Anthro 124A Lecture Notes
Anthro 124A Lecture Notes 124A
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Anthro 124A 12715 607 PM 15 15 Human Behavioral Ecology What is HBE Small segment of anthropology is growing and has increasing in uence Crosses over to cultural Anthro HBE our environment affects how we behave We shouldn t expect that all humans act the same under certain conditions Behavior is quite exible not all people will respond the same way Men vs women young vs old rich vs poor Behavior is contextdependent An adaptive behavior in one setting may not be adaptive in another setting Key Questions most important ideas in lecture How did the eld of HBE arise What are its guiding principles What kind of work do human behavioral ecologists do What kinds of questions do they ask How did HBE arise as a field of study Cultural ecology came out of the social sciences Looking at correlations doesn t have a theoretical basis to it Ethologyevolutionary ecology latter is theoretical Cultural Ecology There wasn t a good emphasis on why you would see something Emphasis on the importance of ecology on understanding social structure and social organization If you lived in a desert it would put pressure on you to live in a certain way but no emphasis on why that particular behavior might have been selected or valuable tness Key Research in Animal Behavior Konrad Lorenz studied instinctive behaviorsimprinting Tinbergen amp Lorenz Tinbergen Dutch ethnologistornithologist Lorenz Austrian zoologist omithologist and Both were leaders in thinking about animal behavior Tinbergen s Four Questions 0 PROXIMATE ULTIMATE how and why the behavior came to be Human behavior ecologists are more interested in ultimate questions We will focus most on 9 What is the survival value of the behavior adaptive function The difference is that proximate 9 WHAT and ultimate 9 WHY Ex Proximate amp Ultimate Causation Ultimate cause the ones that do have a better chance of surviving than the ones that don t it s about fitness Living amp reproducing are the 2 components of an organism Ex Human Fertility Patterns 0 Proximate Qualityquantity breastfeed longer causes you to have fewer children later on Ultimate Fewer births 9 higher child survival rates You can give birth to 15 children but you can t take care of them very well only 5 may survive Not always optimal to maximize All human behavior is not adaptive What is adaptive in one place may not be adaptive everywhere Strategies are conditional upon local environments Early Controversy The most controversial component was EO Wilson Talked about kin selection we should favor our relatives over nonrelatives animal communication pop biology etc One chapter talked about humans and applying the same principles to people Wilson s Claim There s a biological basis to all social human behavior Biology is primary culture amp environment are layered on top ALL social behavior is linked to biology He made some pretty strong claims Critic s Response Work got linked to genetic determinism Led to outcries about links to eugenics racism sexism etc Sahlins went to the other extreme said biology doesn t have anything to do with behavior Thinks of culture as autonomous from biology The False Dichotomy Behavior is in uenced either by biology or culture NO Biology and environmentculture interact behavior is a product of both Misinterpretation of sociobiology to set them apart HBE NOT Sociobiology and NOT cultural ecology Gets at the heart of the debate that they were rising again Basic Principles 3 main approaches to study human behavior 0 HBE Evolutionary psychology most popular Dual inheritance theory now called cultural evolution 0 Early on there was tension between these 3 as to which was the right idea Some tension still exists but there s been more collaboration now Temporal scale distinguishes the 3 groups to some extent Expected current adaptiveness HBE argues for the highest level There s been a lot of culture change People do things different from the past Principles of HBE Adaptation Adaptations are critical to tness Behaviors selected because they have bene ts to survival or reproduction Important to distinguish adaptation vs evolution Evolution can occur through multiple processes mutation drift gene ow ONLY natural selection can produce directional change and complex adaptive design linked to adaptation HypotheticoDeductive Research Strategy Human behavioral ecologists test hypotheses they are scientists in that sense Reductionist strategy Grandmother presence 9 higher grandchild survival Still take context into account How it works why it works Conditional Strategies Way of thinking about behavior Why you might see one thing in one place and not another The Phenotypic Gambit We know genetics underlies human behavior amp physiology We didn t have a good understanding of the specific genes linked to a trait Behavioral ecologists have blackboxed genetics said genetics is important but we don t care about how specific it is Looking at selective forces such as the environment rather than focusing on specific genes Plasticity amp Phenotypic Gambit We believe there was a lot of plasticity Allows us to change in response to changes in environmental conditions Ability to be plastic is an adaptation 1714 Lecture 1 continued Resource Acquisition You re going out hunting and there are 6 prey types which you can go after how do you make the decision to go after one and not the other Strategies differ according to sex age status etc Stereotypes about men hunting how universal are these stereotypes How does body size affect it Resource Transfers and Cooperation When do you share and when do you keep it for yourself And with whom When is it better to work together instead