Exam 1 Study Guide
Exam 1 Study Guide ANTH 1005
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This 29 page Study Guide was uploaded by Rachel Onefater on Thursday September 29, 2016. The Study Guide belongs to ANTH 1005 at George Washington University taught by Dr. Carson Murray in Fall 2016. Since its upload, it has received 74 views. For similar materials see Biological Basis of Human Behavior in Anthropology at George Washington University.
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Date Created: 09/29/16
Exam Suggestions: Matching—theories from lectures and also from Prof. XC: anatomically modern humans arose 200,000 years ago! Short Answer—hypotheses and characteristic point Open EndedGive an Example of… Based on X rule, should you do something, applying something in class to a particular example! Give one example of X… You have discovered X, based on Y which traits apply to X? (25 pts. Essay Question) Major Topics discussed: Socioecological theory, mtg selection, traits of primates —apply this information to a new situation —anything that is adaptive or selective has to connect to some sort of trait. Come up with a study! — Students who are most successful underline the major terms and check them off to make sure that they get covered! —Whatever you say can be addressed by that data that you collected —Should define terms, can bullet, be efficient, short sentences. Exam question on Sexy Sisters Hypothesis! Know Homo heidelbergensis Study Guide: **NOTE: Modern Humans came about 200,000 years ago Natural Selection Foundation of Human Behavior (def.) assumes that there are variation in the population, and that the environment, certain traits are more adapted, make you more competitive that helps you make copies of your genes and can force that trait to become more prevalent. ● Jean Baptiste Lamarck(17441829): "Use and Disuse" if you he observed giraffes and wondered why their necks are so long, and thought that because they used their necks so much, it got longer. Phenotypic: manifestation of other genes; the expression of genetic structure(i.e. eye color) ● Charles Darwin (18091882): observed finchesSpecies are closely related, but they have difference beak structure depending on what they eat, and each finch adapted to a particular diet. Darwinian Evolution ● Phenotypic variation ● Variation heritable ● Differential fitness( individuals with X will do better than individuals with "Y") ○ Fitness(def.) genetic contribution to the next generation, because they have a lot of genetic contribution Natural Selection Criteria 1. Individual variation exists, 2. Resources and reduction are limited 3. Competition Exists between individuals 4. Some individuals do better than others; that is, they are fitter Measuring Fitness Example: Observe longterm friendships between male/female relationship between baboons, measure what is a "real" friendship and show variation and strength in friendships, expect relationships with stronger bonds to have more offspring, how long are you going to live to produce more offspring, offspring survivorship, and age that offspring reproduces. ● When humans have friendships, their stress level is lower, and it affects your stress levels, and it affects your health! ● Within a population there are some tall giraffes and some short giraffe generations, and the population shifts as the species adapts to their environment, and those who cannot adapt, die offit is not static, things change and species adapts Three Different Types of Selection 1. Stabilizing Selection: narrower distribution and when stabilizing selection happened, there is a narrower range, there is still phenotypic variation Ex: Robins lay 45 eggs, and they can't lay 10 or 2, and as humans, we have pretty much settles on an average of one offspring 1. Direction Selection: Ex: pepper moths during the industrial revolution moths became darker because a dark moth in dark wood does not get eaten by a bird 1. Diversifying Selection: different Rabbits adapt to her environment, if it is warm, cold, snow, and adapt to the environment as to not get eaten *Can end up with new species* Phylogenetic (def.) study of the evolutionary relationships among organisms Ex: if you look at the human tree the length of the branches tells you the relationship between two different species and when the two different species diverged The Comparative Method Who is more closely related C&D or E and F? What color is E more like to B? What about X? Pattern of living species and principles of parsimony (def.) if species today express a trait, more likely than not, the ancestors did as wellnot really testable Relationships between species, can create an entire phylogeny between anger etc. Very often interested in species that are no longer alive anymore, so we look at livings species to see what it may have been like for the ancestors. Not all phenotypic change is adaptive! • Genetic drift: (def.)gene structure, esp. if it is not under strong selection (i.e. Eye color) • Founder effect(def.) only have a population in the structure that existed with the founders who came Ex: If everyone who came to the US was an alcoholic, more likely than not, people would have those alcoholic tendencies. • Bottleneck (def.) rapid decrease in population size, there s some population strain, so you end up with fewer people Ex: Disease outbreak, so we represent who survived • Gene flow(def.): Always carry gene structure somewhere else Ex: if you move from one tribe to another, you still carry the strain of genes from another tribe Not all traits are adaptive in the modern context! • Phylogenetic inertia (Lieberman)takes time for genetic structure to evolve and change, so what we are now, is probably just a result of inertia • Non‐functional DNAidle DNA that is not getting coded and is just sitting there **What matters, how did they get selected? Sources of Genetic Variation > MutationCan be an important source of variation > Recombinationcombine different DNA codes(another word for sex) Is sexual reproduction random? • Negative assortive mating is choosing a partner that is phenotypically different Promotes