Human Evolution and Behavior

Problems with Memetics

1. Can't define boundaries of meme (but also hard to define boundaries of gene or species) 2. memes merge together (but genes do this too- introgression, horizontal transfer by viruses/plasmids, etc) 3. Only somewhat valid if culture looks like genetics-- but it doesn't

Bias in cultural transmission

1. Direct bias- given choice between 2+ alternatives, a genetic predisposition or prior knowledge may favor certain types of info being adopted (Brussel sprouts vs. chocolate cake) 2. Indirect bias- cues about one trait e.g. wealth, sporthing prowess-- bias observation of an unrelated trait (clothes, fashion, politics) (bank logo on sports jacket, no correlation but people go for it) 3. frequency dependent bias- - commonness/rarity of trait affects probability of transmission - e.g. conformity (predisposition to adopt behavior of majority) - when NS favors resilience on social learning, conformity also favored

Key concepts of evolutionary pyschology

1. Evolved psychological mechanisms (mental adaptations, context-specific emotions, preferences) Juke box model- idea that moduels have different programs that they can play out depending on differnet sorts of environmental input Ex: jealousy = adaptation to keep your partner 2. Environment of evolutionary adaptedness (EEA) - we might not be adapted to environment we are in now, but in the environment from before - John Bowly- infants separated by parents (clinging to parents = successful strategy to ensure that they don't leave you alone and you survive) 3. Domain specificity (massive modularity) - human psychology dominated by specific modules with particular evolved functions, not general processes

Case for Domain specificity

1. general solutions fail to guide organism to correct adaptive solutions 2. even if they do work, general solutions lead to too many errors and are thus costly to the organism 3. what constitutes a 'successful solution' differs from problem to problem

Australopithecus afarenis "Lucy"

3.2 mya Bipedal- evidence by structured knees, hips and hip joins and lumbar curve Small brain volume (suggests that bipedalism evolved before large brain size in hominins)

Early hominins

7 mya; similar to modern apes in behavior and appearance, but they walked upright Why? Climate change, transition from forest to grassland, expansion into new niche

Flawed logic of sociobiology

Adaptationism- assumes that behavior must have some adaptive value (red swellings- no adaptive value?)

Adaptive behavior vs. Adaptation

Adaptive behavior --> functional behavior that increments reproductive success - quick fix - Fish- use feather/piece of bread as lure to catch prey (short term effect) Adaptation --> character favored by natural selection for its effectiveness in a particular role - long term solution - Anglo fish- glow/luminescence -- allows them to catch prey

Who studies HBE?

Anthropologists doing behavioral ecology - small communities in remote regions - often hunter-gatherer/ traditional pastoralists - directly observe their behavior In recent years there has been increasing use of historical records - Europe - N. America - S. Asia

Evolutionary Psychologists

Argue that researchers should investigate the psychological mechanisms that underlie behavior patterns Argue that adaptations guiding human behavior are found at the level of pychological mechanisms Human behavior is unlikely to be adaptive much of the time 'adaptive lag hypothesis'

Human Sperm Competition

Baker and Belllis- suggested sperm competition has played improtant role in evolution of human mating strategies 'Men's relatively large testes provide one solid piece of evidence that women in human evolutionary history sometimes had sex with more than one man within time span of few days' Testes mass increases as body mass increases Testes size was bigger in males in which females had multiple partners Idea doesn't hold up well- wasn't prevalent enough to drive increase in testes size

Rise of behaviorism

Combination of theory and methodology Concerned with measurable, quantifiable aspects of behavior, rather than inferring unobservable events

Comparative Psychology Vs. Ethology

Comparative - Few model species; controlled lab conditions, behavioral generalities (universal laws, relevance to human behavior) , learning and behavior Ethology- many species, natural beahvior in wild, differences in behavior (basis in evolution, diversity), innate/instinctive behaviors