of alone Varies Short and longterm benefits of cooperation On the surface appears to be altruistic But sometimes it s an example of mutualism both parties are gaining benefit by working together Mating and Parenting Strategies As a species we provide a large amount of investment and time in our children Polygyny we ll look at the cost and benefits for men and women Life History Decisions Major life events that dictate our schedule of mortality Growing bigger maintaining the systems in our body reproducing If you re putting a unit of energy into one it can t be placed elsewhere 9 tradeoffs We ll talk about how that affects ancient anarchy Postmenopausal lifespan Women last very long time after they stop being able to reproduce This is odd to the animal world Lecture 2 Maj or methods behavioral ecologists use Naturally Occurring Behavior Primary thing behavioral ecologists do Distinguish them from other ecologists In the field look at what people are actually doing in their everyday lives instead of setting up a fake scenario to see how people respond NOT responses to hypothetical scenarios or behavioral lab experiments Focus on tracking behavior of numerous individuals Larger sample sizes Get broader information on a wider number of people Doesn t go as deep there are pros and cons Types of Studies Prospective Focal and scan sampling Go out and look forward in time Figure out what people are doing Eg In the upcoming season you ll see what they do with hunting Bring them into the study at time A then go forward and track reproduction anthropometrics Retrospective Looks back in time Sitting down with somebody and ask about their past pregnancies is the child still alive boy or girl is the child still alive etc Getting information about person s entire life history in one sitting Crosssectional At this exact point of time what s happening Census data going to see who s living in the community right now what s the sex ratio at this point in time Anthropometrics there s a drought and then you go and measure everything at that point Time Allocation Borrowed from animal behavior studies Focal follow Pick a single individual go and follow that person around for some set of time 20 min 12 hours Instantaneous scans Getting information on more than one individual at a time random moments Eg Walking around and if you re studying babies you will take notes on any babies that you see and what they re doing 0 You do this many times End up with a lot of data and then put that together to get a picture of what life is like Ethogram Inventory of behaviors or actions exhibited by an animal 0 Come up with a list of behaviors that is representative of what you want to track I Eg With babies cry fuss being bathed being bedded nursing etc I The numbers represent each individual I Do this across hours in the day and all days of the week Bene ts of Time Allocation A lot more reliable than retrospective accounts of behavior Allows us to record it as it s happening to get more accurate information Even if you re only looking at 13 households adds up to 100 individuals and if you do it over 134 days you can end up with 3495 observations Can study longer periods multiple seasons Larger sample sizes than with interviews Issues with Time Allocation VERY labor intensive Depending on how much time you have you can allocate different portions of the day 0 Scans easier than follows Coding can take additional time If you re going to do focal follows where you go into their houses you need to get the people used to the idea to you popping into their house 0 Took Dr Scelza 6 months to become comfortable with the family before she started her research with them Easier in some communities rather than others 0 May be strange if you do this in LA Dealing with Absence How do you record activities of those who weren t present at the time of the scan 0 If it was the person who was missing you can ask them what they were doing If it was a baby you can ask a third party such as their mother I Depends how reliable their memory is Third party may not reliably know about what they re doing Sampling bias 0 If you do sampling at an event you need to be aware there may be certain people you re less likely to capture I Loners may be underrepresented vs those who are more social I Private activities may be underreported eg Sex I Won t always have a COMPLETE picture Interviews Typically individual interviews Can yield both quantitative and qualitative data Quantitative 0 Marital amp reproductive histories o Recalltime diariessocial networks eg Partner freelists Scelza uses more structure and ends up with information being quanti ed Ask more detailed questions about their births Qualitative Who was present at the birth Where was the birth location Detailed data and context about an event Nuanced responses rather than yesno answers Focus Groups Done in the beginning of the study Get a group of people together 36 individuals less structured get ideas about what people think about a certain thing Build dialogue and response When you understand the context you can use this in the interview Issues with Interviews Recall bias Lower when talking about major events People don t tend to forget how many children they ve have but they may not disclose certain things Eg people may not tell the truth if they had a child who died You need to come back and ask the same questions over time and see if story remains consistent Subject sensitivity Infidelity is a hard subject to discuss May be safety reasons associated or they just don t want to tell you Same with number of seX partners 0 Some societies are open about this information others are not Census Data Residence Groups Can do it for households hunting parties Who is currently in