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Date Created: 02/10/15
Evolution What is evolution 0The process by which biological diversity is produced 0The concept that underlies and unifies all biological sciences including biological anthropology What if we aren39t alone OHome Sasquatchensis Homo Yetti Things only modern humans do OLarascopic gastric bypass surgery riding seqways hair metal the list goes on Evolutionary Framework 0How is human evolution similar to and different from that of other primates and other organisms 0Levels of adaptation in humans Cultural and behavioral adaptation Biological adaptation Genetic adaptation Acclimatization Developmental acclimatization OThe eternal triangle genotype environment and culture Describing Human Variation OHistorical approaches to describing human variation OSkeletal variation and its application in fields such as forensic anthropology 0The original task of biological anthropology 00ften conformed to or was used to further political agendas OHistorically conceptualized as race but what does race mean Is it a valid concept 0How do we quantify and describe human variation 0What is the relationship between phenotype and genotype in modern humans 0How does society deal with human biological variation 0Most variation in Africa most ancient lineages in Africa Modern Notions of Race Biological VS Sociological Concepts of Race Applying Knowledge about Human Variation Bioarchaeology and Forensic Anthropology Skeletal Variation sex age ancestry size anomalies pathologies and trauma Understanding Modern Human Variation difference between describing and understanding Understanding Contemporary Human Biological Variation 0Using an evolutionary and biocultural approach to deduce the mechanisms that produced the patterns of variation we observe and describe 0The pattern we see today are the result of the action of evolutionary forces mutation selection gene ow genetic drift acting in the past and the present OPatterns that re ect adaptations to different stressors climaticenvironmental nutritional psychosocial etc are of particular interest Extant Hominoids Gibbions orangutans bonobos chimpanzees gorillas humans Why do we see so much phenotypic variation in living humans today when there is very little genotypic variation ORecent origin win the last 200000 years and wide geographic distribution 0Wolves like humans are widespread and variable variation re ects patterns of gene ow and isolation and adaptations to diverse environmental factors OSome variation re ects adaptations to the environment ex sherpas good at hauling people up Mt Everest OLactose tolerance Lactase persistance an adaptation to a cultural practice pastoralism that allows adults to digest milk Lactase Persistence OLactose is a sugar found in milk most humans become lactose intolerant after weaning because lactase the enzyme that digests lactose production ceases during adolescence OLactase persistence in human populations is correlated with the domestication of large ungulates and consumption of dairy products thought to confer selective advantage 0The alleles responsible for lactase persistence differ by population indicating independent origin Human Biological Variation and Health Evolutionary medicine the application of evolutionary explanations to questions of human health Evolutionary Darwinian Medicine 0Biology is the foundation for all medicine yet evolutionary biology has only recently been recognized as being important to health Evolution of Disease 0We know a lot about why individuals get specific diseases but much less about why diseases exist at all 0 The great mystery of medicine is the presence in a machine of exquisite design of what seem to be aws frailties and makeshift mechanisms that give rise to most diseases Nesse and Williams The Role of Evolutionary Medicine 0Why hasn39t the process of natural selection eliminated the genes that make us susceptible to disease 0Why hasn39t it selected for genes that would perfect our ability to resist damage and enhance repairs so as to eliminate aging Proximate vs Ultimate Causes OPhysiology genetics biochemistry etc generally concentrate on proximate causes 0What and How questions 0The immediate mechanisms that give rise to disease disorders and malfunctions 0Ultimate causation how evolutionary processes and evolutionary history shape traits OWhy questions OHow natural selection and other evolutionary forces shaped the trait under construction OTraits have both types of causes a complete biological explanation requires analysis of both The Evolution of Obesity OObesity seems very simple energy imbalance with too many calories in and not enough calories spent OObesity is actually a staggeringly complex condition with genetic environmental and developmental components OIncreasing global prevalence obesity virtually nonexistent in foragers rare in preindustrial food producers major increase in overweight and obesity in both adults and children in the US today obesity affects 311 of men and 332 of women in the US rapid increase in both developed and developing nations 0can be considered an epidemic The Contributions of Western Diets OEnergy dense and highly caloric with major contributions from refined carbohydrates sugars and grains and fats especially saturated OFairly low in protein 15 of total calories 0Raises the question are we adapted to eat certain foods or a particular diet Proximate Causes of Obesity OProximate energy balance intake vs expenditure 0 genetic factors play an important role appetite control BMR fat deposition etc Oreduced activity levels present evidence suggests that below a certain EE levelthreshold there is a breakdown of regulation of energy balance l8 PAL OCertain highly energy dense foods especially as liquids override the system and facilitate excess consumption 0humans have a weak ability to downregulate food quantity with very highdensity foods high fructose corn syrup in soda and other sugars increased more than 1000 from 1970 to 1990 Ultimate Causes of Obesity OEvolutionary perspective human fatness unusual for tropically adapted species including primates 023 in females and 13 in males average for nonWestern adults OPrimarily related to nutritional buffering Ohuman propensity to deposit