Ev psych: WS/Quiz review

True or false: The reason a species is the way it is TODAY is because of natural selection happening NOW

False

True or False: Evolutionary psychology emphasizes the utility of explanation at the ultimate/computational level of analysis

True

True or False: Two mechanisms can differ on the implementational level of analysis, but be identical on the computational level of analysis.

True

Differences between autism spectrum & neurotypical

most likely noise

What is represented by the entire denominator?

variation of a phenotypic trait within a population

Imagine that nowadays some people will end up in safe environments and some people will end up in dangerous environments. Imagine further that there are cues present in the child's environment that reliably predict what kind of environment they will end up in as an adult. Knowing this and only this, what would Life History Theory predict about how a mechanism in children today should use this information?

(Careful) The key difference between question 3 and 4 is the time frame. Natural selection takes time. Because this question specifies only that this information is available and predictive NOW, the mechanism should NOT be designed to use this information (yet).

In lecture, we learned that most adaptations show little heritability. Why is that?

(Heritability is population dependent and NOT rigid; it is useful as a statistical concept to show the approximate degree of variation in a phenotypic trait WITHIN a population that is due to genetic variation between individuals in THAT population.) Mutation causes genetic variation, when a trait goes to fixation (because it is adaptive) the variation is erased.

How does the concept of 'design constraints' as discussed in lecture inform our expectations about the kinds of design features adaptations should have? Should we expect adaptations to have all potentially beneficial design features? Should we expect adaptations to be 'successful' all the time?

-it allows us to specify types of design constraints (material constraints, phylogenetic history constraints, informational constraints, and computational constraints) & not think about adaptations as only relating to selection pressures (after all, adaptations don't "know" these!) -we should not expect adaptations to have all potentially beneficial design features (only that they have enough to shed light on design evidence of given adaption theory) -no, EEA dependent

Try to write out your model (in math, in computer code, in 'pseudo code' or in whatever kind description you want.)

2 alleles at a locus: p + q mutation: p --> q & q --> p P = proportion of p in population Pt+1 = Pt + m (defining system as P + mutation) -m ~U (-1, 1) to see relationship b/w p + q just governed by mutation, over time (observe variance) can also add % for selection to code (Pt+1 = Pt + m + .01) & again see if graph goes to fixation when replot -- OR spreadsheet (with generation in A, M% 1) insert P formula (first generation, then iterate over many generations) see random change over time add in 0.01 (selection) --> see what trending toward

Imagine you measure a large population and get a very precise estimate of the heritability of intelligence in this population (say, 95%). What does this imply? A)That most of the differences in intelligence between people in this population are dues to differences in their genes B)That intelligence is hard to modify by changing the environment C)That intelligence should be highly heritable in a different population in a different environment D)All of the above are correct implications E)None of the above are correct implications

A

Which of the following are reasons to expect sexually dimorphic adaptations? A)Ancestral men and women faced different fitness-relevant problems B)Modern men and women are treated differently by society C)Modern men and women are treated the same by society D)None of the above: we should never expect sexually dimorphic adaptations

A (In the same way that you would predict sexual monomorphism (no sex-differentiation) where ancestral men and woman faced the same fitness-relevant problem, you would predict sexual dimorphism where ancestral men and women faced different problems.)

The evolution of sexual reproduction is theorized to mostly be driven by selection for: A)Avoiding pathogens B)Maximizing variability between offspring (not 'putting all your eggs in one basket') C)More rapid adaptation D)B & C are both correct E)None of the above

A (Remember that asexual cloners are vulnerable to pathogens and parasites that adapt to the cloners' genome. Sexual reproduction mixes the genes of different individuals, making it harder for pathogens and parasites to specialize on the personal genome of the sexual reproducer.)