the residence Name seX age Martu Group Composition Brought in groups contact was made out in the desert Living together in a group composition Aborigines Interview the people who are now in their 50s and 60s and ask who the people in the picture were and how they were related to that person Issues with Census Data Missing persons Some people tend to be away from home at a given time eg Migrant men 0 Men may be working outside home or community 0 Young men young educated men Group compositions might change seasonally family may split up seasonally Need recent history of ssionfusion to see how representative current composition is Classifying individuals Is the person a resident or visitor Sometimes is tricky in one area when wife gives birth she goes back to family and divorces the husband Visitor 9 resident Other types of Data Health measurements Anthropometrics Biomarkers stress hormone levels Paternity testing Ancestry studies Movement GPS tracking If they went hunting can see how far they went how many calories burned o ltemizations Food weights for portion sizes Household goods measures wealth Data Collection Fieldwork Smallscale societies Public domain databases Historical 0 Church registries can nd information on infant mortality in these data bases contemporary Data Analysis hypothesis testing predictions derived from evolutionary theory correlational data common eg Hunting success is positively associated with having more surviving children causal links rare be careful to see if authors are trying to imply a causal link or not Putting a child into fosterage leads to increased fertility later in life Signi cance and PValue is it actually an affect or just random chance Statistical signi cance Probability an effect is not likely due to chance alone Pvalue Want low pvalues less than 05 9 less than 5 chance that a result occurred by chance 0 The lower the better 9 greater signi cance If it s signi cant it means it is not caused by chance Signi cance and Meaning Just because something is statistically signi cant doesn t make it meaningful or important Eg If they say eating an apple a day decreases your chance from getting a heart attack by 01 then this is not important or a large enough amount of time to have someone change their behaviors o It has a very small effect 0 Additional to Pvalue you need to look at effect sizes 1915 Research position available transcribing 5 hours a week Joe Manson Jmansonanthrouclaedu The Problem with PValues Just because you have a value less than 05 it doesn t give you a concrete answer as to whether something has an effect Sample size matters bigger is better 0 If you have 10000 individuals in your sample and you found an effect you can be more certain that it s something real 0 Replication matters Con dence intervals reveals level of uncertainty in the result want it to be as narrow as possible Bayesian Methods look at effect sizes not Pvalue Tables amp Figures Pay attention to these in the articles that we read 0 Look at headings captions and labels 0 Look at the axis look at the scale Histogram Distribution of the frequency of data within a certain range bins Scatterplot Collection of points where one represents the value of one variable on X aXis and another on y aXis A Day in the Life of a Human Behavioral Ecologist Scelza worked with a group in Africa called the Himba They are pastoralists herding cows Most of their diet consists of sour milk and maize Only married men where a hat on their head Women have dreadlocks They make a majority of the things they use Herding the cow is typically men s work Goats and sheep children s work All the other work women How to nd out how old someone is The Himba have a name for each year or a year where something signi cant happened 12715 607 PM 112 15 Humans as Primates What is a primate Easiest way to distinguish apes and monkeys Apes don t have tails What is a Primate Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Primates 250350 distinct species General characteristics locomotion grasping hands and feet hind legs dominate opposable thumbs senses highly developed visual system less dependence on olfaction sense of smell Primate Life Histories certain characteristics that are typical among the primates primates tend to have altricial young most primate species are born and are helpless humans are categorized of secondary altricial young 0 opposite is to be precocious eg Horse when the baby is born and within minutes of birth can get up and walk around do a number of things on its own It can locomote it can see primates require intensive amount of maternal care strong bond singleton births few primate species where twinning is common 0 If you have one baby you can put a lot more investment in that one offspring I if you re carrying the baby around you are protecting them from predators slow growth and late maturation than other mammals gets accentuated in humans long lifespans high infant mortality low mortality during juvenile stage increasing during mid to latelife in woman menopause is found in very few species Primate Intelligence primates tend to be smart linked to the complex social networks that primates have spatial navigation kin recognition helpful to have an understanding of who the other members of your group are the interactions that individuals have had with each other distinguishing kin from nonkin toolmaking we don t see this too much in primates NeocorteX is particularly large for body size don t need to know the name just know it s a bigger brain Learning and problemsolving Social dilemmas of primates How to make due in large social groups hierarchies Kin recognition and kindirected altruism who am 1 related to in this group Mate choice inbreeding avoidance not a good