fat when food available 0Role of brain size 0accumulation of fat in women during pregnancy 0fat accumulation in prenatal and early postnatal life 0Links between fat and reproduction 0sexual selection fat patterns and amount female attractiveness 0role in regulation of reproductive function though not simple Nutritional Availability 0Humans are adapted to buffering periods of limited energy availability OHistorically underwent relatively long periods of limited nutrition days weeks or even months ORelatively unpredictable uctuations in energy availability OPossibly led to evolution of thrifty genes Are Humans Still Evolving 0Until recently the answer was thought to be No OHumans beyond evolution reached peak 0Food production and population expansion OTechnology modern medicine Humans are Still Evolving OMultiple evolutionary forces are still acting on us even in our humanmade environments 0Evidence for evolution since the beginning of food production evolution did not stop with the advent of agriculture 0Persistence of variation in modern populations sickle cell allele lactose tolerance etc 0Continuing in uence of natural selection malaria resistance lactase persistence skin color skeletal development etc The Race Concept Growing Awareness of Human Diversity 0Ages of Discovery and Imperialism 15th early 19th centuries brought western Europeans into contact with diverse and unfamiliar peoples OGrowing recognition of European prehistory and cultural evolution Early Scientific Approaches OCarolus Linnaeus 1758 Systema Naturae included first systematic attempt at human classification 0Most early 18th and 19 century classifications used some type of ranking system Great Chain of Being in Scala Naturae OLinnaean Taxonomy an example of preevolutionary typological concepts of human variation that still inform the way race is conceptualized today Birth of Physical Anthropology OPhysical anthropology began as the study of modern human variation no human ancestors were recognized until the 1850s OPhysical anthropology initially a technique for documenting variation rather than a theoreticallybased science aimed at understanding variation Johann Friedrich Blumenback 1752 1840 0The father of physical anthropology 0in 1775 described five major divisions of humankind Caucasoid Ethiopian Mongoloid American and Malayan 0drew links between skin color head size and shape facial shape geography percieved intelligence and behavior Samuel Morton 1799 1851 0Philadelphia physician and naturalist OOne of the founders of American physical anthropology OAmassed collection of over 3000 skulls to document superiority of Europeans OBelieved that races were separate species OWork debunked by Stephen Jay Gould in The M ismeasure of Man 1981 Typological Concepts of Human Variation OLinnaean classification 1758 included five varieties of Homo sapiens Americanus Europaeus Asiaticus Afer and Ferus OBlumenbach described five major divisions of humankind Caucasoid Ethiopian Mongoloid American Indian and Malayan 0Europe and America 1700s and 1800s popular theory of polygeny held that human races were separate species An Era of Measurement OSkeletal differences between groups focused primarily on differences in the skull especially in the face OAnthropometry the physical measurement of human body form OCraniomentry size and shape the study of cranial measurements OCephalic index widthlength x 100 CI 0lt75 dolicocephalic longheaded 075 83 mesocephalic medium headed 0gt83 brachycephalic roundheaded The In uence of Scientific Racism 0Scientific racism and works such as The Passing of the Great Race 1916 in uence American policy and Nazi philosophy 0Johnson Reed Immigration Act of 1924 the Act limited the number of immigrants who could be admitted from any country to 2 of the number of people from that country who were already living in the US in 1890 this privileging western Europe completely prohibited immigration of East Asians and Asian Indians Othese quotas were not repealed until the passing of the Immigration and Nationality Act of 1965 Eugenics 0The philosophy of race improvement or the idea that controlled selective breeding can improve the human species OAdvocated by Francis Galton 1822 1911 0At least 60000 American were sterilized against their will in 1935 Summary 0Most early studies of human variation were focused on description and classification not understanding OPhysical anthropology began as a technique to describe and classify modern humans 0Early studies of human variation shaped by European colonialism and ethnocentrism OEvolutionary theory provides a framework for understanding human variation but early attempts were problematic and used to justify discrimination Modern Notions of Race Biological vs Sociological Concepts of Race 0Common notions of race characterized races as bounded groups that can be described by distinguishing features assuming that they are basically closed systems and that mixing can occur between them Key Events Leading to the Demise of the Race Concept 0New understandings of evolutionary theory brought about by the modern evolutionary synthesis 0Recognition of the extent of human plasticity in response to environmental factors ONew understanding of variation within and between populations in different phenotypic traits 0Social climate of the time and rejection of scientific racism 0Application of standard criteria for recognizing species and subspecies The Modern Synthesis 0The integration of Darwinian theory Mendelian genetics in the 1930s and 1940s 0Focus on populations interbreeding groups of individuals variable populations instead of fixed types 0change in geneallele frequencies over generational time evolution Opopulations evolve individuals do not OTheodosius Dobzhansky Ernst Mayr George Gaylord Simpson Modern Perspective on Human Variation OJulian Huxley a founder of the Modern Synthesis underscored importance of variation within rather that between human populations OProposed that variation within the European population allowed 3040 of the population to survive the bubonic plague Biological Concepts of Race 0 race is a term originally borrowed from biology 0According to evolutionary biologist Douglas Futuyma race is a vague meaningless term sometimes equivalent to subspecies