genetic diversity • Positive assortive mating is choosing a partner that is phenotypically similar Can lead to inbreeding depression Epigenetics is the study of how changes (inside and outside of the body) influence gene expression (also called "Soft Inheritance") Example: The earlier the offense, the greater the offense, so if your mother drinks while pregnant, you are exposed to Fetal Alcohol Syndrome. i.e. in Utero **NOTE: Does not change your genes, but changes the expression of your genes EXAMPLE: Dutch Famine, Chernobylchildren who had been born to this had horrible health consequence Studying Human Evolution: Disciplines and Tools **NOTE: Origin of the Species outlined natural selection and hardly said anything about humans and said maybe one days these ideas would help us understand about how we came to be… In The Descent of Man, and the Selection in Relation to Sex ‐ In the first part, Darwin notes the behavioral similarities between humans and other animals in terms of self preservation, sexual love, and the love of a mother for her offspring. ‐ In the second part, Darwin introduces sexual selection to explain the physical and mental differences between the sexes.very biologically determinist against women! *Victorian period saw an increase in our understanding of genetics and the onset of the persistent nature versus nurture debate. **NOTE: Twin Studies represent a very useful study system for understanding genetic influences, and nature versus nurture Monozygotic: (def.) One egg splits, identical Dizygotic: (def.) Two eggs split, fraternal Minnesota Twin Study • Directed by Thomas Bouchard, University of Minnesota • 1979‐2000 • One of the few datasets that twins separated at “birth” introversion, schizophrenia, homosexuality, introversion etc. • Twins not reunited until at least 40 • Famous “Jim twins” degree of relatedness between fraternal twins and between identical twins Adoption Studies • Changing the environment • Presumably to a more nurturing environment with more regular resources • Compare adoptee to siblings or parents look at birth family to adoptive family, and you look at the similarity the children have, if it is more with the birth family than with the adoptive family! Human Sociobiology • Application of natural selection to social behavior. • Strong emphasis on the genetic basis of behavior. push back because people do not like genetic determinism Criticisms of Human Sociobiology • Reductionist • Biological determinism • Many took issue with the hypothesis that society reflected biological imperatives. The Sociobiology Study Group wrote “These theories provided an important basis for the enactment of sterilization laws, and restrictive immigration laws by the United States between 1910 and 1930 and also for the eugenics policies which led to the establishment of gas chambers in Nazi Germany. The latest attempt to reinvigorate these tired theories comes with the alleged creation of a new discipline, sociobiology” Behavioral Ecology • Determine how individual behavior is shaped by the environment • Highlights individual variation • Interested in fitness value of behaviors in a given context; adaptive tradeoffs • Generation of formal models (e.g. optimal foraging) and hypothesis testing Ex: John Nashcost and benefits of different behaviors and different traits, i.e. game theory. People wrote mathematical models about theoretical genetic models and behaviors A Case Study: Polyandry in Tibet **NOTE: Because resources are limited and you cannot afford another wife, so they observed that the husbands are all brothers, usually the oldest is the one to father the offspringyounger sticks around because they share genes. As soon as the younger brothers had options for jobs or land, they left their families. Criticisms of Behavioral Ecology • Focuses on current fitness valueevolution has a long lens, does not tell us anything about why it came to be, it just says why it is valuable at the time! • Evolution has a longer lens with respect to adaptation • Human behavioral ecologists seem reluctant to entertain that humans may not behave optimallywe are pretty subpar Evolutionary Psychology • Emphasis that the underlying neurological structures are under selection (Ex: prefrontal cortex is pretty involved in having plans, and it stops developing at 25) • These evolved in the Pleistocene (started 2 mil. years agobrains became larger) • Adaptive lags • Focuses on the Environment of Evolutionary Adaptedness (EEA) Case Study: Disgust • Darwin (1872) argued that disgust is universal and noted that it is recognizable across Cultures, and the things we find disgusting lead to negative disease outcomes • Evolutionary psychologists argue that discuss is an adaptation that serves to guard our bodies against disease (Hypothesis) **NOTE: Does this lead to testable predictions? Example: send around pictures of things that cause diseases and things that don't to people all over the world, and people rated the pictures will level of disgustedness, and the things were correlated to disease risk were higher concordance across cultures. Predictions from Val Curtis et al (2004) P1. Disgust should be more strongly felt when an individual is faced with a disease relevant stimuli than a similar stimuli with no disease connotations. P2. It should operate similarly across cultures. P3. It should be more pronounced in females, since they have a double risk to themselves and offspring. P4. It should become less potent as an individual's reproductive potential declines. P5. It should be more strongly evoked in contact with strangers than with relatives since strangers may carry novel pathogens. Methods of Evolutionary Psychology (Tooby & Cosmides 1989) 1. Use evolutionary theory as a starting point to develop models of adaptive problems the human psyche had to solve. 2. Attempt to determine how these adaptive problems manifested themselves in Pleistocene conditions and endeavor to establish the selective pressures. 3. Catalogue the specific information processing problems that must be solved if the adaptive function is to be accomplished. Develop a computation theory. 