idea to make with brother Linked to kin recognition to determine who brother is also related to social structure Primate sociality De nitions lmportant Social structure what the group looks like How many malesfemales Age structure If you did a census you would report back about this Social organization how the group behaves Hierarchies Dominancerank Bonding behaviors grooming Often nd primates in large groups Mating Rearing of offspring Defense easier if you have a larger group your individual risk goes down if you re in a bigger group 0 Resources 0 predators food sharingcooperation 0 food sharing is not very common among primates 0 we see in humans but not a lot in other primate species grooming is useful picks parasites off your body but also has an important social bonding as well Primate Group Types Mother amp offspring Altricial young Monogamous pairs Malefemaledependent offspring these species don t have very big groups Polyandrous groups One femalemultiple males offspring Polygynous groups think women go to gyn as a female One malemultiple breeding femalesoffspring More common than polyandry Bachelor groups Males usually subordinate until they can nd some females Sometimes sneak around Multimalemultifemale Multiple breeding males and multiple femalesoffspring Fissionfusion society Multiple malesmultiple femalesoffspring Similar to above group You have groups coming together and breaking apart Primate Group Types We see these group types mentioned above in humans Social Hierarchy Primate groups have strong dominance hierarchies Rank within seX Inheritance of rank tends to also occur within sex Whether inheritance occurs in females or males depends on which seX of groups remains in the same group Affiliative more cooperate and friendly Grooming Alarm calls Reconciliation Allocare reconciliation Agonistic more con ictdriven behaviors Territoriality patrols working together within the group but trying to keep others out who don t belong Threat gestures Competition for mates Infanticide warfare need to be able to distinguish these terms dispersal need to leave the group you were born into natal group 9 transfer immigration into new breeding emigrate into a new group Emigration movement out of a grouprange philopatry the behavior of remaining with one s natal group you reach maturity and either you stick around or you leave Primate Dispersal Patterns male dispersal more common than female dispersal know this not going to ask what baboons due in dispersal Why disperse Ultimate reasons for having one sex leave Inbreeding avoidance o It helps if your brothers and sons leave so you have more mating option Gets rid of the bad mating partners 0 Primary reason for dispersal Resource exploitation o Probably rare Intrasexual competition for mates 0 If you have an alphamale who s dominating mating then it may be useful for the other males to leave to go off and nd females to mate with Philopatry and Kin Support The philopatric sex the sex that sticks around forms close social bonds with kin Re ects wider patterns of kin selection Why favor kin Kin selection strategy where you favor your relatives even if that comes at some cost to yourself Giving something up you could have eaten yourself putting yourself at risk Inclusive tness related term which is a way to think about your tness in terms of not just your own success but the success of your relatives as well You share genes with the people you re related to If you re helping your kin you re helping pass on genes to the next generation Direct children you re having yourself Indirect genes that will be passed on with those you re related to Hamilton s Rule WD Hamilton 1964 You should have kin selection r is how related are you to the other individual what of your genes are you likely to share Think of the professor as an actor and we are the recipients She will defend you from a predator The bene t is the B and C is the cost to her for acting in that defense Could be injury energy expenditure of chasing away the predator rBgtC we are more related to some people than others looking at rvalues to see how closely related you are Kin Altruism if you think about Hamilton s rule it means you should make predictions on who you should help and when predict you would be more likely to protect someone that you re related to with r5 than r 125 help close kin more than distantly related kin Kin Recognition if you re going to favor kin you need to know who that kin is easier to detect maternal than paternal kin Difficulties recognizing paternal kin in most situations paternity is uncertain pairbonded species extrapair copulations onemale groups if other bachelor males are sneaking around in populations this can raise risk of paternity uncertainty multimale groups females mate with many males no longterm pair bonds Cues of Paternity proximity at time of conception male langurs protect infants from harassment only if present when infant conceived and had mated with mother dominance in mating alpha males have higher paternity chances Why recognize kin Avoid inbreeding Dispersal is thought to be an adaption to prevent inbreeding Primates have aversion to mating with close kin 0 Look at who they re making with o If there was random mating in the group the chances of having fatherdaughter progeny If it happens less than chance you can infer primates are able to distinguish their kin and avoid mating with them Kin recognition helps you cooperate Primate behavior summary Primate behavior is complex and multifaceted Many similarities to behaviors seen in humans 11414 The Human Anomaly Humans 0 Have colonized almost every terrestrial habitat on the planet 0 Have more complex technology 9 altering the planet 0 Exceptionally specialized and diverse