Summary of HBE

- BE proved useful in understanding non-human animal behavior - HBE arguably less successful - EP's have been critical of HBE's ~Adaptive behaviors vs. adaptations ~ psychological mech. focus of selection ~ Adaptive lag and past selective environment

Human behavior is highly flexible

- Behavioral flexibility allows us to behave in an adaptive manner in all kinds of environments - HBEs emphasize "adaptability" of human beings rather than our adaptations - Universals of 'human nature' are emphasized to a lesser degree than other approaches (behavior more shaped by local adaptations) - this need not imply conscious attempts to behave adaptively or maximize reproductive success - humans alter their behavior flexibly in response to environmental conditions in a manner that optimizes their lifetime reproductive success - selection favors the tendency to respond to new environments by optimally trading off costs and benefits of strategies - human behavioral ecologists are mechanism neutral with response to the proximate causes of how this occurs

In defense of HBE

- Behaviors can be observe directly, while psychological mechanisms are usually inferred - Knowing how selection operates in the present may inform our understanding of what happened in the past - Rigorous hypotheses can be formulated and tested

Dairy Farming and Lactose Absorption

- Coevolution of dairy farming and genes for processing milk = good example for gene-culture co-evolution - Human adults require enzyme lactase to break down protein lactose in cow's milk - whether or not an adult can digest lactose is largely down to whether he/she possess appropriate copy of specific genes - population who have highest gene frequency and tolerance is highest in cultures that practice dairy farming - populations who don't have culture of dairy farming and pasteurization have less tolerance and low gene frequency

Types of cultural selection

- Cultural evolutionists are interested in process that underpin cultural change - Describe route by which cultural info passes among individuals (mode of transmission)

Genes and culture sometimes co-evolve

- Culture contributes to selective environment - Genes determine response - Use mathematical techniques, to model the transmission of genes from one generation to the next, while also incorporating cultural traits into their analyses - Human sociobiology --> gene culture coevolution Lumsden and Wilson - Elements of culture, 'culturgens' are transmitted between individuals - human brains are programmed by genes to have rules that make them more likely to acquire adaptive, than non adaptive, culturgens ^^ criticized

Is brain too complex to have undergone recent selection?

- Evolutionary psychologists have argued that minds are co-adapted gene complexes that are unable to respond quickly to selection - but numerous genes involved in functioning of nervous system and brain exhibit statistically significant signs of recent selection - such genes include those expressed in: 5HT transporter Glu and glycine receptors olfactory receptors synapse associated proteins energy metabolism

Marriage Practices

- Monogamy - Polygyny - one male several females - Polyandry - one female several males - while resources are critical to breeding success of females but can be monopolized by males, behavioral ecologists predict polygyny - may pay a female to choose partner who already has a wife if he has more than double the resources of a bachelor - females may raise more children by marrying a married male with higher quality resources than an unmarried male with lower quality territory

Critiques from Evolutionary Psychologists

- Researchers should investigate the psychological mechanisms that underlie behavioral patterns - Adaptations guiding human behavior are found at level of psychological mechanisms - human behavior is unlikely to be adaptive much of the time - human behavior in contemporary populations might only rarely be adaptive as we are living in environments that are drastically different from those inhabited by our ancestors

Parent-offspring conflict: Conflict in the womb?

David Haig applied Triver's parent offspring conflict idea to human pregnancy Influenced by observations of genomic imprinting in mice Genomic imprinting occurs where genes are expressed in a parent-of-origin specific manner In mice, genes imprinted by males produced fetal growth factor and other genes imprinted by females produce mechanism for destroying that growth factor Womb may be battle ground in which genes play out their interests at the expense of our health

Cultural Evolution: Memes

Dawkin argued that memes have qualities required of replicators 1. longevity = lifespan 2. Fecundity = number of descendants 3. fidelity = accuracy of replication meme= unit of culture/imitation

Genus Homo

Members evolved larger brains, manufactured stone tools, and relied more on meat

Dissenting voices of Sociobiology

Methods flawed, assumptions naive Reductionist and biologically deterministic (do society at large and individual behavior really reflect on biological imperatives?) Disturbingly close to pseudo-evolutionary arguments used in recent past to justify inequality, discrimination, eugenics, colonialism, and genocide