Sometimes selection is frequency dependent, that is, the strength and direction of selection depends on the frequency of the trait in the population. Think of the effect of pathogens on the frequency of blood types in humans. Which of the following statements below is accurate? A)Blood types are under positive selection when rare & negative selection when common B)Blood types are under negative selection when rare & positive selection when common C)Blood types are under positive selection when rare & positive selection when common D)Blood types are under negative selection when rare & negative selection when common E)None of the above: Blood type does not solve an adaptive problem regarding pathogens

A (When an allele is rare is less of a target for pathogens than its alternatives, so it has a selective advantage (is under positive selection). When an allele is common it is more of a target for pathogens than its alternatives, so it has a selective disadvantage (is under negative selection).)

Which mutation to a gene on the Y chromosome in humans (at least initially) spread via natural selection: A)Mutation A which increases the odds of having a daughter B)Mutation B which increases the odds of having a son C)Mutation C which keeps the odds of having a son or daughter equal D)None of the above: Natural selection will not operate on any of these mutations because they are on the Y chromosome

B

Which of the following mutations would be selected by natural selection (all else equal): A) Mutation A causes the organism to live longer, but has no effect on reproduction B) Mutation B causes the organism to die younger, but doubles her average number of offspring C) Mutation C causes the organism to reduce her own reproduction so that there is less competition for food in the community D) Mutation D causes the organism to be happier, but has no effect on reproduction E) All of the above

B

Imagine a species that had a complex trait, like a hand, that had a genetic basis spanning dozens of genes. Which of the following statements is most likely to be true? A)Those genes all emerged at the same time and spread to fixation together B)Those genes emerged over time and spread to fixation in pieces C)Both A & B are equally likely to be true D)None of the above: there is a one-to-one mapping of genes to traits

B (It would be extremely unlikely for a whole set of genes to arise at the same time and to act in concert. It is far more likely that the genes emerged over time and incrementally contributed to the organization of the trait, each spreading to fixation because of the fitness benefits they individually conferred.)

Adaptations are solutions to adaptive problems, byproducts are traits associated with adaptations, and noise refers to traits unreliably with adaptations. People in industrialized nations can often recognize many makes and models of cars. Which of the following is more likely? A)This trait is an adaptation B)This trait is a byproduct C)This trait is noise D)Impossible to say

B (Makes and models of cars have not been around long enough for natural selection to have built adaptations specifically for recognizing them. This ability is most likely made possible using other adaptations (e.g. those for object categorization, explicit memory, language).)

Today many people have extreme phobias of snakes and spiders (which very few people die from), while nobody (or very few people) have a phobia of electric outlets and cars (which do kill lots of people). What does this imply? A)Our fear system is not an adaptation because it leads to negative consequences in modern environments. B)Our fear system is an adaptation, but it was designed in a world where snakes and spiders (not outlets and cars) were hazardous. C)Our fear system is well calibrated to modern environments D)There is no experience that can modify the activity of the fear system

B (Remember that adaptations are designed to solve selection pressures in the past.)

Think about the trait of having 10 fingers. Some people have been in accidents and lost some of their fingers. But, other than that, most people have 10 fingers. Given this: A)The heritability of having 10 fingers is close to 1 B)The heritability of having 10 fingers is close to .5 C)The heritability of having 10 fingers is close to 0 D)None of the above. You can't infer anything about heritability from the above information

C

Which of the following is an example of a replicator (something that through its interaction with its environment reliably creates self-copies)? A) A species B) An individual (from a sexual species) C) A gene D) A family E) All of the above

C

New and colleagues proposed that human nature contains a mechanism in spatial cognition designed for the navigational challenges of gathering. They found that women had better spatial memory for the locations of 'fruiting trees' than men. Critics have argued that this sex difference is not due to ancestral selection pressures, but instead due to the way men and women are socialized in modern cultures. Which piece of evidence helps refute this criticism? A)Women had better spatial memory for more categories than merely 'fruiting trees' B)There was no sex difference in location memory for gender-neutral categories, like buildings C)There was no sex difference in location memory for female-gendered categories, like jewelry D)All of the above help refute this criticism E)None of the above help refute this criticism

C (On the theory that spatial memory is a function of the way men and women were socialized, a prediction would be that women would show a memory advantage for items women but not men have been socialized to value, like jewelry. If we find that there is no female advantage for such items, this would be evidence against the theory)

Which of the following is not evidence that a mechanism is an adaptation? A)The mechanism is specialized, complex and coordinated B)The mechanism is efficient C)The mechanism maximizes fitness in the modern environment D)The mechanism economically solves a specific problem

C (Remember that mechanisms are designed for the EEA, and not guaranteed to maximize fitness in the modern environment.)

