a few offspring-dichotomy What is meant by parental investment? Parental investment refers to the time, effort, energy, risk associated with caring successfully for

each offspring

Robert Trivers theory the parent who invests most in offspring will be more vigorouslycompeted for and will be more discriminating when choosing a mate

o Since female investment is high, they will be competed for and male investment is lowso males maximize fitness by producing many offspring with many different families most mammals are polgynous polygyny

o Since females can produce a limited number of offspring they need to choose mate o If both male and female investment is high-predict a monogamous mating system

Natural selection facours genes that lead to parents staying together Show little sexual dimorphism in size or strength

o Polyandry

Female mates with many males rare in mammals but in some fish species females compete with one another for males

o Polygynandry/promiscuity-all members mate with each other-found in primates A way to reduce competition for a mate and my help promote peace

What mating described by Trivers fits experience of human society?o Human female more investment polygynous single partner prolonged periods in life

How are male and female mate preferences similar? How are they different?o The most common/powerful mate preferences are all preferences that make the most

sense form an evolutionary perspective o Men + women want mutual attraction, dependability, emotional stability o Men place more on physical attractiveness and good health while women place greater

value on earning potential status, ambition and older men o Makes sense because young adult males rarely have the respect, status, access to

resources that are achieved by older, more established males-late 20s o Women like guys with symmetrical face and other signs of physical health

Suggests that he is free of parasites or genetic resistance to parasites and hashealthy development


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Peggy La Cerra assessed whether women might want men who has high parental investmento Did study and women rated men who were interacting positively with the child the

highest as a potential mate and rated the man ignoring the crying child the lowest o Man cleaning house is rated less attractive o Mens attractiveness ratings were the same across all conditions -good face and youth

Women want older guys and older guys want younger women

Altruism

What is the difference between cooperation and altruism Cooperation

o Situations in which one individual helps another and gains some advantage Help friend work you all benefit Adaptive value is clear-you accomplish more in groups than alone

Altruism

o One individual helps another but accrues a cost o Eg.a bird emits a call to warn off a predator warning helps other members of flock but

puts signalled in greater danger because it has revealed its location o 2 important theories

Kin selection theory Argues that altruism developed to increase survival of relatives

Mammals evolved living in small groups in which there was at leastsome genetic relatedness

Predicts that we should direct more acts of altruism towards relatives than nonrelatives

Theory of reciprocal altruism Altruism is long term cooperation Eg. One individual may help another but that assistance will be

reciprocated at some time in the future-if correct then the socialanimals should remember who has helped them in the past and shouldnot offer assistance to individuals who have failed to reciprocate

Requires stable social groupo These 2 theories are not incompatible

Kin selection explains why we are more likely to act altruistically towardgenetically related individuals and why we do not act the same way when

genetic relatedness decreases Reciprocity explains why we offer assistance to and request assistance from

nonkin Altruism does not always occur

Aggression

Evolutionarily what does aggression serve?


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Valued resources are limited eg. Shelter, food, desirable mates, a solution is to compete todetermine who has access to the resource

o Aggression developed as a means to protect ones mate, young, territory, food,resources, or gain access to resources

Which members of a group are usually the most aggressive? o As animals evolved they were able to recognize others and remember past encounters o Resulted in dominance hierarchies-established in initial encounters between animals if

the group is being formed or if a new member joins the group o Aggression can occur forming this hierarchy

Aggression makes sense-functions to divide limited resources among a group and those who aremost skilled in physical confrontation or forming social alliances gain the most

Pattern of aggression observed only among chimps and humans-forms male coalitions to attackothers as a group-lethal

How not to think about behaviour genetics and evolutionary psychology

Scientific issues o Adaptations are forged over a long period of time and we cannot be certain what the

environment was like back then therefore many conclusions are inferred o Fallacy of circular reasoning

Why does behavioural tendency X exist? Because of Environmental Demand Y How do we know that environmental demand Y existed? Because otherwise behaviour X would not have developed

o Not every human characteristic is because of natural selection o A capability evolved in the past for one reason may be adaptive for something else o Eg. Ability to discern shapes was advantageous for prehistoric hunters but few humans

today need to hunt to survive but shape discriminating capabilities are important forreading and letters

Insufficient weight to cultural learning factors-human culture evolves as both a cause and effectof brain and behavioural evolution-genes and environment affect each other over time

Genetic determinism o Idea that genes have invariant and unavoidable effects that cannot be altered-genes are

destiny o Not true-eg. The discovery that early diabetes has a genetic cause did not result in

medical science abandoning diabetic patients because nothing could be done butinstead the discovery allowed scientists to stop looking for nonexistent viral/bacterialcause freeing resources to increase understanding of the genetic basis and developways to compensate for the missing enzyme

One reason for the Human Genome Project is that there is a genetic cause for disease such asAlzheimers disease or a genetic predisposition such as for breast cancer


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Evolutionary theorists argue against the idea that if something is genetically based it is somehownatural and therefore right argue against themselves

o Conclusion is that people at the top of the social ladder are the most fit /best people o Referred as Social Darwinism

Genetic superiority of those at the top of the social hierarchy Another fallacy is evolution is purposive-has a plan

o There is no plan in evolutionary theory only adaptation to environmental demands andthe natural selection process that results

o Natures plan and social Darwinism has been used to support the morality of c ertainacts

You cannot use this as a basis in determining what is ethically appropriate Judgements of morality are most appropriately based on cultural standards and

philosophical considerations not biological imperatives

chapter 4 genes evolution and behaviour

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