What Chimps Can t Do Even when chimps are raised in human families they don t acquire language only vocabulary not rules of grammar Show little prosocial behavior Food sharing extremely limited among chimpanzees Even limited between mother and infant There is some food for sex trade but this doesn t occur very often Complex cooperation and task specialization are absent Two Fundamental Human Traits Hill et al proposes that there are two fundamental traits that set us apart Extensive reliance on social learning resulting in cumulative culture Extraordinary cooperation between nonkin including specialization and trade and complex alliance networks 0 If you have a lot of people out there you can interact with you can access what those people are doing and make deals with them 0 If you only deal with your kin you may not be exposed to different techniques 0 Allows us to have this ourishing of human culture Social Learning Hill de nes culture as information stored in brains institutions and material goods that is transmitted socially amp in uences behavior Culture allows you to move beyond what s in your brain or your body Being able to see what other people have created you have all these different options to look at Can greatly expand your ability to create something Units of culture change ideas trends in frequency over time culture evolves Eg Wearing skinny jeans today would have been strange many years ago Making parallels between genetic and human evolution Culture can be vertical or horizontal You can learn from lots of people not just down your lineage Other species have learned and regionally specif1c traditions but he doesn t label these as human culture Passed on by imitation The Ratchet Effect Cumulative cultural adaptation is unique to humans Ability to display complex behaviors built on prior socially transmitted information Looks at what you re doing and can imitate this this is step A Allows you to get to step B C D 0 Modifications and improvements are transferred faithfully until further changes ratchet things up again More than Imitation Some experiments done with chimps and then with kids to see the differences in how they learn There is an experiment where they made a box and there s a candy in the box Challenge is to get it out Experimenter shows them how to get it out they will do some unnecessary steps Chimps cut those steps out and get the candy out The kids repeated all the unnecessary steps There s some value in overimitating having that philosophy about learning allows you to learn more at the end Other Facets of Human Learning Teaching is common in humans rare in other species In humans for eg Little girl stirring pot wrong so her mom comes and with no verbal language puts her hands on top of the child s to help her stir it properly This is something seen in humans but not in other species Is a form of teaching Connected to other behaviors and emotions Humans have biases in the way they learn Kids overimitate with adults because they see the adults as prestigious gures and want to pay close attention to what they are doing Learning About Sociality Have to learn the norms and rules of a particular society in order to be a successful member of the society Eg Here you have to wear clothes but in Namibia it is acceptable to not wear as much clothes Rules themselves are not universal the fact that they ARE rules is what s universal Eg Controlled access to resources sexagespecif1c behaviors Those behaviors often reinforced through ritual and normviolators are often punished Ultrasociality Kin cooperation is common in many species but cooperation with nonkin is rare Economists predicted we should be selfinterested Given 100 there are two people and they tell you to split that 100 however way you want When you play this game with people around the world they always give something We have rules about how to behave that govern social interactions Reject unfair offers and punish those who make them even when these behaviors are costly to themselves Nonkin Cooperation We see doctors working with people in South Africa voluntary medical work Relief Efforts Donations to strangers Blood donation PreAdaptations What led to this suite of adaptations for ultasociality and social learning Intrinsic abilities Theory of mind the ability to understand the knowledge and beliefs of someone else Eg Sally places ball in yellow box She leaves and Ann moves it to the green box When children are really young they said the ball is in the green box When they are 4 they stay Sally will think it s in the yellow box but they themselves know it s in the green box 0 They differentiate between what they know and what Sally knows Chimps probably have some kind of theory of mind They have some knowledge about the beliefs of others Put a punch of tools in front of two chimps one chimp was trying to reach far to grab a tool but was struggling so the other chimp picked it up and gave it to him 0 This is why there s some debate of theory of mind 0 They won t get to the point that humans do though Bipedalism Allows for coverage of expansive geographical ranges Hunter gatherers daily home range 23 times that of chimpanzees Led to exposure to greater environmental variability o Leads to exposure for greater environmental variability Favors selection for social learning Manual Dexterity Bipedalism left hands free for other things Increase ability to use and make tools Social learning will help you to do this at a faster rate Preadaptations Shift in feeding niche Juveniles can t feed themselves you have to learn how to do it Will need to be provisioned by kin Bringing home large food packages led to sharing and exchange between kin and nonkin Cooperative Breeding Humans are cooperative