and sometimes to polymorphic genetic forms within a population OSubspecies are difficult to define but usually distinguished by certain characters of allopatrically distributed separated by distance or geographical barriers Franz Boas 1858 1942 0Pioneer of modern scientific anthropology OIn immigrant studies 1912 found that mesocephalic European immigrants to America had dolicocephalic children 0Attributed to differences in bedding styles hard cradles vs soft beds ODemonstrated that cranial shape was plastic Cranial plasticity cultural practices cranial deformation was very common in the ancient America 00ther 19th century studies documented variation in growth based on socioeconomic factors 0Re ection of environmental factors experienced during growth and development OSecular trends changes in phenotype that occur over generational time ORe ect not genetic changes but environmental shifts Sociological Race 0 race is also a sociological construct 0a way that humans categorize each other that governs how we behave with each other and forms a large part of individual identities Ooften con ated with notions of biological race and assumed to describe biological or genetic characteristics Five Reasons Why Race Does not Adequately Describe Modern Human Variation 11t is difficult or impossible to draw geographic boundaries between human groups 2Traits are not clinically distributed and the distributions of traits do not coincide or overlap as one would expect if concepts of race were accurate 3There is little agreement on how many races there are even among proponents of the race concept 4The races that we think we recognize are the result of sampling error If you survey the totality of global human variation many populations are difficult to classify and the variation we see is actually clinally distributed 5Most biological variation exists within human populations not between them Reason 1 It is difficultimpossible to draw geographic boundaries between human groups 0Humans are masters of dispersal always willing to exchange genes with each other Reason 2 traits are clinally distributed 0Cline change in frequency of a trait usually continuous related to geographic distance or environmental variation 0Clines are often discordant racial traits do not covary Actual Variation within and between Populations OVariation is actually continuous in most traits of interest to those studying race height weight skin color cranial shape ODifferent traits lead to different groupings 0Why a focus on skin color head shape hair color and other racial traits Why not lactose tolerance sickle cell trait height or something else Reason 3 How Many Races are there Anyway 01f races are real entities why are they so hard to define OExisting classifications include anywhere between 3 the usual Caucasoid Negroid Mongoloid and over 60 races Reason 4 Races as We Recognize them are a Product of Sampling Error 01n the US the majority of the population comes from peripheries of the human range where differences are the most extreme 0Examination of the entirety of the human diversity reveals that variation is continuous Reason 5 Most Variation Exists within Populations not Between Them OIndividual human populations even the most geographically isolated typically exhibit 85 more of the total genetic variation in humans at any give locus 0Africans are far more genetically diverse than peoples on any other continent Fallacy of Race OCharacterizes human variation as discontinuous when it is continuous 0Con ates biological and nonbiological characters OIs race a poisoned term A Modern Anthropology of Human Variation OTerm race has political and historical baggage and isn39t helpful for understanding human variation OSherwood Washburn The New Physical Anthropology and others argued that populations are the basic unit of human diversity and adaptation OFrank Livingstone On the nonexistence of human races static typological notions of race are incompatible with dynamic concepts of natural selection OSuggests focus on geographic variation in single traits clinal variation and on adaptive dimensions of human variation Human Skeletal Variation Applied Skeletal Analysis 0Let39s say a construction crew discovers a human skeleton while putting in a bridge OWork halts and the anthropologists are called in 0What do you do now What are your goals Goals of Applied Skeletal Analysis OIn a human context an activity beyond taxonomy identification of species 0The identification of individual traits in skeletal remains 0The reconstruction of individual biology and behavior based on clues in skeletal remains 0Used in forensic and archaeological contexts Forensic Anthropology 0Constructs biological profiles from skeletal remains age sex height population origin OAnalyzes trauma to bone to determine both antemortem and postmortem damage OIs usually conducted in dark dusty basements TV dramas notwithstanding Bioarchaeology and Paleoanthropology 0Study of skeletal remains to obtain basic biological information OBioarchaeology context of archaeological sites focused on study of human behaviorculture OPaleoanthropology context of fossil sites study of ancient humans and human ancestors Applied Skeletal Analysis OSame general goals whether applied to modem or archaic humans OIn modern humans goal is usually to positively identify the individual Reconstructing Biological Profiles ORequires knowledge of human skeleton and variation within and between populations 0Not an easy task estimation vs determination 0Based on skeletal collections with independentlyobtained information Biological Profiles OSeX age ancestry stature etc OApplies knowledge of human biological variation in order to learn about an unknown set of human remains 0seX determination Oancestry Otrauma Oage determination 0body size 0anomalies and pathologies Causes of Skeletal Variation OChronological vs physiological age OVariation related to genetics OVariation related to lifestyle or individual history ex incisal shoveling most common in East AsianNative American Variation Related to Lifestyle or Individual History OBone as living tissue use and disuse OIndividual anomalies occupation number of births nutrition disease etc OTrauma to bone type and timing ante or postmortem Bone as a Living