Differences in height

Could be frequency-dependent, noise, or facultatively calibrated

Human children are different than human adults on many traits? What are some of the reasons for this? Discuss.

Critical to understanding differences in human children and adult traits is the idea that tradeoff parameters shift over a human's lifespan. Three important parameters are survival, labor, and reproduction. Over a human's lifespan, to take one example, it makes the most sense to invest in reproduction after a delayed period, and invest less after a critical age. At early stages, humans are still developing other features critical to their survival, and in later stages, specifically, after the point where returns from offspring>returns from self, it makes more sense to invest resources in the survival/reproduction of offspring. - *Some traits develop at a particular life stage precisely because that is the stage at which the adaptive problem the trait is designed to solve is present (not earlier, not later).

How many chromosomes are in a typically developing person's somatic cells A) 2 B) 23 C) 36 D) 46 E) 56

D

Suppose Dr. Joe finds that people in different cultures act differently when put in the same situation, for example that people in some cultures tend to be more generous than people in other cultures. That is, there is no fixed level of trust or generosity that is common everywhere. What does this imply? A)That adaptations for generosity are not universal in our species B)That there are no adaptations for generosity in our species C)That there is no genetic component of generosity in our species D)All of the above E)None of the above

D (A, B, and C (and therefore D) are all consistent with Dr. Joe's findings, but not one of them is implied by his findings. Remember the jukebox example from class. It is possible to get individual differences in behavior even with the same underlying psychology. If a universal adaptation takes in input from the environment on which it conditions which of a set of programs to run, we will observe differences in behavior even though the same set of programs are universal.)

Optimal foraging theory argues adaptations should spread to the extent that they optimize return (energy intake) per handling cost (energy expenditure). What does this predict? A)Holding handling costs constant, animals will choose a food that is higher (vs lower) in calories B)Holding calories constant, animals will choose a food that is easier (vs harder) to acquire C)Animals will choose a food that yields 5 calories per 1 calorie burned in handling over a food that yields 10 calories for every 5 calories burned in handling D)All of the above are correct predictions

D (According to optimal foraging theory, all other things being equal, animals will choose food that has more calories, which is easier to acquire, and which give the most "bang for the buck".)

Silverman & Eals proposed a "Hunter gatherer hypothesis" of sex differences in spatial cognition, and found that women remember more locations of objects in arrays of other objects than men, but that the category of the objects doesn't really matter in this task. New and colleagues proposed a "Gathering navigation theory" of sex differences in spatial cognition, and found that women outperform men at real world orientation when the target of orientation is a gatherable food. What do these findings imply? A)All spatial adaptations for gathering operate only for gatherable foods B)All spatial adaptations for gathering operate on a wide class of non-gatherable objects C)There are no spatial adaptations for gathering, these findings are contradictory D)There are at least two spatial adaptations for gathering

D (Although both theories propose adaptations for foraging, each one proposes an adaptation that solves a different part of the problem of foraging. One for orienting toward gatherable foods and one for remembering the location of objects in an array.)

Suppose Dr. Josh has a theory that a particular region of the brain is adapted for detecting spiders. Spiders have long been a hazard in human ancestral environments, and by detecting and avoiding spiders this hazard could be mitigated. Now suppose that Dr. Isabelle finds that this same region of the brain responds to lots of different kinds of stimuli besides just spiders, including asterisks and other non-spider shapes that have a central mass and ~8 radiating lines. What does this imply? A)The brain region in question is not an adaptation for detecting spiders B)The brain region in question is not domain specific C)Both A & B D)None of the above

D (Remember the distinction between the proper domain and the actual domain. It is possible that what Dr. Isabelle has found are the specific features of spiders that the domain specific mechanism takes as input (after all having a central mass and ~8 radiating lines are the perceptual features spiders share with one another). Because asterisks possess these features, they may fall into the actual domain of the mechanism. Dr. Isabelle's findings leave open the possibility that the brain region is an adaptation for detecting spiders and that brain region is domain specific.)