Denisova hominins

Mitochondrial DNA analysis gave estimated divergence time from Neanderthals and modern humans of 1 mya More diversity between 2 individual found the same cave than seen in all of European neanderthal remains

Modern human populations

More elaborate and standarized tool kit (blades, chisels, etc) Tools made from antler, ivory, bone Raw materials transported over long distances Construction of elaborate shelters Creation of art and ornaments, ritualized burials

Nature vs. Nurture Def

Natural selection (nature) upon the brain plays a role in determining what we are capable of learning Experience (nurture) effects development of brain and our capacity to learn both important

Nature-Nuture Duckling Example

Newly hatched duckling's prefernece for their maternal calls of their own species are affected by hearing their own vocalizations in the egg Present at birth but not unlearned (exposed to sound)

Problems with Juke Box

No uniform human genetic program Environmental inputs build the mind Pragmatic issues increase genome size (not sure about this one) New lessons from AI

Kin Selection: Hamilton's Rule

One individual (the actor) performs a behavior that affects another individual (the receiver). This behavior will be favored by selection if the reproductive cost to the actor is less than the product of the genetic relatedness of the recipient to the actor multiplied by the reproductive benefit to the recipient. Relatedness (shared genes) between individual and its sibling/parent = 0.5

How does altruism evolve?

One shot interaction-- we tend to interact with people more than once Best comprimise outcome: both get 2 years-- you and partner keep silent Requires cooperation- if you cooperate with your accomplice, and they dont get you full sentence

Evaluating EEA

Our species spent over 99% of its evolutionary history as hunter-gatherers (Undisciplined speculation and story telling, variability in time and space) EEA doesn't refer to a single place/habitat, or even a time period. It is a statistical composite of the adaptation relevant properties of ancestral environments encountered by members of ancestral populations, weighted by their frequency and fitness consequences.

Battle of the sexes

Parental investment --- Evolutionary stable strategies Male-female conflict over parental investment (eggs are more costly than sperm, basic asymmetry between sexes) Both parents may want offspring ^ females may be trapped into having made more investment in the child from the start Is there an advantage to investing less than their fair share of time and resources in the child?

Battle of the sexes (Dawkins model Results)

Payoffs are asymmetric: the male does well, the female does not Philander males do well In population with many philanderers, fast females do poorly Selection may favor philandering in males and coyness in females Philanderer males and coy females unlikely to breed ^Neither pays the cost of wasted courtship, but no benefit of reproduction either Outcome: dynamic state of philandering and faithful males, and coy and fast females Dawkins model: 5/6 females are coy and 5/8 males are philanderers Males more likely to defect and not pull their weight in parental investment -- more likely to be unfaithful?

Horizontal Tranmission

Peers, people you're in school with, friends

Overall evaluating EP approach

Problems with EEA Lack of integration of evolutionary biology Problems with juke box model (lack of) universality of sex differences

Key points of sociobiology debate

Reductionism and determinism -- all of sociobiologists major protagonists have stated that they do not believe in genetic determinism. Complex traits: 'a gene for' language? Prejudice -- sociobiology is vulnerable to prejudicial interpretations Story telling- naive assumptions about adaptive value, little info about early selection environments of constraints of phylogeny culture concept- transmitted culture, and gene-culture co-evolution ignored

Where does sociobiology stand today?