Tissue 0Composite of organic primarily the protein collagen and inorganic primarily hydroxyapatite calcium phosphate components 0Constant turnover 0responds to stress Olaid down where needed and resorbed where not needed 00steoblasts deposit b build bone 00steoclasts break it down Wolff s Law and Professional Tennis Players OAsymmetry in professional tennis players bone densitycontent and muscle mass about 20 higher in dominant arm Neandertal Limb Asymmetry 0Churchill and Schmitt note that the upper limbs of Neandertals often show asymmetric development 0The patterns of muscle development re ect spear thrusting not throwing to kill prey Long Bone Anatomy and Growth OMammilian long bone growth is unique 0Growth in length occurs at the metaphyses growth plates not at the ends of the bone OEpiphysis end OMetaphysis growth plate ODiaphysis shaft OMedullary cavity 0Foramen hole OFacet OTubercleTuberosity Sexual Dimorphism OFemales average 92 of the size of males ODifferences more pronounced in adults OMany sex differences are sizerelated robusticity and linear dimensions ORe ects genetic and environmental factors OVariation within and between populations OSusceptible to secular changes diet and activity shifts NonSize Related Differences OPelvis is the best indicator of sex accuracy of identification 95 OShape OPelvic inlet OPubic shape OSubpubic angle 0Sciatic notch Sacrum 0Size and robusticity larger in women Four Key Diagnostic Features of the Pelvis OVentral arc OSubpubic concavity OMedial aspect of ischiopubic ramus 0Sciatic notch OPhenice Method includes s 13 and is accurate approximately 96100 of the time 0The greater sciatic notch is wider in females than males 60 degrees vs 30 degrees 0Notch is more asymmetrical in males than in females Sexual Dimorphism of the Skull ODifferences primarily re ect differences in body size OSizedevelopment of muscle attachments 0Size of mastoid process base of skull OSharpness of orbital margin brow ridge angle 0Size of brow ridges 0Shape of chin mental eminence 0Shape of forehead OAngle are and exure of mandible Estimates of Body Size 0Most estimates of body size from the skeleton focus on height OWeight can be estimated but estimates are usually inaccurate OArticular surface and weight may be estimated at 18 years 0Cross section indicates recent weight OHeight stature typically estimated from long bones or fragment of long bones 0Estimates based on multiple bones are more accurate Age Determination in Subadults 0Appearance of ossification centers in neonates and infants 0Growth of bones in size OEpiphyseal fusion ODental eruption OEstimates were typically fairly precise when lt18 years Appearance and Development of Ossification Centers OAll primary growth centers are present at birth OSecondary centers appear in infancy and childhood 0Most epiphyses are cartilage at birth first bone appears in late fetal period 011th week gestation 806 centers birth 450 centers adult 206 bones OOssification centers unite in a predictable sequence that allows age estimation Development of the Skull OFontanelles soft spots allow passage of large infant skull through birth canal 0Fontanelles disappear during the first two years of life OCranial sutures joints between cranial bones fuse later in a predictable order and are used in skeletal aging of subadults and adults OFetal long bone measurements can be used to estimate body length and therefore gestational age Timing of Skeletal Development 0Fusion of secondary centers epiphyseal fusion is a key method of skeletal age determination OOn femur shaft and epiphyses are completely separate at birth but are connected by age 18 Timing of Epiphyseal Fusion OSequence stable but timing variable 0Sex differences l2 years earlier in females 0Some fuse early 12l4 years elbow proximal radius and ulna distal humerus 0Most fusion ends in the early 20s OMedial clavicle is usually the last epiphysis to fuse can be as late as 2530 years old 0Age of fusion for skeletal elements in US military casualties during the Korean War shows considerable variation in age of fusion Skeletal Changes in Adulthood OAging based on the skeleton becomes more difficult in adults especially in isolated specimens 0Some late fusing epiphyses early 20s OAging primarily relies on degenerative changes and is most accurate in skeletal series OLarger range for estimates are typical 3040 years OPubic symphysis and sternal ends of ribs are best ODivergence of chronologicalphysiological age confounds estimation Dental Formation and Eruption 0Formation and eruption of deciduous and permanent definition OEruption appearance of tooth at gum radiographs are used to visualize unerupted teeth 0Sequence of eruption is constant variation in eruption timing between individuals and populations 0The most accurate age estimation technique from birth to 1012 years of age Deciduous Teeth 0Formation of all deciduous teeth begins by end of sixth fetal month OFirst tooth erupts at 68 months typically lower central incisors last erupts by 23 years OSecond molars are last to erupt Skeletal Pathology ORe ects the effects of disease on the skeleton OIncludes evidence of nutritional deficiencies infectious disease and congenital disorders pelvis With rickets sacrum With spina bifida Skeletal Anomalies OSkeletal form that is atypical or unusual but results in no negative effects or functional differences ORe ects changes to the skeleton re ecting events and activities of daily life Trauma 0What caused a particular trauma and When it occurred OPre or antemortem OPerimortem 0Postmortem Estimates of Ancestry in Forensic Anthropology OAssignment to race categories that would re ect selfidentificaton or identification by others OPrimarily based on the skull OTwo approaches nonmetric and metric measurements ONo simple divisions between categories but continuous gradations OLike estimates of age or stature race identifications are probability statements OAccuracy 8090 in adults in certain contexts Nonmetric Features OIdeally not subject to environmental variation 0Based on frequency distributions of various traits in different populations lots of overlap remember traits vary clinally 0Most traits are only relevant in adults exceptions are in dentition Orbital Shape 0Round common in Asians