Suppose an anthropologist discovers a hunter-gatherer group where the women hunt and the men gather. What does this imply? A)That the sexual division of foraging labor in humans is a purely social construct B)That there was no reliable sexual division of foraging labor in ancestral environments C)That adaptations for hunting or gathering should not be sexually dimorphic D) None of the above

D (Remember to think about the average case, where the vast majority of cases show the opposite pattern.)

Differences in extroverted personality

Either facultatively calibrated or configured

Think about the Hawk/Dove game from the description in class. What do you think the conditions are when there will be an internal/mixed equilibrium of hawks and doves (e.g., what relative value of cost and benefit)? What conditions should make Hawks go to fixation? What conditions should make doves go to fixation? Explain your predictions:

Equilibrium: c=2b Hawks to fixation: b>c/2 Doves to fixation: c/2>b -

True or False: All organisms are sexually reproducing

False

True or False: An explanation at the computational level of analysis is all you need to fully understand a mechanism.

False

True or False: The evolution of sexual reproduction first requires the evolution of two distinct sexes

False

True or false: Every time a mutation occurs that cause an increase in reproductive rate, it will reach fixation.

False

True or false: Natural selection only results in organisms that are selfish

False

True or false: If a gene is common in a gene pool because it solves a particular adaptive problem, that means it always solved that adaptive problem and never solved a different adaptive problem.

False (A single gene can have effects on many aspects of the phenotype (i.e. pleiotropic effects), contributing to the solution of a number of adaptive problems. A gene can also serve different functions across time, for example in the case of serial adaptation.)

True or False: It is impossible to test between a theory that a trait is an adaptation and another theory that the trait is a byproduct of another adaptation.

False (Adaptations have design features tailored to the specific adaptive problem they were designed to solve. )

True or False: If a man reproduces, every gene in him has a chance to be passed down to his offspring

False (Don't forget about mitochondrial DNA! It is only passed on by mothers.)

True or False: The only reason children have different traits than adults is because it takes time to build a fully adult phenotype.

False (Remember developmental stages are targets of natural selection. This question implies that there is something privileged about adulthood and that development is just a way of getting to adulthood.)

True or False: Saying a trait is 'learned' is the opposite of saying that a trait is 'innate'.

False (Remember that learning mechanisms can be innate, for example, the mechanisms that allow us to learn language.)

True or false: If a mechanism operates on more than one kind of thing (e.g., both food and mates), then it is not domain specific.

False (Remember the proper domain/actual domain distinction! A mechanism for processing faces might operate on face-like things just like a mechanism for processing coins might operate on washers (coin-like things).)

True or False: If a trait X emerges earlier in development than trait Y, that means that trait X is a simpler trait to construct than trait Y

False (Remember the vasculature example in class. These are early emerging adaptations, but are quite complexly organized. When thinking about timing, don't think about a progression from simple to complex, but rather step by step building process that is functionally organized at each step along the way.)

True or False: If there is a reliable sex difference in a skill like spatial memory, that means that nothing can be done to make a person's spatial memory better or worse.

False (Sex differences don't imply anything about how fixed/malleable a trait is.)

True or False: The EEA (Environment of Evolutionary Adaptation) is the same for every adaptation.

False (The EEA is a statistical composite of features of the environment that acted to shape an adaptation. The EEA for one adaptation may overlap with that of another, but it may be entirely different. Refer to Lecture 9.)

True or false: Evolutionary psychology predicts that behaviors will be universal

False (The same underlying psychology can give rise to individual differences in behavior.)

