Intro to Anthropology 4 subfields 1.Cultural Anthropology: study of the culture of present day societies (often in non western settings) -ethnography: collection of qualitative data about beliefs,values and social behaviors **interviewing, observing, participating and surveying** 2. Archeology:study of past human societies,usually through “artifacts” -culturalDon't forget about the age old question of math 431
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anthropologists from the past -why people behaved as they did 3.Linguistic Anthropologist: study of the construction and use of language **structure,evolution,social and cultural context** 4.Physical/Biological Anthropologist:study of past and present 1. Human biological evolution 2. Human biocultural variation Human Bio Evolution: study of the changes and physical intellectual traits sense divergence of humans and apes Mixing and Matching the 4 subfields -overlap between the 4 -Bioarchaeology: involves excavation and biological analysis of remains -forensics Human biocultural variation Biocultural Concept: you are a product of your genes AND environment(physical climate,physical activity,diet,stress,any cultural or social factors that influence these) Your Genes are Not your Culture Events during our life influence many aspects of our bodies and minds. These are not predetermined by a person's genes, ancestry, or geographic origin. **Early on scientists thought ancestry determined everything** Great Chain of Being Minerals - plants - animals - humanity - angels - god -internal hierarchy of people based on sex and social status -nearly possible to change one's position Unilineal Evolution: idea that all cultures naturally pass through stages of increasingly complex culture -a group technology and social organization was thought to be determined by their “stage” of cultural evolutionFranz Boas -father of american anthropology -phD in physics -promoted the 4 field approach -jewish immigrant from germany (1858-1942) took cranial measurements in 18,000 immigrant families **parents born in europe had smaller heads **children born in US had larger different shaped heads -heavy influence of nutrients and stress on brain size -ancestry couldn't completely explain the variation in head size *genes don’t determine everything* Boas work lead physical anthropologists to adopt the biocultural perspective -perspective is still emphasized in physical anthro today Culture is Learned and Shared Culture in not fully formed at birth according to genes ancestry or race -you learn how to behave and what to think through your experiences and interactions Biocultural review Human variation is influenced by: inherited genes from our evolutionary past and environmental circumstances, including learned and shared culture Anthropology is holistic (multidisciplinary) -helps scholars understand who humans are ando how they became that way We need the biocultural concept because it provides the best explanation for human behavior What do Physical Anthropologists do? 1.Primatology: study of non human primates **our closest living relatives** 2.Paleoanthropology: study of the fossil record of non human primates and humans 3.Human Biology: study of growth and development and adaptation to environment -genetics 4.Skeletal Bio and Osteology: macroscopic study of the form and function of the human skeleton -microscopic study of bone structure,growth,pathology and strength 5.Forensic Anthro: help to identify features or identities of skeletons found in : Criminal cases, military conflicts, mass disasters(9/11), humans rights violations(mass graves) 6.Bioarcheology: examine population health and demographic of past peoples Introduction to the Scientific Method Observation- define problem - propose hypothesis - gather evidence -test hypothesis - reject/retain hypothesis- develop theory Data= evidence that helps answer questions, solve problems, fills in the gaps in scientific knowledge **data different in 4 subfields**Theory vs Law Theory:an explanation for a phenomena Law:a generalization about a principle or pattern in nature; description of a phenomena From Observation to Hypothesis Hypothesis: a testable prediction that might describe (law) or explain a phenomena(theory) **explain observations,can predict future results, can be refuted by new evidence** History of Evolutionary Theory evolution= Darwin: biological change over multiple generations Modern scientist: genetic change over multiple generations **Evolution is an observation(fact) about the natural world** What is evolutionary thought? Theories explain the process of this biological change -they dont ask whether evolution occurs (it occurs it's a fact) Rather theories explain how evolution occurs (In other words theories provide the mechanism of biological change) Middle Ages: belief in a young static earth Archbishop James Usher 1.calculated a creation date of sunday oct 23 4004 B.C 2.all creatures were unchanging and immutable 3.did not change from original created form 4.had a set place in the great chain of being How do we observe biological Change? 