4. Use the computation theory to determine the design features that any cognitive program capable of solving the problem 5. Eliminate the alternate candidate models with experiments and field observations. 6. Compare the model against the patterns of manifest behavior that are produced in modern conditions. Criticisms of Evolutionary Psychology • Determinism • Very limited understanding of Pleistocene conditions and grouping patterns • Can lend itself to a “just so” story *NOTE: How can we know the group sizes and if people change groups etc., could have had pair bonds, or could have acted like chimps, we can speculate, but we really have no idea! Cultural Evolution “We need a name for the new replicator, a noun that conveys the idea of a unit of cultural transmission, or unit of imitation. ‘Mimeme’ comes from a suitable Greek root, but I want a monosyllable sound that sounds a bit like ‘gene’. I hope my classicist friends will forgive me if I abbreviate mimeme to meme.” (Richard Dawkins, The Selfish Gene, 1976) Meme(def.) socially learned or transmitted *NOTE: Classic Example is Lactose Intolerance for most Mammalsselective pressure for lactose tolerance cooccurs with domestication in animals Paleoanthropology • The study of the fossil record for humankind and relatives – Incorporates aspects of geology, chemistry, and ecology (paleoecology) Archeology • Study of human activity in the past, particularly through material culture and environmental data that has been left behind tells us about dispersal patterns of individuals with tool use etc. Studies of Modern Humans • Hunter‐gatherers(def.) ecological modern pressure that shapes modern humans and these studies are invaluable! • WEIRD populationsWestern Educated Industrialized Rich and Democratic • Cross‐cultural studies Genetics • FOXP2: Gene involved in speech Phylogenetic tree, some that are silent mutations HunterGatherer Social Networks There is not really a universal people, and in modern hunter gatherers are: 1. that there are very high levels of cooperation, ' 2. 150 individuals in a group and there rare ways in which groups interact with each other, and 3. families going in between their group places, and there is a 4. division of labor men hunt larger game, and 5. women gather smaller animals or plants because they need this constancy for reproduction and lactation **A lot of variation in huntergatherer tribes Primate and the Human Body *NOTE: Primates are our closest living relatives, Humans are primates, we lump in the Great Apes species, and the Pan species like Bonobos ● Enormous variation in terms of mating rituals, tool use, and trying to understand the factors that drive that allow us greater insight into human social behavior Characteristics of Primates Forward facing eyes – Stereoscopic vision • Reduced olfaction • Several types of teeth • Nails instead of claws • Grasping hands and feet • Relatively long lifespans • Relatively large brains *NOTE: Safe to say that any kind of common human ancestor shared these traits Stereoscopic Vision: results from the fact that our eyes are forward facing, we can see 3D images and we have depth perception Helps with feeding, BUT it makes us poor in dealing with predation, so social groups can help protect from predators (greater vigilance). Color Vision Trichromatic vision (def.) the ability to see a full range of color colors can indicate what is and is not safe to eat. You can use color to tell us rightness of foods Reduced Reliance on Olfaction • Shorter snouts (in most species) • Reduced olfactory bulb in brain different types of cones Types of Teeth 1. Tell us about the dietary tendencies of different species 2. Tell us something about the species 3. Hang around forever and they have enamel and they are very prevalent in the fossil record, and more likely than not, you are able to find teeth as opposed to a full skeleton Grasping Hands and Feet *Opposable thumbs are "Really Freakin' Awesome"Answer to XC Midterm Question Long Development and Lifespan • Primates tend to live a long time given their body size •Primates tend to have long in fancy and juvenile periods before they begin reproducing *Period of childhoods, reproduction, and gestation, reproductive period, *NOTE: All species share longer lifespan and longer periods of development takes longer to reproduce, and there are relative risks to having a long delay to reproduction What are we doing for the 15 years that we don't reproduce? 1. Humans have enormous brains per their body size 2. Learning survival skills, foraging skills, social skills Large Brains Relative to Body NonHuman Primate Range Most primate species live in equatorial regions, but there is enormous variation in where primates live! Primate Phylogeny *NOTE: We care about the Pan species and apes because through phylogeny, they are closest to humans compared to other primates ● Pan species and Chimpanzees and Bonobos ● Sexual Dimorphism: difference in appearance based on sex high sexual dimorphism between males and females and bonobos, females are the dominant sex, and they food share far more than chimps, and bonobos do not conduct lethal warfare there are prosocial behaviors ● In Chimps, there are infanticide and a there is a reduction in aggression in Bonobos compared to Chimps Differences from Other Primates? 