True or False: Fear of heights is not innate in humans because newborns are unafraid of heights and only develop this fear once they have experience self-locomoting.

False Innate does not imply that experience is not required for a trait to develop.

True or False: Saying a trait is innate implies that it doesn't require input from the environment to develop.

False Remember that all adaptations require input of one kind or another from the environment.

True or false: The phenotypic differences between human males and females are due to women and men having many different genes*

False ! Remember: 22/23 chromosomes are the same in men and women, and both also have at least one X chromosome. Only the tiny y chromosome differs. The effect of the Y chromosome is to trigger a masculinization program that is encoded in the genes of both sexes.

True or false: For a gene to spread to fixation the strength of selection must be very strong*

False ! Selection can be strong or weak, the strength just means genes are more likely to reach fixation more quickly or more reliably (given the random forces).

If there was a sudden change in the environment after a long period of stability, what would you predict would happen to heritability of a given trait?

For most of the traits that we would calculate heritability for, we would expect that a sudden change in the environment would increase heritability. This is because if the trait in question is an adaptation, natural selection is "eating up" the variation over time (e.g., bad mutations get selected out). Neutral variations (genetic variants that produce no effect in that environment) are not selected against and can thus accumulate. But, if the environment changed, it is likely that at least some of these once neutral variations will no longer be neutral, increasing the variance in the trait due to genes, meaning that the heritability of the trait would increase. (One exception to this general expectation is the case when the old environment imposed frequency dependent selection (thus, variability due to genes) and the new environment imposes directional selection (thus eliminating the variability due to genes as the favored variant goes to fixation).

In twin studies, the concordance rate is used to help estimate heritability. Concordance rate is defined as the proportion of cases that are concordant out of all possible cases. Concordance means both members of a pair share the characteristic. So, if Paul and Jeff are twins and they both have brown hair, they are concordant for hair color. If only Paul is blonde, they are discordant for hair color. Identical (or monozygotic) twins share ~100% of their genes, while fraternal (or dizygotic) twins share ~50%. - What does it imply if the concordance rate is higher among MZ than DZ twins?

If the concordance rate is higher among MZ than DZ twins, MZ twins have a higher probability of sharing a given phenotypic trait than do DZ twins. Hence, in terms of heritability, we would infer that the heritability is higher than zero (some amount of the trait difference between people is attributable to their differing genes).

What does it imply if the concordance rate is the same for MZ and DZ twins?

If the concordance rates are the same for MZ and DZ twins, MZ twins have the same probability of sharing a given phenotypic as DZ twins. Hence, we would infer that the heritability of the trait in question is 0 (that the differences between people on this particular trait are unlikely to be caused by differences between genes).

Think of a phenomenon you might want to model the natural selection of. Describe it.

In a population I am studying, there has been increase in the # of BRCA1 mutations over time. I am interested in understanding why the BRCA1 mutation rate has increased over time, especially given my understanding that it is some kind of tumor suppression gene.

Imagine that in the ancestral past some people ended up in safe environments and some people ended up in dangerous environments. Imagine further that there were cues present in the child's environment that reliably predicted what kind of environment they would end up in as an adult. Knowing this and only this, what would Life History Theory predict about how a mechanism in children today should use this information?

In contrast to question 3, the mechanism SHOULD be designed to use this information.

Suppose you learn that height is 80% heritable. Does this mean that height is 80% caused by genetics? Why or why not?

No, heritability is not the same as being "caused by genetics" (genetic basis). In this case, the fact that height is 80% heritable indicates instead that height's variation (as a phenotypic trait) within a certain population that is due to genetic variation (between individuals in that population).

In the example used in class, the 'petri dish' imposed a limit on population size. What do you think would happen if there was no limit to population size? Would natural selection still work? Explain.

There would likely be other constraints on the # of bacteria alive (ie due to competition for food between bacterium). Because of this, and as long as there is still nonrandom change in replicator frequency of bacteria genes (allowing for variance), natural selection would still work.