Rejected by social sciences. Negative connotations Non-human behavioral ecology emerged -- revolutionized understanding of animal behavior as a product of evolutionary history and adaptation to the social and physical environment

Behavioral Ecology

Revolutionized the understanding of animal behavior as product of evolutionary history and adaptation to social and physical environment Topics: Genes- eye- view Kin selection Parent-offspring conflict Reciprocal altruism Optimality Models Evolutionary Game theory

Reciprocal altruism

Robert Trivers -- altruistic behavior among unrelated individuals could be selected for if there was a high probability that it would be reciprocated, and individuals remember previous interactions to prevent cheating Ex: blood sharing in vampire bats (regurgitate blood if other vampire is starving) -- more likely to feed other ones that have fed them (evidence of sharing but no evidence of withholding blood if someone doesn't give it to you) Ex: predator inspection of small fishes Trivers argued that reciprocal altruism is likely to have evolved in small stable social groups inhabited by our ancestors. But how?

Parent-offspring conflict

Robert Trivers --> parents should favor equal investment in all their offspring while offspring should favor increased investment in themselves Offspring should try to get as much food and support as possible from their parents before becoming self-sufficient (i.e. psychological manipulation) This leads to parent-offspring conflict over the amount of investment infant receives

H. Neanderthalensis

Robust, heavily muscled with thick bones, and slightly shorter than Homo Sapiens Large brain volumes- typically larger than modern humans Co-occurred with modern humans Interbred with some populations of modern humans

Bipedalism favored by selection

Scan for predators, frees up hands

Kin Selection

Selection acts on genes Genes can increase in frequency (be selected for) if the individual that carries them behaves in a way that increases its own reproductive success Genes can also incraese in frequency if the inidivudal that carries them behaves in a way that increases reproductive success of others who carry those genes Close kin carry same genes Selection should favor behavior that enhances kin reproductive success

Darwin- humans have common characteristics with animals

Self preservation, sexual love, love of mother for new offspring, power possessed by the later for suckling Examples of learning and intelligence Even fear and emotions-- apes, monkeys, and humans have instinctive dread of serpents Terror- muscles tremble, heart palpitates, sphincters relaxed, hair to stand up

Menstrual cycle shifts

Strategic shift between preferring 'good dads' for long term contexts and 'good genes' in short term contexts at high conception risk? Lower testosterone males- less genetically fit and less competitive, but more willing to invest heavily in relationships and chidlren ^ this man to take care of baby, but at conception find someone with good genes

What is human sociobiology?

Study of social behavior in the context of natural selection Structure of animal societies, and the way and means by which animals find mate,s care for young, compete for resources are products of genetic evolution NS shapes way we interact with others

What are all cultural Darwinians fuss about?

Suppose there was color, and you don't know color. If i told you about color, either you would have adopted the viewpoint of color OR you would have constructed your own idea of color, which may be completely different from mine So either way, doesn't matter if I passed it on or you built it

Winning strategy for prisoner's dilemma

Tit-for tat --> cooperates on the first go, then simply does whatever its partner did the last time If it meets a co-operator, it cooperates and reaps the benefits if it meets a defeator, it defects and avoid being punished TFT = evolutionarily stable strategy

Evolutionary Game Theory

Way of thinking about evolution when the advantage of behaving in a particular manner depends on what others are doing Goal = work out what behavior constitutes most stable strategy

Sex differences in mate choice

Women want men with resources --> good financial prospects - women have to bear burden of internal fertilization, and 9 month pregnancy period, and would benefit from males with resources Men want sex But both lists about what men and women rank in each other are very similar (mutual attraction-love, dependable character, emotional stability and maturity, pleasing disposition)

Is there culture in other animals?

Yes- primates, nonprimates (whales, dolphins) Ex: monkeys performing game where monkey A will put finger in monkey B, biting it just hard enough that it can't take its finger out but not enough to bite finger - No function, so researchers determined this is way of assessing cultural/social bond Ex: Hump back whales - Whale will emerge and whack surface of water with tales - Impact of tail and water stuns the prey so whale can catch it and eat more - based on how often each whale is seen in proximity to other whales - this technique is socially transmitted - other whales (in a different site) less likely to see and adapt it - Doesn't appear to have genetic transmission, just observational