1. Bipedalism Advantages of Bipedalism • Efficient terrestrial locomotion • Freeing of hands – Carry things (i.e. babies), make and use tools • Efficient foraging • See distancespredation, food • Keep cool Disadvantages of Bipedalism • Slowerputs us at risk of predation • Less stablebecause we only have 2 feet • Limited climbing ability • Back problems because of Sshaped spine • Obstetrical dilemma – Pelvis size and shape constrained by bipedalism Why Did Bipedalism evolve? What hypotheses are discussed in The Story of the Human Body? 1. Ecological adaptation geared towards getting food (move further distance for food) 2. Carrying tools/foodfree hands to make toolstech and material culture are important 1. Dismissed this because: bipedalism was not a result of making tools or vice versa 3. Male Provisioningsexual Division of labor suggest competition between males and not wooing females 1. Dismisses this because: there is still a lot of sexual dimorphism 4. Bipedal because they have to walk through waterwade through wateraquatic ape hypothesis which surrounds become bipedal to navigate through water(dismisses this) Which has the best support (according to Lieberman)? A: Socioecology Theory: Ecological adaptation geared towards getting food (move further distance for food)landscape of food patches that primates have to move across, but when you have a change in climate and a change in landscape=changing resource distribution to get the food to meet their needs 1. Skin ● Hairless ● Sweat glandsdilute compared to other mammals 1. Human Skull • Large, rounded skull – High forehead, no brow‐ridge • Small, flat face with protruding chin • Smaller teeth 1. Large Brains Relative to Body Size Allometry:the growth of body parts at different rates, resulting in a change of body proportions body size. *NOTE: This will be an exam questiondraw a diagram to exhibit understanding : What you need to know Trans 1: Beginning of Bipedalism Orrorin tugenensis ~6 mya Ardipithecus ramidus ~4.4 mya Trans 2: Australopithecine Diet • Gracile (A. africanus, ~3.3‐2.1 mya) – Rounder skull – No Sagittal crest – Prognathous jaw • Robust (P. boisei, ~2.3‐1.2 mya) – Sagittal crestoccurs in carnivores, and attached to jaw bone – Flatter face – Massive cheekbones and jaw *NOTE: Each species does things differently than one another diversification of dietary strategies because of sparse environment Trans 3: Towards More Modern Bodies • Homo habilis (~2.3‐1.4 mya) – Larger brain and flatter face than australopiths – Small, australopith‐like body • Homo erectus (~1.89 mya ‐ 143,000 ya) *NOTE: Modern humans existed with these species – Shorter arms and longer legs – Modern feet – Smaller teeth – Larger brain – First to leave Africa Niches(def.) ecological niche space that you use, so you could have had a different niche than other species Trans 4: Anatomically Modern Humans • Lighter skeletons • Larger brains • Thin walled, rounded skull • Less (if any) brow ridge or prognathism • Small jaws with smaller teeth • Likely evolved in Africa Homo heidelbergensis ~700,000‐ 200,000 ya Out of Africa 1. Homo erectus (left ~1.8 mya) 2. Homo heidelbergensis (left ~500,000 ya) DIRECT HUMAN ANCESTOR not behavioral, but more genetic (i.e. body size) 3. Homo sapiens (left ~60,000 ya) What about Neanderthals (Homo neanderthalensis)? • ~400,000‐40,000 ya brain is larger per body size when compared to humans had burials of indiv. with flowers, very sophisticated art and rituals Hominin(def.) group of humans direct ancestors, particular those that are named Homo Hominid(d ef.) tax including the Great Apes Model of Evolutionary Change and Adaptive Benefits Are Humans Monogamous? Social vs. Sexual Monogamy How long does a pairbond last? Social Monogamous: "seen" with one partner for an entire lifetime (i.e. often religious bound) Important for reproductive success! Sexual Monogamy: They have sex with more than one person *NOTE: Most societies are not monogamous Preindustrial Mating Systems Monogamy is not very high More often, polyandry is very low Polygyny happens quite often, so less than 20% of individuals in societiesmeans that it is accepted, not that all those individuals are actually in polygamous relationship Monogamous (def.) one male, one female Polyandry(def.)one female multiple males Polygyny(def.)One male, multiple females Polygyny Example: Ismael the Bloodthirsty; he fathered 888 children Male reproductive potential is so much higher than a female mammal, no females species EVER can reproduce like a male can! Number game: how many sperm and eggs a male and female have Are there adequate resources to have multiple wives and multiple children? SocioSexual Index (SOI) *NOTE: Lower scores are more monogamous, and higher scores mean that you are more promiscuous! Index to Ring Finger Ratios *All this reflects is really levels of testosterone (which is a biological composition) for BOTH men and women! Males have lower testosterone receptors compared to males in other species SocioEcology and Sexual Selection Q: What males and females are strategizing to do? A: We all want to reproduce, to perpetuate our own genes, at least from an evolutionary perspective! Related to behavioral ecology: look at behavioral variation as it relates to ecologic pressures. What are some of the costs and benefits of being social? Socio‐Ecology: The study of how social structure and organization are influenced by organisms’ environment Benefits: 1. Can increase group vigilance 2. Cooperation(i.e. tasks, breeding) 3. Ecological Knowledgelearn new things from older and and more experienced species. 1. Easier to Find mates Costs: 1. Conspicuous 2. Competition for Resources 3. Disease Transmission Reproductive Asymmetry Females have already invested a great amount of time in the offspring, so they will do the same once the offspring is born! Reproductive Potential • Female reproductive potential limited by access to foodhuman females need others to help! • Male reproductive potential limited by access to mates, there are so many fewer eggs and women who are receptive(ability to conceive after already giving birth is low)! Females are the ones who are driven by access to food, they may be social at the resource of the food. Friendships and cooperation would affect your access to resources Through contest competition, you end up with dominance and hierarchies to help you defend the resources Social relationships become more competitive in contest competition! Competition • Within‐Group vs. Between‐Group competition When you have more individuals in your groups Ex: Georgetown and GW, what is good about having a larger group? The larger groups should be able to outcompete smaller groups(all things being equal), BUT the larger groups have more competition! Dominance *Sisters will help you compete and sisters ware very investing reproductive success because you have the same genes, it does not matter if it is your own children! Males may have to leave because of inbreeding