Consider two developmental milestones, like learning to walk and speaking in complete sentences. What would it imply if one of these milestones reliably occurred earlier in development than the other? Discuss.

They may both be "targeted by mechanisms of facultative adjustment" - in other words, they may both be appropriate for or needed/helpful(together where their confluence could define a certain stage or together as part of larger change) in enacting strategies to promote a human's developmental goals at a certain point in her/his life. Key thing it does NOT imply: that the trait/behavior/capacity is "easier."

True or false: A gene could end up at fixation merely by random drift

True

True or false: Autosomes are equally likely to be passed on to daughters as they are to sons

True

True or false: Studying the nature of modern humans can help inform our understanding of the ancestral world.

True

True or False: Studying details of hunter-gatherer life can give us clues as to the kinds of mechanisms we should expect in human nature.

True (Insofar as modern hunter gatherer life reflects the persistent problems of ancestral hunter gatherer life, studying it can give us information about the adaptive problems faced by our species through evolutionary time.)

True or false: Evolutionary psychology predicts that psychological adaptations will be universal

True (Psychological adaptations do not imply that the behaviors they produce will be universal, but they do imply that the adaptations themselves will be universal.)

True or false: There is a tighter fit between the solution to an adaptive problem and an adaptation's proper domain than to its actual domain

True (The particular solution to the adaptive problem owes its design features to the proper domain. That is, the proper domain of the adaptation is what the adaptation was "made for" so the solution will reflect that function and more tightly fit the proper domain than the actual domain.)

Can you test between an 'adaptation' theory and a 'byproduct' theory for a given trait? How?

Yes, you can use design evidence to test between alternative theories of both adaptation & byproduct theories -For example, you can see if an adaptation is not well explained as a byproduct of something else - Byproduct theories are second-order adaptationist theories because byproducts are byproducts of adaptations. The byproduct theory thus implies design features for the adaptation the byproduct is a byproduct of, and that the byproduct trait/function is not one of these features. These predictions can then be tested against the predictions of the alternative adaptation theory.

Consider the human hand. Pick one trait or function that is an adaptation and one that is a byproduct, and explain.

__

What is represented by V_E?

amount of variation due to environmental factors

Heritability is typically defined as LaTeX: H=\frac{V_G}{V_G+V_E+V_{GxE}} H = V G V G + V E + V G x E . What is represented by V_G?

amount of variation due to genes

What is represented by V_GxE

amount of variation due to that of genes x that of environment

What kind of tools could you use to build a model natural selection?

bacterium in a dish, sugar, UV rays (observe population, count populations of mutants/competitors over time)

Consider the object ... Suppose Barry has a theory that this object is a tool for etching lines in clay. Suppose Larry has a theory that this object is a tool for smashing meat to make it tender. How could you arbitrate between these theories using design evidence?

can use predictions to test hypotheses! FOR EXAMPLE: Barry's theory predicts (re: coordinated features of tool): -bumps on tool etch lines in clay effectively -tool able to be maneuvered in a way which allows for ^ easily Larry's theory predicts (^): -tool operated from long end and able to make pounding motion -bumps on tool effectively tenderize meat DEPENDING ON WHICH SEEM MORE CONVINCING & ideally, you will look for predictive reasons in the following categories: Specialized, complex, coordinated features Reliably solves adaptive problem Efficiently solves that problem (and not others) Economically solves that problem Unlikely to be a byproduct of something else

Considering one tool or type of model, what would go into a model of your phenomenon? What are the important parts?

model observing # of mutants in given population, see that mutation marginally increased reproductive rate/resulted in mutation spreading to fixation mutation does this by randomly changing gene (replicator) form - and when done in a way which causes replicator reproduction better than alternatives, will allow for replicator to reach fixation

In class we discussed 4 ways individual differences are expected to result from natural selection: facultatively calibrated adaptations like anger proneness; configured adaptations like language; frequency dependent selection like blood type; and noise like mutation-selection balance. What do you think is the most likely explanation (and why) for the following individual differences: - Differences in intelligence

most likely noise