ORectangular common in Africans 0Sloping common in Europeans Nasal Opening OIntermediate Asian OWide African ONarrow and elongated European Zygomatic Projection Cheekbones OEuropeans small and retreating OAsianNative American robust and aring high cheekbones PalateDental Arcade Shape OParabolic common in Europeans OEllipticalrounded common in AsiansNative Americans OHyperbolic common in Africans Chin Shape OBlunt typical in AsianNative American OSquared bilobate projecting especially in males European 0Round and retreating African Metric Techniques OExtremely objective but have major limitations OGiles amp Elliot 1962 ODerived using the Terry HamannTodd and prehistoric Native American skeletal collections 0Uses 8 cranial measurements ODifferentiates white vs black and white vs native American Problems with Metric Techniques 0Don39t consider admixture OAbrupt transition between races does not conform to reality 0Based on older collections of limited diversity 0Uses prehistoric Native Americans but what about variation 0Doesn39t work well outside of collections Forensic Database of Modern Cases OFORDISC v20 06 populations African Chinese Vietnamese Hispanic Native American and European OSkull measurements 24 cranial and 10 mandibular 0Posterior probabilities OTypical probabilities Human Evolutionary Biology Human Evolutionary Biology Today OHuman adaptation and adaptability OEvolutionary issues that are special or unique to humans 0The study of human evolutionary biology Genotype Phenotype and the Concept of Race 0Social dimensions of the race concept OHow race becomes biology OHealth disparities Evolutionary Biology Issues Special or Unique to Humans OEvolutionary theory as the primary explanatory framework for understanding human biological variation and change over time 0Forces of evolution natural selection mutation gene ow genetic drift OStudies tend to focus on adaptation Difficulties Specific to the Study of Human Evolutionary Biology OResistance by some 0Difficult to assess evolution because of long generation time OLab studies limited for ethical practical and theoretical reasons OEXpensive OExtent of human ability to modify environment 0Layers of adaptation 0Complex interplay of biology and behavior 0Aspects of culture can be adaptive and allow survival also culture as stressor OHuman ability to biologically adjust during lifetime functional adaptation acclimatization Documenting Human Evolutionary Changes 0Difficult to measure evolutionary changes in humans because of long lifespan OSome studies have assessed differential fertility and mortality OSickle cell allele carriers have the highest fitness survival in malarial regions Livingstone OYanomamo men who have killed other men have more wives and a greater number of offspring Caveats in Human Evolutionary Biology 0Most studies rely on proxies for measuring fitnessadaptive success such as health growth or work occupancy ORecall what is the definition of fitness in an evolutionary context 0Difficult to establish causality vs correlation Evolutionary Explanations of Human Variation 0Very difficult to identify causality 0Most studies rely on associations correlations correlation does not equal causation Oexample body sizeproportions and climate Orelative sitting height is negatively correlated with mean annual temperature does this equal cause OCausality is difficult to infer Human Adaptation and Adaptability 0 Adaptation is often used in a general sense to refer to changes by which organisms surmount challenges to life OIn humans includes culturalbehavior adaptation Levels of Biological Adaptation OGenetic or Darwinian adaptation OFunctional adaptation Genetic or Darwinian Adaptation OGenetic or Darwinian adaptation develops over many generations re ects response to natural selection OMeasured through differential fertility and mortality OSome probably examples in humans skin color sickle cell trait body size and proportions differences in basal metabolic rate OAmong modern humans genetic change is expected to be adaptation of last resort 0Takes a long time and environmental conditions may change rapidly OReduces longterm exibility by canalizing variation OGenetic adaptation is expected when environmental stressors are present over a long period or the stressor can39t be buffered using other means culture or behavior Functional Adaptations Adaptability OAdjustments during the life of an individual to help maintain homeostasis in response to a stressor 0Homeostasis maintenance of the internal physiological environment within tolerable limits OStressor stress any factor that interferes with homeostasis physical cold heat hypoxia or psychological Acclimatization OAcclimatization shortterm reversible 0development of enhanced sweating ability in hot climates Otanning in response to solar radiation Oincreased RBC and hemoglobin production at high altitude ODevelopmental acclimatization Developmental Plasticity longterm irreversible changes that result from exposure to environmental stressors during growth and development Olarge lung volume at high altitude 0 fetal programming 0age at menarche and height Genotype Phenotype and the Concept of Race OHumans can39t be divided into natural biological units according to the concept of race 0The term race is problematic for several reasons biologically inaccurate not useful for classification or understanding loaded and has historical baggage oHowever this does not mean the human biological variation does not exist not does it deny the social reality of race Race as a Sociocultural Phenomenon ORace as a worldview a culturally structured way of perceiving and interpreting reality OSocial race a group assumed to have a biological basis but actually perceived and defined in a social context by a particular culture rather than by scientific criteria Public Perceptions of Race OPublic conception is that races are discrete permanent and relatively homogeneous OCultural variation in how race is classified American approach is not the only system 00ften used synonymous with the term ethnic group group defined by cultural similarities Health Disparities and Race ORace as a sociocultural phenomenon that has force in people39s lives one with biological consequences OHeath disparities as a window onto race Health