if women stay together to increase their chances of reproductive success with their genetic makeup Dominance rank may have significant fitness consequences • Chimpanzees from Gombe National Park, Tanzania • High‐ranking females give birth more frequently • Offspring of high‐ranking females are: • More likely to survive • Mature faster Sex‐biased Dispersal • One or both sexes disperses (emigrates) at sexual maturity to avoid inbreeding (Inbreeding Avoidance Hypothesis) • Philopatry (philopatric sex):remaining in the natal community • What is the typical dispersal pattern in mammals? Do primates follow this pattern? Overwhelmingly, the males tends to be the ones that leave during sexual maturity Example when Females Stay: Spider monkeys, Chimps, Bonobos Reproductive Skew: High variability of reproductive success Example: Mountain Gorillas, a very high proportion of offspring are going to one group of males, and a lot of the male gorillas will have no offspring Alpha male gets about 3340% of the offspring Physical body size and weaponry is very important Canines are used, not for eating food, but for fighting and biting *NOTE: Reduction of malemale competition among humans Sample study that would test whether physical size correlates with reproductive success of male primates: Experiment 1: You would compare and group different men into height, weight, and build, and then compare each of these groups of people to average amount of offspring each group has sired and compare this to men who are not in their height, weight, or build group. Should also look at how well those babies do! (i.e. survivability and ability for the offspring to produce offspring). Experiment 2: You could also do a longitudinal study with multiple generations and observe if they grow in size over generations depending on how many offspring they have Can look at different populations and different species. *NOTE: Can also do between species comparison! Q: Do I see a positive relationship between reproductive skew, and does that correlate to dimorphism? *NOTE: The outcome measure, which the reproductive variance is lower among humans is different than in other primateshumans have a much more reduced reproductive skew Exceptions: • Female mountain gorillas associate permanently with males, despite low predation risk and no benefit to foraging together • Mantled howler monkeys have high levels of female‐ female aggression and female evictions, but no formal signals of submission or nepotistic hierarchies Sample Scenario: What happens to a frugivore species in terms of female competition, social bonds, if there are resources that are defensible and heterogeneously distributed? A: Depends on how clumped the resources are in space and time, but if they are clumped, women would not disperse and they would stay with others, and family would be the ideal coalition partners because of the similarity in genetic makeup. If it behooves them to form coalitions, they should be doing it with their relatives if females cannot defend their resources, they would be expected to disperse to different environments. ● Enormous consequences for those individuals are dispersed over space (i.e. warfare, mating). Human Socioecological *NOTE: 10,000 years ago is where we have the first crops/transitioning to agriculture. People are staying in the same place versus huntergatherer lifestyle Agriculture lends itself to greater competition because your resource is concentrated in one place, so there is a need to defend those resources. ● 10100 people in a band, though much larger in provident habitats. Many bands make up larger tribes. Group size predicted for extinct hominins from the strong relationship demonstrated between neocortex ratio and group size among plant primates. Human Social Features: 1. Multifamily group as modal group type 2. Monogamy/polygyny mix as modal mating system 3. Variable levels of premarital and postmarital sexual promiscuity 4. Cooperative mate selections (marital arrangements) 5. Fatheroffspring recognition based on stable mating bonds 6. Lifetime bonds between dispersed kin, in particular between crosssex kin 7. Bilateral kin recognition (mother's and father's sides), independent of coresidence 8. Bilateral recognition of affines(husband's and wife's sides), independent of coresidence 9. Exogamy and dual phase residence(def.) mate and marry outside of our bands, but inside your tribe 10.Bisexual residence and dispersal; hence, flexible residence patterns 11.Strong bonds between interbreeding groups based on biological and affinal kinship 12.Nested organization of social groups 13.Groupwide coordination based on shared objectives 14.Multigroup coordination 15.Number of nested levels of Social Organizations *NOTE: Individuals share with each other, likely because of kin bonds Cooperation(reciprocity) helping, but going to get something back; form alliance and help you raise your family and feed your family. No other species provision weaned individuals, and this is unique to humans Weaned:are no longer feeding of breast milk Distinctive features of the evolved human production system that have direct implication on human organization: 1. Skillbased 2. sex based complementarity in skill acquisition 3. Gains from cooperation promote linkages 4. nondefensive resource(economic defensibility) *NOTE: Can and should share because the resources cannot be monopolized Derived traits(def.) those that we think are continuous with what existed before, even though they may be different from past traits compulsive sociality community structure at root of organization multimale, multifemale communities malekin bonding female transfer predominant intergroup hostility( because of mates or territory) larger community sizes exploded or extended fissionfusion Extension of kinship structures through the generation of formations of lineages organized(female) mate transfer Strong malefemale bonding and persistence of relationships higher pattern investment etc. Novel Traits: completely new traits and there was no trace of these traits in the past Plesiomorphic traits: shared traits, least common ancestor had those