1.is the earth old enough? Bedrock of the earth made of layers deposited by water (sediment) -thought to occur during a one time worldwide flood -fossils were animals that drowned in the flood George-Louis Leclerc, Comte de buffon French Naturalist and writer Studied physical laws about the heating and cooling of earth sized objects Said the earth started as molten rock and needed time to cool down -calculated age of earth at b/w 75,000 and 2-3 million James hutton Rock cycle-surface that is not static, but is constantly eroded, compressed and volcanically deposited at a slow pace -requires millions of years for rock layers to build upCharles Lyel (1797-1876) -Sea levels changes -giant volcanoes on top of old rock -erosion forming valleys Uniformitarianism: earth is changed by natural processes operating both today and in the past -charles applied this to principles of geology 2 Do species change over time? At the time most scientist thought that fossils were chance rock shapes or had fallen from the sky Nicos steno- dissected a giant shark Tongue stones-fossil shark teeth replaced by minerals Robert Hooke Fossil wood and living wood have identical structure -fossil: remains of organisms,formed by the replacement of organic with inorganic material Fossil animals have gone extinct Georges cuvier -elephant fossils in paris distinct from africa,asia, siberian mammoths Persian elephants- extinct species What causes extinction? George cuvier thought that extinction resulted from a catastrophe (volcanoes,earthquakes,floods) Catastrophism- most extinction actually occurs due to forces of evolution rather than violent geological events 3 Do different species have a common origin? John ray searched for a divine organization of species -grouped species based on several features Previously:one feature or organ Species: ultimate unit of taxonomy Cavous Linnaeus Domain(domain-eukarya-bacteria-archaea)-kingdom-phylum-class-order-family-genus Species Chevalier De Lamarck Lamerikarian inheritance of acquired characteristics (actions during life cause new traits in the body) These traits are then passed to offspring (new traits caused by desire to chnage)Problems with inheritance of acquired characteristics 1.not seem in real life (body building and ear cropping on dogs) 2.DNA in sperm and egg not changed Inheritance of Acquired Characteristics -lysenkoism -soviet union Darwin + Natural Selection Review 1.earth is old enough to change:uniformitarionsims 2.species have changed: fossils Charles Darwin Medical school: university of edinburgh, scotland -natural history:cambridge university,england *naturalist to the HMS beagle Background Vocab Species: a group of interbreeding organisms that produce fertile viable offspring Habitat: the specific natural environment in which an organism lives Endemic: only found in 1 location in the world Darwins 2 discoveries -variation in habitat: variation in physical traits Similar species in different locations seem to have a common ancestor The Galapagos island: Mockingbird -similar to south american species, chilean mockingbird (species varied between islands) Adaptive radiation-one ancestor species diverges over many years into multiple species Finches ** morphological variation related to the habitat of the animal** The equation for Darwin's Theory of Evolution +variation +heritability +selection Variation Exists Some variations work better in a given environment (helps them survive or reproduce) Some variations are inherited ( inherited trait in parent appeared in child) Artificial selection: humans select certain kind sof organisms to breed -humans don't create the traits they want in an organism out of thin air, they oick individuals w/t the desired traits to mate Selective breeding of traits by humans =change overtimeDarwin asked: Do Traits become more common in a population b/c something in nature is selecting them Selection: not all individuals can survive to reproduce Thomas Malthus -An essay on the principle of population -population growth is exponential -food supply increase is linear People who get supply and resources will reproduce **For most organisms parents produce multiple offspring, not all survive to reproduce and compete for limited food supply** ---Galapagos: some varieties of traits help food gathering survival and reproduction The equation for natural selection 1.variation:some traits variants increase chance for survival or reproduction 2.heritability: traits are inherited by offspring 3.selection:more individuals are born than can survive to reproduce and result in competition for resources + those that win the competition for survival Differential reproduction : a trait variant helps a parent survive and reproduce *more of the next generation carry that particular trait *variants that help survival or reproduction become more frequent in population Putting it Together Natural selection: process by which some organisms with adaptations preferentially survive and reproduce These adaptations increase in frequency in the population Adaptation: a beneficial variation 1.frequency in population must increase overtime 2.provides two benefits in a certain environment Fitness :number of offspring from a parent with a given trait variant relative to the average # of offspring in the population -Adaptations spread because they increase a parent's fitness offspring Sexual Selection :a species case of natural selection *a trait is appealing to opposite sex and with the trait has increase in mating Males defeat or scare away other malesSexual Selection: female choice Females have more to lose than males when mating Females will be choosy and will pick the male with the best gene,childcare,protection and food production Females choose males that have physical signals of good quality genes Alfred russel wallace Independently developed the theory of evolution via natural selection -him and darwin jointly published their work on natural selection Biological Basis of Life How are traits inherited? Before modern