breeders individuals other than the mother help to care for offspring Proposed this pattern was critical to development of prosocial norms and emotions in humans Hill will emphasis that men will supply food surpluses that can be shared with kin or nonkin Shared provisioning also allows for the care and treatment of sick of injured individuals Increase lifespan Cooperative breeding would also lead juveniles to think of others as cooperators not competitors Shows that caretakers teachers have their interests in mind Proposed Temporal Sequence Bipdedality led to manipulative dexterity amp larger home ranges Dietary shift more meat created juvenile dependence promoting cooperative breeding Cooperative breeding lmitative capacity and shared intentionality produce cultural capacity via teaching Cumulative cultural capacity led to language social norms extensive nonkin cooperation ethnicity etc 11615 LeviStrauss French anthropologist father of modern anthropology Structuralism search for underlying patterns in all forms of human activity Contended that core of kinship was marital exchange of women between groups 9 reciprocal exogamy o This was a cultural creation Reciprocal exogamy is a social arrangement in which groups are bound together through marital unions and kinship LeviStrauss amp Reciprocal Exogamy Men living in distinct groups need to ally with one another Reciprocity universal mental structure Acts of reciprocity create social partnerships Women are precious commodities of exchange Men exert control over kinswomen Marriage is means of exchange The atom of kinship rests upon four terms a brother his sister the sister s husband and their son Chapais and LeviStrauss Chapais takes this principle and situates it within our primate lineage Deep structure 9 Believes all human societies are built around same basic structure because all originated from same archetypal framework Deep structure Comparisons of human societies with primate relatives Comparisons of huntergatherer societies themselves Male PhilopatryFemale Dispersal 70 human societies practice male philopatry with majority of females leaving upon marriage Philopatry remaining in one s natal group upon maturity Dispersal leaving one s natal group upon maturity Why Disperse Prevents inbreeding Inbreeding can lead to homozygosity which is associated with an increase in risk of inheriting deleterious recessive traits Inbreeding and Incest Inbreeding offspring of two genetically related parents Biological Incest sexual intercourse between 2 individuals so closely related that their marriage is illegal or forbidden by custom Social Freud amp Incest Freud believed all humans are predisposed to be attracted to close relatives Social rules incest taboos necessary to prevent inbreeding Animal studies discredited this idea The Westermarck Effect People who live in close proximity for first years of their lives have reduced sexual attraction to one another as adults Argues AGAINST Freudian psychology Family members lust after one another necessitating incest taboos to prevent inbreeding Westermarck argues aversions toward kin with propinquity as a proxy are innate Incest taboos reinforce but don t cause inbreeding avoidance Primate Inbreeding Avoidance MotherSon Avoidance Chimps female dispersal Females alter behavioral patterns toward closely related males around estrus a recurring period of sexual receptivity and fertility in many female mammals Rare occurrence of motherson or sibling inbreeding Fatherdaughter avoidance Capuchins long tenure alpha males and male dispersal Fathers will be dominant when daughters mature Genotyping shows minimal fatherdaughter inbreeding Kin Recognition Male philopatry produces deep patrilines and shallow matrilines Kin recognition is key to fostering relationships Uterine kin more easily recognized motheroffspring maternal siblings Due to lasting nature of motheroffspring bond Patemalagnatic kin recognition unlikely in a promiscuous mating system Hypotheses about mechanisms of kin recognition in promiscuous systems Olfactory cues o Olfactory cues play an important role in the coordination of the mother infant bond Phenotypic matching Stable Breeding Bonds Enduring bond between a male amp female Encompasses both monogamy and polygyny More inclusive than pairbonding These bonds essential for paternal kin recognition Promiscuity 9 Polygyny 9 Monogamy First shift likely from promiscuity 9 generalized polygyny Multiple Polygynous harems in same group Subdivide into Polygynous units when resources are scarce Second shift from generalized polygyny 9 generalized monogamy Chapais supposes tools equalized males most couldn t keep control of more than one female amp generalized monogamy developed Fathers and Their Kin Once males can recognize their children recognizable kin groups become larger Individual can now recognize parents grandparents full amp half sibs auntsuncles etc Male kin recognition opens door to paternal investment Kin Recognition before amp after stable breeding bonds Image on the left black symbols represent kin recognized by Ego assuming that Ego recognizes his uncles aunts nieces and nephews Empty symbols kin not recognized by Ego Image on the right domain of kin recognition after the evolution of stable breeding bonds The contrast with the rst image is striking Prior to evolution of stable breeding bonds the agnatic kinship structure was present but socially indiscemible Paternity recognition was needed and this is exactly what stable breeding bonds accomplished Origins of Exogamy Exogamy is combination of 2 patterns found in primate lineage Between group transfer Pairbonding Early exogamy done by choice on part of females Male control of female transfers came later Women as