traits already multimale, multifemales community structure male resident, female dispersal on maturity weak malefemale bonding and inter community hostility Male hierarchy female hierarchy Australopithecus afarensis. The first Family? not necessarily obligate bipedal, but within these larger nested organization, there were greater pair bonds about 3 million years ago (potentially). Sexual Selection and Mate Choice Access to resources is going to matter, access resources to lactate, and raise offspring, and ambition Prosocial and positive behavior Problem solving ability, conflict management Sexual Selection Natural selection for traits associated with mating success Underlying premisevariation in reproductive success Acts different on males and females Two types of sexual selection: 1. Intrasexual selectionwithin one sex 2. Intersexual selectionbetween the sexes Intrasexual selection: ● One sex competes for access to another ● Usually males competing for females ● Favor traits that enhance competitive ability ○ Many different kinds of traits can make males between competitors Sexual Dimorphism: ● Males and females differ phenotypically in many species ● Difference reflects the intensity of intrasexual competition ● Intrasexual competition is most often more intense in males (Bateman Principle) ● Higher dimorphism correlates to higher skew in reproductive success ● Fighting and ornamentation ● MaleMale competition often does not stop with successful mating. There is often postcopulatory competition. ● This type of intrasexual competition is called, SPERM COMPETITION. ● Can get pregnant within 710 days when sperm is inside of you Evidence of Sperm Competition in Primates High degree of promiscuity, the testes are very large For monogamous species, testes are smaller those species that have multimale groups have very large testes per body size because males are competing with other males. ● Allometrysomething scale to something else *NOTE: Sperm Features suggestive decrease in intrasexual mate competition in human evolution ● Small testeslow motilityhigh percentage of abnormal sperm InterSexual Selection: ● Between males and females ● Difference in attractiveness to the opposite sex ● Usually nonrandom mate choice by females ● Why? Sexual Selection Theory (Review): Natural selection with traits associated with mating success has to be variation and some phenotypes have to do better than others. >The form of Sexual selection is directly related to the relative investment in offspring production >The sex that invests in more offspring production has fewer reproductive opportunity As a result they, ● Should be more choosier Evolution of Elaborate Displays ● The theory of sexual selection is most famous as an attempt to explain the evolution of exclusively elaborate adornments and displays ● Although some elaborate displays may have evolved for use in contest between males a, some have certainly evolves as a result of selection by females for genetic benefits (ex: peacock). What are females choosing? Resources and/or physical benefits? 1. Direct benefits: Territory, food, provisioning, parental care female hanging flies mate with a male only if he provides a large nuptial gift. Copulating for a longer amount of time should lead to greater amount of sperm Bigger gifts earn reproductive benefits 1. Indirect Benefits: Good Genes or Sexy Sonsthings that are encoded genetically that have downstream positive effects **Something to considerFacial Coloration? Good Genes Hypothesis *NOTE: Elaborated male traits may be indicators of heritable genetic qualities (i.e. fitness). The Handicap Principle (Zahavi 1975) Males may have a heritable trait that reduces viability. But males with good genes can survive the handicap. If females mate with those males preferentially, their offspring will inherit that trait and so forth and so on… Handicap Principle (def.) Assumption that the trait carries continuously and that the bigger/more pronounced traits are more costly. The trait is an honest signal since there is a true cost to the elaborated trait the prevents 'cheaters' Sexy Sons Hypothesis Fisherian Runaway SectionCorrelation between a trait and female preference ● Trait can evolve way beyond being an honest signal. ● The trait itself can become a fitness burden ● The process can therefore come to a point where the ONLY benefit to female choice is that her sons inherit the most attractive traits. *testable because you can look at fitness costs and benefits How does sexual selection influence human mate choice? Important Distinction Social v. Sexual monogamy Shortterm vs. long term mate choice ● What are men looking for? ● What are women looking for? ● Does timeframe matter? Choosiness in Women versus Men Men and women are both choosy when it comes to a longerterm mate 1. Women are much choosier about casual sex than men are 2. Both sexes are choosy at you move up to longterm dating/marriage partners ● Men Prefer Youthfulnesscrosscultural/universally known ○ This matters because it has to do with offspring count, and so you can see that there is a fitness cost, so it makes sense for males to select a younger mate because there are more years of reproductionprobably driven by menopause ● Women prefer Wealthcorrelates to resources/genes ○ Difference of earning potential and mate choice and women have a preference for older men, but there is a positive correlation between wealth/stability and age! ● Honest signals ● Health, fertility, and compatibility ● Body Shape ○ Women: figure is an honest signal of fertility ○ Men: Correlate to T? Men with higher SHR have sex earlier and have more partners ● Facial Symmetry ● Body Odor ● "Mate Copying" ● Voicedeeper voices correlate to testosterone production Smell and Mate Attraction Pheromones: chemical signals that lead to a behavioral response Ex: Male silkworm moths travel 30 miles to find a female, following her pheromone trail & in humans pheromones are released during the late follicular phase that synchronize female menstrual cycles *NOTE: Also linked to sexual attraction in both men and women Shortterm Mating Strategies One night Stands: brief