Evolutionary Game theory: Reciprocal Altruism and Prisoner's Dilemma

You are criminal. Hired to rob a bank, and partnered with another criminal who you don't know well. But you get arrested and placed in separate cells. Prosecutor makes deals: if you confess and accomplice remains silent, all charges will be dropped against you and you use your testimony to ensure your accomplice does 10 years Lifewise, if accompice confesses and you remain silent, then they will go free and you will have 10 years in jail If you both confess I get 2 convinctions, but you'll both get early parole (5 years) If you both remain silent, have to settle for token sentences on firearms possession charge (2 years) Solution: sell out your partner! -- you can never do worse than that. (if you stay quiet, you'll never do better)

Vertical transmission

any cultural transmission you inherit from parents (language, politics, religion)

'genes hold culture on a leash'

brain is adapted through Darwinian evolution to be response to particular types of culture but not to others - on some level, brain is able to process adaptive, nonadaptive, and maladaptive culture units and select them (less likely to engage in maladaptive ones) - yes we are susceptible to culture but it's still a darwinian, genetic process

Puzzle of human concealed ovulation

concealed ovulation forces man to maintain courtship to prevent cuckolding, which allowed selection for male parental care and resulted in females gaining investment for their infants concealed ovulation decrased attractiveness of other men's partners, reducing tension and strengthening male cooperation within groups concealed ovulation allowed women to mate with multiple partners, encouraging them all to supply food to infant or to refrain from injuring it

Increasing brain size (how)

consequences of bipedalism: descended larynx (brain case expansion, necessary for speech) Shortening of pelvis Decreased opportunity for development during gestation, young born at earlier developmental stage Skull plates not fused at birth, allows for significant brain growth following birth. Extended childhood, greater opp. for development

Gene culture co-evolution too reliant on theory

gene culture coevolution has not yet developed a strong tradition for empirical work but see applications to dairy farming, yam cultivation and sickle cell heterozygosity Difficult to run experiments on something that requires change over many generations

Gene's eye view

gene is selected on one basis only, its average effectiveness in producing individuals able to maximize gene's representation in the future generations

What came prior to sociobiology?

Ethology-- objective study of animal behavior in natural conditions Ethologists stressed species-specific behavior and often downplayed behavioral variability within populations

Neglect of recent developments in evolutionary biology

Evolution is a result of multiple processes Group and multi-level selection are now respectable Evolutionary change can be fast 21 processes that play a role in evolution (stressing that his classification was incomplete) 1. processes that generate variation (deletions, insertions, etc). 2. processes that restrict kinds of variation (gene conversion, self regulation) 3. processes that change frequency of variants (NS and sexual selection, genetic drift) 4. Processes that improve an organism's fit with its environment (adaptation by natural selection, exaptation) 5. processes that affect rate or direction of evolution (sex, mutation rate)

Primate sexual swellings

in many species of primates, females exhibit red 'sexual swellings' which are largest around time of ovulation In comparison, human females are described as having 'concealed ovulation'

Group Selection

individuals act for the good of their immediate group, or even for that of the species not evolutionarily stable strategy Rejection of group selection in favor of 'Gene's-eye view'

Human mate choice and character symmetry

male facial symmetry is more attractive- why? Male facial symmetry and female preferences for symmetrical faces must both exhibit 1. heritable genetic information 2. co-vary with fitness 3. sexually selected

A. robustus

prominent sagittal crest, probably associated with attachment of large muscles used in mastication

Oblique transmission

someone from your parent's generation that you copy or learn from for a different reason (school teacher, someone in power/prestige in your society)

Increasing brain size (why)

trend in hominin evolution Hardware developed as consequence of selection for greater memory and planning abilities. Maximize fitness in more complex physical and social environments, coordination of behavior (hunting) Motor skills- tool use development of language

Observation of hominid stone tool technologies

Example of how genetic evolution can be slow - Acheulian and Oldowan stone tool traditions remained very similar for hundreds of thousands even million years (flakes struck off pebbles, hand axes) - Slow cultural change: lithic technology - theoretical analyses have revealed that cultural transmission may change selection pressures to generate unusually fast genetic responses to selection in humans - entirely feasible that genetic and cultural evolution could sometimes operate at similar rates