Disparities in the US OSubstantial inequalities between racially defined groups for all major causes of morbidity and mortality 0cardiovascular disease and diabetes 0cancer Oinfections Olow birth weight and preterm delivery 0Burden of poor health especially high in African Americans Cageadjusted death rate for blacks gt30 higher than whites Problems with the Race Concept in Medicine 0 If race is not biologywhy are there such clear differences among racially defined groups in a range of biological phenomena Gravlee 2009 0Race is often used uncritically as a major category in biomedical science and public health 0used as proxy for environmental behavioral and genetic factors 0however the typical assumption is that racial differences are explained by genetic factors Biology Not Genetics OAn over focus on genetic causes Hypertension risk OBiocultural approach to understand how race becomes biology 0Need to consider multiple levels of analysis and a developmental and lifecourse perspective OCategorization by social race can affect treatment of others and opportunities which can affect biology Health Effects of Racism OIndividual level effects of racism discrimination in medical care 0experimental studies with actors have shown that black parents especially women are much less likely to be referred for treatment than white patients even when describing identical symptoms 0discrimination linked to chronic psychosocial stress which is linked to various chronic diseases OInstitutionalized racism 0more limited opportunities and reduced social mobility environmental racism 0can have intergenerational effects that aren39t genetic low birth weight effects on adult health Multigenerational Effects OIntergenerational effects that are not genetic effects of discrimination related to chronic disease that lead to effects on fetal environment that lead to effects on adult chronic disease risk fetal programming Understanding Genetic Differences 0There are genetic differences between major continental groups but these are relatively minor most are in noncoding DNA with little if any effects on disease 0Most but not all alleles associated with complex diseases are ancient and shared across populations OMost variation within populations OCertain genetic diseases vary markedly among populations but these conditions are generally rare TaySachs cystic fibrosis sickle cell anemia 0Categories of interest are smaller populations Beyond Black VS White 0Based on work of Murray et al 2006 ODivided US into distinct subgroups based on sociodemographic and geographic indicators census defined race location etc the Eight Americas OHealthy Americans are very healthy unhealthy Americans are very unhealthy OEnormous range 0Native American men in Washabaugh County South Dakota life expectancy of 58 years to Asian women in Bergen County New Jersey life expectancy of 91 years 0These health disparities enormous by international standards Health Disparities Among Whites OWide variation in white Americans with relatively high life expectancy in rural white from the Midwest America 2 compared to whites from Appalachia America 4 0 gap of 4 years in life expectancy but similar income levels and both groups are poor compared to other whites 0Take home message income is important but it isn39t everything The 8 Americas A Search for Causes OHealth disparities largest for young and middleaged adults OBiggest disparities are in chronic diseases and injuries OHealth disparities haven39t changed substantially between 1982 and 2001 Causes of Health Disparities 0Genetic factors have limited explanatory power 0Access to medical care and discrimination in medical care OHealthrelated behaviors alcohol and tobacco use 0Access to high quality foods 0Effects of early life environmental conditions OChronic psychosocial stress Stress and Health ODirect physiological effects through activation of stress response and indirect effects through health related behaviors diet smoking sleep OSome key factors Opercieved lack of control Olifestyle incongruity aspirations gt resources Ominimal information on duration and intensity of stressors Olack of social support 0inability to achieve full social engagement and participation OIncome distribution in the US is the most unequal of developed nations 040 of wealth controlled by 1 of population increasing with decreased social mobility 0increased levels of chronic psychosocial stress Human Genetic Variation Pollard 2009 0Most mutations are neutral mutations that lead to neutral rates of change over time OPositive selection leads to accelerated change 0Conversely ongoing selection can lead to a total lack of change stabilizing selection on loci that are functionally important cytochrome C 0Assumption that the sequences that shaped humankind underwent positive selection or that adaptation was more important than stochastic forces in human evolution OHARl 118 base pairs OEntire human genome 3 billion base pairs OHARl 00000000039 of the human genome OMany areas of interest in the human genome do not code for proteins Genetic Terminology OGenes sections of DNA with identifiable structure andor function 0 A general term meaning loosely the physical entity transmitted from parent to offspring during the reproductive process that in uences hereditary traits 0The average gene is about 3000 bases long but huge variation in length OEach somatic cell nucleus contains 46 chromosomes 23 pairs OEach chromosome contains 50000 to 100000 genes Genes VS Alleles OAlleles alternative forms of a gene that produce different phenotypes OEX a gene codes for coat color and alternative forms may yield black red etc 00ften when we use the word gene we really mean allele 0gene is to allele as soda is to pepsicokesprite Genotype VS Phenotype OMelanocortin 1 MC1R locus in dogs OTwo alleles B and b 0B black allele dominant 0b red allele recessive OPhenotypes red or black coat OGenotypes BB or BB and bb Gene Loci 0Locus physical location of a gene on a chromosome plural loci 0p shorter arm q longer arm OHuntington39s locus 4p163 short arm of chromosome 4 in the 1st region 6th band in the 1st region and 3rd subband of the 6th band Human Genes 0Humans have 32 billion base pairs and 25 000 genes OFunction remains unknown for gt50 of genes 