and nonexclusive *Female and family deal with the consequences of parenting Extra Pair Copulations: male partner may deal with consequences; one individual mates outside the pairing Shortterm mating: premaritalextramaritalmate poaching *Note: Extra pair copulations and mate poaching are common amongst birds despite social monogamy Cuckholdry: male invest in offspring from another male Health Risks and STM HPV: 50% of sexually active men and women in America will contract Chlamydia: 2.8 millions Americans each year will contract HIV/AIDS: 64% in SubSaharan Africa; 30% South and Central America ShortTerm Preferences for Men ● Men tend towards fertility in the longterm strategy(honest signals and youth) ● Standards relaxed in the shortterm ● Closing time phenomenonincrease pool of potential partners ● No long term commitment ● Decreases ability to pursue shortterm encounters, increase demand for investment Male Promiscuity and Attractiveness ● Most likely to engage in shortterm strategies when they possess physical features most valued by women: symmetrical features ● Women seeking shortterm encounter are more concerned with physical attractiveness ● Male mate guarding may increase in less sexy men who are good providers when their partners are fertile **NOTE: Alternate strategies based on likelihood for mating success Shortterm Strategy in Women ● High frequency of male shortterm mating requires: willing females ● 2050% of American women reported having an extramarital affair ● Orgasms important ● More sperm retained ● EPC likely to coincide with ovulation ● More likely to orgasm with shortterm partner What Women Gain from Short Term Mating: ● Resource Hypothesis: paternity confusionprotectionstatus enhancementmate switching if current partner cannot provide ● Genetic benefits Hypothesis: sexy songenetic diversitygood genes Support for Good Genes ● Symmetrical men tend to engage in short term encounters with more women who are already in relationships ○ Do not experience benefits of longterm commitment ● Attractive men are favored for shortterm mate because women want other women to find their partners attractive ● Women more likely to have a shortterm mate during ovulation ○ More attraction to masculine features ■ Prominent brows ■ Large Chins ■ Deeper Voices ○ Markers of testosterone and immunocompetence Mate Poaching ● Pursuing a short term mate who is already in a relationship ○ 60% of men ○ 40% of women ○ 10% of relationships ● CrossCultural study supports this universal, both sexes participate but males so more often Human Mate Poaching a Conditional Strategy? ● Mate poaching has two intentions: 1. Shortterm poaching 2. Terminus in formation of new, long term relationship ● Conditional strategy if poacher does so when he/she cannot find a mate of sufficient attractiveness who is unattached Q: Contextdependent? Are there socioecological factors that favor mate poaching? Answers: Benefits of Mate Poaching for Men: 1. Egoboost from challenge 2. Passing genes Benefits of Mate Poaching for Women 1. Higher Quality mates (good genes, sexy sons) 2. Provisioning? Costs of Mate Poaching for Men 1. Risk of escalated challenge 2. Punishment by mate?Loss of Partner? Cost of Mate Poaching for Women 1. Bad reputation 2. Lack of Support from Partner 3. Physical Harm by Partner Homosexual Behavior ● Difference between homosexual behavior and not reproducing, they can still reproduce, so it's not so bad if in most species, or even in humans, they are reproducing! ● Huge variation in cultural acceptance around the world from where are best places to live if you are homosexual! ● Many subSaharan and African countries have very strict laws regarding homosexuality and it may be punishable by death ● The more religious you are or your area it's, the fewer tolerance there is of homosexuality and viceversa ● Genetic basis for the behavior of homosexuality ● Homosexuality is more common in brothers and relatives on the same maternal linewith sons and brothers ○ Similarities in certain sections of the Genomeif indiv. Who score themselves with sexuality have a high constancy of reticular sections (i.e. is there a shared gene), and there are some (6070% of men who selfidentified in the study have this gene) ● Some 400 species engage in homosexual activity, including bonobos(male and female) which are closely related to humans ● In some cases there are reproductive reasons, e.g. male Goodeid fish mimic females to dupe rivals ● Longterm preference for same sex mates is rare, but 6% of male bighorn sheep are effectively "gay" ● Woman have more sexual fluidity and can find women having sex with each other is attractive, even if they will never have sex with a woman when compared to men ● Only 20% of identical twins are both gaygene by environment interaction ○ Can use this argument to argue for or against the genetic aspect of homosexuality Evolutionary hypothesis Assume there is some genetic basis to homosexual behavior? How could this be adaptive? ● Maybe they just reproduce! ○ People were in heterosexual relationships and had homosexual lovers, and they were still able to reproduce ○ Gays and lesbians do have children (37% of LGBT couples have children, 60% of which are biological) ● Genes that code for homosexuality carry other benefits ● 'Helper at the nest' ● Promotes social bondsif malemale bonds are important to some aspect of reproductive success, on man is better to help another for conflict, sexuality is tied up with friendship and sex (i.e. oxytocin and testosterone) Sexy Sisters? The same traits may make the oppositesexed sibling more attractive and/or have higher fertility. Evidence the sisters of homosexual men are more fertile! replicated in many different populations Helpers at the Nest >Men who dress as women and have sex with men and are considered as a third class of individuals are revered in societyAffafeen individuals Spend a lot of time with their nieces and nephews Lacks support in several empirical studies Promoting Social Bonds ● If homosexual tendencies and behavior go along with forming samesex bonds, an aside to a need and importance for femalefemale friendships