Battle of the sexes (Dawkin's model)

Faithful males: will undergo extended courtship, and will help rear the young Philanderer males: not interested in courtship, will leave if they do not copulate immediately, will not help raise young Coy females: will not copulate until after long courtship Fast females: will copulate immediately

Homo Habilis

First hominin to show reduction in face and tooth size and some brain enlargement "handy man" - tools found - meat was important dietary component

Homo Sapiens and H. neanderthalensis

Genetic evidence of interbreeding H. sapiens population dispersed across europe and west Asia, carried 1-4% Neanderthal genes in their genome Humans share some nuclear DNA, but not mitochondrial DNA

Key concepts of Gene-culture Co evolution

Genetic evolution can be fast, cultural evolution can be slow. - Selection experiments and observations of natural selection in the wild have led to conclusion that biological evolution may be extremely fast Ex: gupplies-- life history evolution in just 11 years (substantial change in love history from body size to sexual maturation in just 20-30 generations) Ex: Kingsolver - review 63 studies that measured strength of selection in 62 species and 2500 estimates of selection - adoption of culture can lead to stable environment in which evolution can evolve - Substantial biological evolution can occur in thousands of years or less (Lake victoria- completely dry thousands of years ago) Rapid selection in humans - Human genome project Use statistical analyses of human genome Good evidence that our own species has undergone recent selection - Frequently these genes exhibit functions that imply the changes are responses to human cultural practices (agriculture, domestication of animals)

Nature-Nuture Chick Example

Gull chick will immediately peck at its parent's bill to initiate feeding, but with experience the accuracy of the pecking improves Present at birth but refined over time

Formal Models and hypothesis testing

HBE's use formal models to predict optimal behavioral strategies in specific environments Ex: optimal foraging theory

Optimal Foraging Theory

How should foragers search when in patchy environment? - Food provides energy - Searching costs time and energy - Time = energy too (selection favors strategies that maximize energy intake for the lowest cost during foraging, ultimately maximizing fitness)

Summary (lecture 2)

Human behavior is product of natural selection Nature vs. nurture = false dichotomy Evolutionary theory has been used and abused (by scientists and non-scientists) to justify a range of behavior, policies, and actions that today we find abhorrent

Associationism

Human mind at birth is like an empty box, free of inbuilt knowledge, gradually filled with experience

Social Darwinism

Idea that wealth/privilege are products of natural selection Biological evolution is progressive Competition should be encouraged Used to justify doctrines like social conservatism, militarism, eugenics, unfettered capitalism

Parallels between biological and cultural evolution

In Origin, Darwin discussed -Variation -in characteristics of individuals - competition- amongst individuals for survival/reproduction -inheritance- of characteristics to next generation Culture also exhibits these properties - variation- 7.7 million patents issued in USA - competition- 6800 languages, 10,000 types of religion - inheritance- religious and political attitudes strongly consistent between parent and offspring

Adaptive trade-off

Individuals are predicted to be selected to optimize how investment is allocated into different aspects of their life history Ex: Guppies- Females can invest in growing large or sexually maturing earlier When predation is high: - reach sexual maturity sooner, as smaller size - Have many smaller young Trade off having lots of big young because likelihood of predation is high When predation is low: - reach sexual maturity later, at larger body size - Delay having young sooner, invest in growth - larger fish are more fecund and have more and higher quality young - can afford to wait because likelihood of predation is lower Transplant experiment: When researchers moved high predation guppies to low predation sites, they switch their life histories accordingly Ex: Egg clutch sizes - birds produce eggs of various sizes - Large clutch size may result in parents being unable to feed all chicks, while small clutch size may result in missed opportunity to raise offspring - predicts distribution of eggs to be somewhere in middle