0Locations appear to be random no logical pattern Types of Genes OStructural genes coding sequences code for proteins which are constructed from amino acids ex collagen enzymes and hormones ORegulatory genes DNA sequences in regulatory genes determine when structural genes are expressed ex HOX genes highly conserved group of genes that control segmental patterns during ontogeny DNA ODeoxyribnucleic acid 0The genetic code carries instructions for building an organism and keeping it functional 0Transcription and translation of the code builds amino acids and in turn proteins 0 Baclltbones sugars and phosphates 0 Rungs nitrogenous base pairs ONucleotide base sugarphosphate group 0Four types of bases and they always pair specifically OPurines adenine and guanine OPyrimidines cytosine and thymine OAdenine with thymine AT OGuanine with cytosine GC NonCoding DNA OMost DNA is noncoding only 2 of the human genome contains genes that code for proteins ORepeated noncoding sequences at least 50 of genome in humans high compared to other species OOnly DNA that affects phenotype is subject to natural selection 0Noncoding DNA can be within or between genes 0Exons are coding DNA that is transcribed during protein synthesis but most of the nucleotide sequences in genes are not expressed some noncoding sequences called introns are initially transcribed but then are clipped out Mitochondrial DNA mtDNA ODNA found in the mitochondria not the nucleus OOnly 16000 base pairs vs billions in nDNA 0Codes for 13 proteins 0Two major noncoding regions OMaternally inherited transmitted from mother only to children OHigh mutation rate compared to nuclear DNA since much is noncoding OHigh copy number in each cell lots of redundancy Mutations 0Result from mistakes that occur during DNA replication OMutations raw material that introduces genetic variation within populations Types of Mutations OPoint mutations change in a single base pair of DNA substitutions can be a silent mutation OFrameshift insertion or deletion of DNA that leads to misreading codons OMitosis creates all cells except sex cells OMeiosis creates only sex cells Nondisjuction Errors 0Nondisjunction lack of separation between homologous chromosomes during meiosis when combined with a normal gamete leads to an extra chromosome 3 vs 2 0Trisomy21 Down39s syndrome autosomal OXXY Klinefelter39s syndrome sex chromosomes Single Gene Inheritance Mendelian Traits OTraits with different and nonoverlappingdiscontinuous phenotypic variants qualitative not quantitative variation Oearlobe form freehanging dominant attached recessive 0PTC tasting taster dominant nontaster recessive OPleiotropy single gene with multiple effects on phenotype Multi gene Inheritance Poygenic Traits 0Expression depends on the action of multiple genes each of which may have more than one allele 00ften produce continuous variation quantitative variation OEnVironment often in uences expression of trait 0Height and most other anthropometric dimensions skin color etc fall into this category OMeasuring Contributions of Genetic Factors to the Expression of Polygenic Traits ORelative contributions of genes and enVironment to the phenotype can be estimated OHeritability proportion of total phenotypic variability for a trait ascribed to genetic factors 0Ranges from 0 to 1 0 only enVironment 1 only genetics 0Difficult to estimate in human populations can use twin studies or adoption studies but sample sizes small OHeritability variability caused by geneticsvariability caused by genetics variability caused by enVironment Epigenetic Effects 0Differences in gene expression differences in how DNA is read without changes in the DNA itself 0Most epigenetic changes occur in early development fetal life or infancy OSeveral epigenetic mechanisms operate in gene activation and inactivation Ohistones are the main protein component of chromatic the complex of nucleic acids and proteins that condense to form chromosomes during cell diVision and serve as spools around which DNA wraps thereby in uencing regulation of gene expression Classic Genetic Markers OPolymorphism occurrence in a discrete heritable trait of two or more variants alleles or haplotypes within a population at a frequency greater than 1 the opposite of polymorphic is fixed 0Classic markers protein morphisms OMendelian inheritance blood group systems ABO or MN or hemoglobin variants 0Complex of DOIVgenic traits complex quantitative phenotypes Otraits whose properties are controlled by many genes and whose inheritance does not follow the simple rules of Mendelian genetics body size environment may play role in expression 0The seven pea treats studied by Mendel height ower color ower position seed color seed shape pod color pod shape 0DNA sequencing output Modern technologies make it possible to read and analyze sequences of base pairs Modern Genetic Markers 0 ingle nucleotide polymorphisms SNPs 2 polymorphisms that represent single base pair changes via point mutation 0in coding or noncoding regions many with no effect on cell function but some with role in disease or drug metabolism OVariable number tandem repeats VNTRs blocks of repeated base pair sequences present in the human genome Omicrosatellites and minisatellites Otypically neutral in noncoding DNA DNA fingerprinting studies OHa lot es Genes nucleotides or combinations of genes or nucleotides SNPs that are either in close proximity and inherited as a linked unit or are otherwise associated statistically haplogroups are clusters of haplotypes Ancient DNA 0Recovery of DNA nuclear DNA or mtDNA from ancient remains ODNA typically degrades relatively rapidly especially in warm humid environments mtDNA better but still not great 0Contamination is a major concern in ancient DNA studies Ancient DNA Analyses OIn part made possible by polymerase chain reaction PCR technology which makes many copies of a particular DNA segment with high specificity OAncient mtDNA and nDNA recovered from Neandertals 70000 40000 yrs old Difficulties of Neandertal Genomics 0Risk of contamination by modern human DNA OAgerelated decay of DNA OAvailable sequence is very fragmented and contains errors Mapping Genomes 0Human Genome Project HGP 0started in 1990 based on 510 individuals 0 goal to identify all genes and create reference