and malemale friendships ● About the importance of samesex bonds to fitness (Ex: Single mom, it would help to have female friends, and you can have sex with them, it does not matter) ○ Those bonds are often stronger if sex is involved ○ Evidence needs to help promote reproductive fitness Immune Hypothesis ● Later born individuals are more likely to be gay ● Men are about 1/3 more likely to be gay for each additional brother. ● Odds of being gay are about 2% for first borns, 3% for seconds sons…etc. ● No relationship between birth order and the probability of being a lesbian ● Every time you have a son for a Mom, you are carrying Y chromosomes and you are circulating Y chromosomes, and male sons are different to the female body and gets interpreted to the allergenbody rejects ● What happens with each son is that you get more antimale, antiY antibodies, we are more likely to miscarry with later born sons and you are able to mount a stronger defense with time, and we see this as an allergen The later sons you have are: ● lower levels of testosterone, ● smaller in size ● more likely to be homosexual Human Life History Life History Theory: the age‐specific reproduction and mortality rates, and the entire sequence of changes through which an organism passes in its development from conception to death > timing of every developmental process including death that everything that passes through from birth to death, order in which they happen and the timing in which they happen, and how they relate to reproduction Ex: Possums vs. Elephants, number of offspring is different for different animals How many kids to we produce? How often do we have children? Life History Variables Gestation length Age at weaning: how long to they nurse for? Age at first reproduction Inter‐birth interval: Period between one live birth to the next Litter size Maximum life span Trade Offs • Current vs. future reproduction Ex: if you nurse your daughter until she is 6 years old, that means you are not ovulating(women are not ovulating when they are nursing) , so you cannot invest in your next reproduction mammalian tradeoff • Quantity vs. quality of offspring Ex: Species that reproduces a lot of offspring, it is more of an insurance policy (i.e. high mortality rate, and this is more of a quantity strategy as opposed to humans that have a quality strategy (i.e. low mortality rate) Extrinsic mortality: risk of death that is not dependent on an organism's behavior > disease risks, predation risks (i.e. environmental risks) Intrinsic mortality: risk of death associated with how an organism allocates resources towards somatic and reproductive effort. > internal factors like how we allocate our energy, energy is finite Survivorship Curves • Specialized camera to measure skin luminance and skin color • No change in luminance, but redness increased around ovulation • BUT men could NOT detect changes in redness … So??? r/K Selection • r‐selected species (Ex: Possum) r=rapid – Many offspring – Low investment per offspring – Low offspring survival – Small body size – Early maturity – Short interbirth intervals • K‐selected species (Ex: Elephant, Humans) – Few offspring – High investment per offspring – High offspring survival – Large body size – Late maturity – Long interbirth intervals Compared to other mammals of similar size, primates(kselected species) develop slowly and invest heavily in offspring Primates have: • Long gestation lengths • Long developmental periods & late ages at maturity • Low reproductive rates (i.e., they reproduce slowly) • Long lifespans = anything in red is UNIQUE to humans Gestation: Conception to birth. Rapid organ growth and development Infancy: Birth to weaning. Dependent on mother for nutrition and protection. Weaning: No longer dependent on you mother for milk and nutrition Childhood: Weaned, but dependent on others for food. Juvenescence: Weaning to sexual maturity. Travel and forage independently. Period of learning and body growthlow mortality risk! Adolescence: Onset of puberty to sexual maturation. Period of rapid body growth Adulthood: Attainment of adult body size and sexual maturity *Why do humans have a very long postreproductive lifespan? A: Can be an artifact of our environment (i.e. technology) Human Fertility Mammals can be "k" or "r" selected species Primates are going to be below some other mammals because they are "k" selected ,and non human apes are less fertile than humans because of longterm pair bonds and help from other individuals! One of the reasons that we are thought to have such a large neonate size, and a lot of that surrounds the process in which we (humans) get big brains! We grow such big babies per body size because our brains got bigger, so we have a very large brain per body size and this coincided with: 1. Tool useacquire and process food more easily 2. Cooperative breeding(presumably) Brains Are Expensive • Percentage of adult RMR(resting metabolic ratei.e. "chilling") devoted to brain: 20% in humans *NOTE: in young children 8060% of RMR goes to brain growth 8‐10% in other primates 3‐5% in most other mammals Obstetrical Dilemma pelvis got short with bipedalism Obstetrical dilemma: idea that the brain size, head size, and birth time in constrained very much by pelvic size so a lot of brain development has to happen postnattily; may have been challenging even for Homo erectus Modern humans have a lot of fontanel: space between the bones of the skull in an infant or fetus, where ossification is not complete and the sutures not fully formed. The main one is between the frontal and parietal bones. Postnatal Brain Growth Later birth chimps and do not do a lot for brain growth, but humans do have a lot of brain growth Brains stop growing between 21 and 22, prefrontal cortex is that last to finish developing at around 25 Secondary Altriciality: We have a long period of dependency in which we support brain growth Altriciality: needing nourishment Human Life History • Relative other Great Apes – Long lived – Late age at maturity – Short infancy – Short interbirth intervals – Large adult brains
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