Autralopithecines

Large molars- enhanced ability to process coarse plant foods

Nature-Nuture: false dichotomy

Learning vs. Instinct Learning and experience are not everything (twin studies- some genetic control over intelligence, behaviors, addiction) Brain needs rules on how to learn. Spoken language is picked up autonmatically. Learning rules are a product of Natural selection Behaviors fixed by selection and inherited by ancestors

Cultural evolution in lab

Linear transmission chain- i tell you a story, you tell story to someone else, etc. etc. Can see how info changes along - have group of kids (in closed group), teach one of them X, and see how knowledge passes from one kid to another - how content evolves

Niche construction

- all organisms modify components of their environments - humans are unusually potent niche constructors - in humans niche construction is primarily based on culture (not immediate product of NS) - Clear evidence that cultural niche construction has modified selection pressures throughout human evolution - growing evidence of a genetic response to human cultural niche construction Ex: Deforestation- ecosystem change - agriculture and production of monoculture - water sources-access to water - people have spread from east africa all the way to north america (moved to different biomes than just grassland) - transition away from hunter gatherer societies - domestication of livestock - changes in desnities that we live in Ex: Sickle cell anemia, yam cultivation and selection for heterzygosity - Hereditary blood condition - cases misshaping of RBC - reduced oxygen carrying capacity, clogs capillaries - shortens life spans - more than 1 dominant allele, people who are heterozygous for the affected gene will have both normal and abnormal RBC - confers protection against malaria - malaria parasite cannot infect abnormal RBC - Kwa from West Africa cut clearnings in forests to grow crop yams - tree removal inadvertently increased standing water, which provided better breeding grounds for malaria-carrying mosquitoes - because, in heterozygous condition confers protection against malaria, this practice intensified natural selection of sickle cell allele - adjacent populations whose agricultural practices are different do now show same increase in allele freq-- supports the conclusion that cultural practices can drive genetic evolution - Malaria= more widespread after invention of farming - several genes seem to have been favored by selection b/c they provide resistance to it

Phylogenetic methods can be applied to langauges

- frequently used words evolve at slower rates - Infrequently used words evolve more rapidly - Ex: religion religion = cluster of memes says bible is successful because their affects are to change behavior of reader in order to pass it on - qualities of "ultimate religion" in order to spread - easy to get into, difficult to get out of - punish people for trying to leave Lots of children who can adopt religion People must convert others Challenging religion- treated severely

Key Concepts of HBE

- human behavior = highly flexible - flexibility allows for behaviors that will optimize fitness. these can be predicted using optimality models - Adaptive trade-offs exist: when one behavior comes at the cost of another, strategies that best balance the pros and cons of each will be followed

Case studies: inuit hunting parties

- inuit population (arctic Canada) has variety of animal species (fish, waterfowl, deer, seals, whale) Why do Inuit typically form groups of 5-16 to hunt beluga whales and groups 2-10 to hunt seals, but hunt ptarmigan alone? - hunts are cultural events? - hunters cannot easily exclude others from joining? - PREY SIZE ALONE = NOT ANSWER One predicition: OFT: optimal for what? - individuals will form group size that maximizes the average capture rate of prey per hunter For prey most effectively caught by single hunter (geese)- most common foraging group was 1. BUT when more than 1 individual was required to capture prey, common group size was not optimal (constraints due to social interactions/factors, can't say no to people)

Polygyny threshold model

- tested with study of marriage practices among Kipsigis of Kenya - over a certain threshold, the amount of resrouces monopolized by a mall will make him more attractive than a competitor with no other partners - in Kipsigis, women and children are dependent on money and land of men-- men have up to 12 wives - women choose to marry men who will provide most resources to her

Broad Aims of HBE

- to determine whether behavioral differences shown by contrasting human groups are responses to particular environments (look how ecological and social factors affect behavioral variability within and between pops) - to try to predict human behavior using optimality and fitness- maximization models

Drawback to HBE and Evo Psych

- what is currently adaptive may not have been adaptive in the past (and vice-versa) and may not be an adaptation - return to the adaptionist/just so story criticisms of sociobiology