sequence 0a highquality finished sequence of the human genome was completed in 2003 current assembly is from 2009 00ther primates chimpazee 2005 rhesus macaque 2006 orangutan 2007 common marmoset 2009 ONeandertal genome announced Feb 2009 63 of nucleotides sequenced from 3 Croatian Neandertal fossils Understanding Human Genetic Diversity OIdentification and characterization of genetic diversity in populations 0What makes us morphologically and behaviorally unique 0Why are some people at greater risk for disease and respond differently to drug treatments Current Mapping Projects OInternational HapMap Proiect 0focused on small number of people in four populations Yoruba Japan China and European Americans 0 goal is to identify and catalog genetic variation to find genes that affect disease and response to therapeutic drugs OSNP Consortium 0UK based project that started in 1999 with the aim to map common SNPs Omapped 18 million total SNPs and now focused on population variation Opublic database availably dbSNP 0Human Genome Diversity Project 0began in 1990s and focused on DNA that varies between populations 0focused on small indigenous groups gt50 sampled Gen02raphic Proiect 0privately funded collaboration between National Geographic and IBM that shares researchers with HGDP 0seeks to understand geographical patterns of genetic variation and reconstruct patterns of human evolution and migration What Makes us Human ORecent comparative genomic studies of human vs chimps and other mammals to locate regions of change 0We are 99 identical to chimps but 1 15 million bases different OSmall changes have big effects ex in regulatory genes Uniquely Human DNA OIdentification of regions of interest including several related to brain developmentfunction HARl and FOXP2 OSome regions show change but vary in human populations LCT and AMYl 0This is preliminary research much unknown 0Many of the differences are not in coding regions junk DNA may not be all junk ORegulatory sequences that turn genes on or off Evolutionary Forces from a Genetic Perspective OMutation low rate but ultimate source of genetic variation OSelection alleles associated with the more fit genotype overrepresented in the next generation and increase in frequency OGene ow increases genetic diversity within populations and decreases genetic diversity between populations OGenetic drift population size is key decreases genetic variation within populations and increases genetic variation between populations examples fixation vs extinction Evidence for Recent and Ongoing Selection OEvidence circumstantial for extensive recent lt10000 years and potentially ongoing selection in man populations around the world Omalaria resistance 0resistance to Lassa fever virus Olactase gene 0alcohol metabolism Oskin pigmentation 0type 2 diabetes susceptibility 0At least 7 of human genes may have undergone evolution within the past 5000 years 0Rate of evolution appears to have accelerated within the past 40000 and especially 10000 years Human Genetic Variation and the Concept of Race 0Humans are genetically extremely homogenous OHumans show low levels of genetic variability relative to common chimpanzees and other hominoids OHuman racial classifications based on different criteria are not concordant Evolutionary Convergence ODistantly related populations are similar for certain traits if they evolved under the same selective pressure not indicative of genetic distance OSkin color phenoypes in subSaharan Africa southern India Australia and Melanesia cluster together 0 ngmy groups in West Africa and Southeast Asia exhibit convergent evolution in morphology body size African Genetic Markers in Brazilians of Different Races 0Comparison of an index of African ancestry for contemporary Africans living on Sao Tome Island contemporary Portuguese and contemporary Brazilians classified as black white or intermediate based on skin color facial morphology and hair texture OThus Brazilian racial classification predicts little about overall genetic similarity Patterning of Genetic Variation OMost variation is within populations OLewontin 1972 based on classical markers including blood groups and other proteins and numerous other studies using classical markers DNA sequencing insertiondeletions and microsatellites 010 of variation is found between races 05 of variation is found between populations within regions 085 of variation is found within populations 0People tend to be more genetically and phenotypically similar to people who live near them than to people who live farther away 0 Isolation by Distance high gene ow between geographically close populations OHuman genetic diversity forms geographic clines no major genetic discontinuities between different continents or races OExtensive genetic sharing across continents the rule not the exception OCertain contexts the US with massive recent mixing can cloud our perspective on global genetic variation OLong human history of gene ow between populations which has recently accelerated Summary 0Humans are extremely homogenous genetically due to recent origin in Africa and rapid population expansion and dispersal OHumans exhibit probable adaptations to an extensive range of environments by genetic means but also culturalbehavioral adaptations and physiological acclimatizations OHuman genetic variation is not compatible with race concept OMost variation between populations not natural subdivisions into biologically distinct groups and lots of admixture OStill differences exist in both genotype and phenotype within and between human populations 0and social race categories have important effects on biology Personal Genomics Ancestry VS Race OAndrew Pollack Mapping a Human Genome via an eBay Auction OIn a few years it will only cost 1000 to determine the sequence of virtually all 6 billion chemical units of DNA in a person39s 46 chromosomes scientists say 0ANCESTRYbyDNA25 panchromosomal assay for genetic ancestry infers genetic ancestry or heritage 0EURODNA10 measures European subancestry Seeking Ancestry in DNA Ties Uncovered by Tests OAmy Harmon OBasis Accuracy Status as an underrepresented minority OWhat defines Native American Status OShould ancestry define rights to property
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