Precious Commodities Levis Strauss says Women are important commodity of exchange Men have some level of control over women Similar in many animal species where males compete for females Sexual selection theory Postmarital Residence Where a person resides after marriage Has large impacts on the structure and size of households groups Chimps and bonobos have dualphase residence 0 Females stay in natal group until ready to leave 0 Leave group and join another to breed Dualphase residence is a phylogenetically primitive pattern Contact after dispersal In chimplike societies once female leaves a group she would lose touch with her natal kin To complete the exogamy con guration we need a mechanism for maintain contact after dispersal Chimpanzee Intergroup Relations Chimps and bonobos are territorial Avoid other groups and hostile to outsiders Intergroup ghts initiated and mainly conducted by males Paci cation of Intergroup Relations Kin recognition and stable breeding bonds set up possibility of paci st intergroup encounters Individuals would recognize a range of kin in another group Female disperses meets her natal group recognizes Father mother brothers young sisters uncles grandfather etc Males should be disinclined to attack their kin including his daughters and her offspring Creates Kinship Bridges that might pacify the groups InLaw Relations Af nity Recognizing af nes inlaws uses same cognitive processes Recognizes bonds between others 0 Bond between mother and offspring bond between spouses Brothersinlaws share vested interest in the same female 0 One as her husband other as her brother 0 Promotes harmonious relations between them Reciprocity is key For exogamy to function well bilateral transfers of females are important Similarly sized groups also important so proportion of female kin males have in their reciprocal groups is similar What about female choice Women may have more active role than Strauss or Chapais contended Choice in marital partners Choice in reproductive partners Choice in residential partners The Tribe Reciprocal exogamy creates tribelike structure where groups within tribe have relatively peaceful relations Intertribal warfare still possible and probable as bene ts of reciprocal exogamy won t apply Human residence patterns Chapais proposes that once males can peaceably interact with males of other groups different residential patterns become possible Matrilocal residence system in which a married couple resides with or near the wife s parents Bilocal residence when couples upon marriage live with or near either the husband s parents or the wife s parents Conclusion We can use what we know about primate relatives to help decipher our past Primate phylogenies useful for thinking about deep structure Must integrate knowledge of cultural evolution amp local ecology to understand variation found in human societies today LeviStrauss s concept of reciprocal exogamy although issues from an asynchronic theoretical framework is basically a primatelike or primatecompatible structure 12715 607 PM 12114 Life History Theory Focusing on trade offs and focusing on what they are Study of the key events in individual s life related to fertility and mortality Democracy is what they look at for fertility and mortality But life history theory goes beyond that and talk about things that affect fertility and mortality Time and schedule of events shaped by natural selection 0 Certain pressures in an environment that may cause a faster or shorter life history theory Demographers don t take an evolutionary view when they do their work they don t look at the ultimatelevel why questions Life History Events age at first reproduction age at menarche age when rst having sex age of first birth would likely fall shortly after this if you re not using contraception total life span how long do you live humans have a long life span mode and frequency of reproduction frequency birth spacing Contraception has a big affect on how you space your kids fecundity the ability to get pregnant at a certain time o certain things can affect this STDs nutrition etc fertility is number of children you can have parental care affects the way you allocate your time If you spend a lot of time investing in one offspring it ll show how many children you ll have Why take an evolutionary perspective You can say this is how they look but if you want to get to the wh1questions you need to take an evolutionary perspective Adaptation trait with functional role in life history that is maintained by natural selection Principle of Allocation Underlies all of lifehistory theory For any individual you have a finite amount of resources Time effort and energy for one thing limits your time for something else If you bring home a giraffe for your family to eat you can think of it as parental control but also can be under mating efforts to prove that you can support But this principle wants you to label it as one or the other Natural selection should result in optimal allocation patterns You shouldn t have such long intervals between births Where does energy go Goes into one of 3 boxes Growth Maintenance keeping your body running Reproduction o Mating o parenting Principle of allocation says your calories can only go into one box and not the other Faaso Traditional concept not scientists coming up with this definition Represents idea that you have a limited amount of resources every time you have a kid you re using up these resources Get depleted over time maternal depletion Something people see in their everyday lives Cost of reproduction Trade off 1 current vs future If you hit menarche and age 13 your growth isn t completely done for another 2 years so if you do get pregnant at age 13 there will be some tradeoffs in terms of growth and maintenance Investment in current reproduction will cost in the future If you were to wait until you finished growing you would be stocking it up to support your future reproduction Waiting and completing your growth rst can have benefits but it also has costs too Depends on things like how long do you think you re going to live If you had a species that was unlikely to live long they should be putting stock in current reproduction How you allocate this energy towards currentfuture reproduction looks at the mortality rate in that population Current vs Future Graph shows there are costs to be paid in terms of mortality by having more kids Terminal Investment Hypothesis As you age you should shift your energy towards current reproduction Your risk of death increases as you age there s also the risk of menopause Chances of having twins increase as you age Green bars 2009 statistics and are much higher because of the more assistive help you have IVF end up planting multiple eggs this is an unnatural twinning Twinning rates in blue bars double as you get older Breastfeeding rates higher among older moms Higher incidence among breastfeeding Breastfeeding for longer Reproductive Value Expected number of future offspring measured in units of currently existing offspring Will almost always talk about this value in terms of women not men The peak of the curve is menarche you would think reproductive value is highest at birth but you hit peak at menarche because there s a possibility you can die before you reach menarche Not measured by number of eggs Reproductive value declines over time Will hit menopause at some point and then can t have anymore kids Number amp Fitness of Offspring Trade off 2 Quality vs Quantity What are the survival risks Are they things you can do something about What are potential gains to reproductive success from increased investment Quality vs quantity Infant mortality rates happen really quickly diarrheal disease strikes quickly spider bites When you have high infant mortality rates you have high fertility rates this is how you re compensating rK selection Theory rselected growth fast life history want to mature quickly reproduce at a quick rate because you don t know if you ll be around for long Kselected organisms Mature slowly longer growth period Few offspring More stable environments Eg mouse vs a whale whale tends to have one baby at a time clutch size there s a reason why having the most babies possible isn t a good idea difference between producing offspring and actually having them survive clutch size how many eggs did they lay probability that any one egg will survive steadily decreases as number of eggs in nest go up there s a tradeoff between quality and quantity Best to have around 46 eggs in your nest Sex or children trade off 3 mating vs parenting invest energy in finding next mating opportunity or in offspring you already have if you re a high quality individual you may be able to tradeoff easily if the effort you put in has little impact on chances of survival you re better off shifting to mating effort Mating vs parenting greater level of obligate investment for females in many species gestation and lactation Strange Human life History long lifespan long postreproductive lifespan in women short interbirth intervals extended period of juvenile dependence male support of reproduction via parenting effort Which life history Debate about who we re supposed to be looking to as the model of human history kung widely spaced birth ache faster births 0 both huntergatherers Which one is the better model Maybe neither is the perfect fit When did life history start to change Which life history Tradeoffs differ for men and women Tradeoffs vary between individuals Tradeoffs vary within individuals I Not a stagnant concept always changing human life history is K selected Age at menarche has declined 0 Huge in uence on this is nutrition 0 Young people exerting less energy Life history theory Helps to think about optimal balance of allocation across growth maintenance and reproduction 12315 Notes from article 0 Societies with higher male contribution to subsistence are more monogamous 0 Women value male provisioning less where males bring in less food results in gender polygyny 0 When difficult for women to acquire food value male provisioning more forces males to compete via food acquisition 0 Females are the seX most in demand invest so much in gestation lactation parental care to get children reared o Crosscultural analysis of foragers reveal greater male contribution to diet increases female fertility and reproductive success 0 Women go gene shopping 0 Most mammals are Polygynous and males provide no food or direct care 0 Hypotheses l The degree of polygyny is higher when pathogen stress is higher 0 Hypotheses 2Degree of polygyny is higher where men s contribution to subsistence in lower 0 Operational seX ration OSR number of reproductiveaged women per reproductive Discussion aged men Foragers those who acquire less than 10 of diet from cultivated food2 Where it s colder male contribution to subsistence is higher and total pathogen stress is lower 0 Correlation between total pathogen stress amp polygyny among foragers due to the fact they vary with temperature of the habitat Male contribution to subsistence higher where more diet comes from fishing Percentage of Polygynous women higher where gathering contributes more to diet Degree of polygyny more strongly correlated with arranged marriage and assault frequency than male contribution Polygyny likely results from male intimidation and manipulation of other males along with female indifference or active gene shopping
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