genetics scientist advocated for blending inheritance: gemmules mix together in child child to live a blend of parents Gregor Mendel -monk in the czech republic -observed greater physical traits of pea plants -discrete physical unit response for each trait -now know as a gene for that trait -passed from parent to offspring(obeys mathematical laws for inheritance) -different versions of the same trait didn't blend together in offspring **one variant was dominant and appeared in 1st generation **other trait was recessive and didn't appear until next generation Vocab Gene:sequence of DNA that codes for somthing **found on chromosomes** Allele: alternate versions of a gene **each individual has 2 alleles per gene(2 copies of the gene) Dominant: expressed alle Recessive: not expressed, or masked in present od dominant allele *dominant isn't always most common Darwin's Ideas + Mendel's Ideas= the modern synthesis -evolution:change in allele frequency over time Cells & DNA -chromosomes are made of DNA -nucleus of each human cell contains about 6 ft of DNA together all the chromosomes make up one's genome Types of Cells -prokaryotes (bacteria and archaea) 1.no internal membrane-bound organeless/compartments2.single-celled bacteria & archaea 3.nucleoid region: area where circular chromosome is located Eukaryotes (animals) 1.cells have internal compartments separated by membranes 2.compartments=organelles 3.single celled: yeast 4.multi celled: human 5.nucleus:stores DNA containing majority of your genes 6.mitochondria:converts energy 7 cytoplasm:fluid around organelles Structure of DNA -deoxyribose,sugar,phosphate, and nitrogenous base *basic unit of DNA is a nucleotide -sugar connects to phosphate to make the backbone of DNA -nitrogenous bases face inward (bond together with hydrogen bonds) **bases on one backbone form hydrogen bond with bases on a second backbone** Discovery of DNA structure -rosalind Franklin (used X Ray diffraction to take images of DNA -James WAtson and Francis CRick (published claim DNA was a double helix) 4Types of nitrogenous BAses adenine ,cytosine, guanine and thymine (a-t c-g) Complementary base pairs -G can only appear with C (3 hydrogen bonds) -T can only pair with A (2 hydrogen bonds) DNA replication -occurs in cells nucleus -uses base-pair rules to make a copy of itself sothe cell can divide 1.enzyme breaks hydrogen bonds to separate strand 2.enzyme adds a short primer (sequence of RNA nucleotides) 3.free floting nucleotides added by enzyme *must synthesis from 5 prime to 3 prime** 4.lagging strand is copied in the opposite direction in pieces (okazaki fragments) which are later joined into one strand DNA replication semiconservative -one strand of the new DNA is from the original DNA, and the other strand is made from the newly added nucleotides Where are genes in DNA-a gene is a sequence of the base pairs ona strand of DNA that can make : A protein or a segment of genetic material that will perform a function How do genes become proteins? -proteins are sequences of amino acids -basic structure of a single amino acid -20 types of “R” side chain= 20 amino acid -essential amino acids cannot be made by the human body (this is why we have to consume a variety of different foods in our diet) -sequence of nucleotides defines a gene - used an intermediate made of RNA to convert nucleotides into amino acids - sequence of amino acids defines a protein RNA Ribonucleic acid -uses the base uracil instead of thymine (a-u, c-g) -single stranded -less stable than DNA -contains ribose instead of deoxyribose DNA to Protein 1.Transcription: gene to mRNA -dna separates near the gene or interest Triplet:a group of 3 bases on the DNA strand -complementary RNA bases attaches to make messenger RNA(mRNA) -this is single stranded -mRNA modification **some of the mRNA bases are cut out before it leaves the nuclues (EXon: coding DNA intron-noncoding DNA that is spliced out -mRNA leaves nucleus and moves to cytoplasm , ribosomes (made of mRNA) latches on -3 bases of the mRNA(codon)= one amino acid 1.different mRNA codons respond to the 20 amino acids 2.multiple codons can code for the same amino acid 3.stop codons signal the end of a protein -tRNA matches the correct amino acid to each codon(3 bases of mRNA) on the mRNA -anticodon=the 3 complementary bases that that match the mRNA coden -the other end of the tRNA holds the amino acid that corresponds to the mRNA codon 2.Translation:mRNA to protein -polypeptide=chain of amino acids held together by multiple peptide binds Heredity and Evolution Part1: Chromosome structure and mechanisms of inheritance Gene:a sequence of DNA on a chromosome that makes a molecular product Allele: alternative form of a gene Locus: the location of the allele on a chromosomeKaryotype: complete set of chromosomes 46 individual chromosomes in humans 22 pairs of autosomes (non sex chromosomes) 1 pair of sex chromosomes. xx=female xy=male Genome:nuclear DNA + mitochondrial DNA 23 pairs of chromosomes Each pair -one from father and one from mother “homologous chromosomes” Carry the same genes May have different alleles for those genes For each gene an individual is either homozygous=both alleles are the same heterozygous=two alleles are different Part 2 Which allele is expressed? Genotype: the two alleles that an individual has for a given gene Phenotype: the physical expression of the gene Traits Dominant Trait:one or two copies in the genotype will make the trait expressed in the phenotype **capital letter **expressed in the heterozygote Recessive trait:must have 2 copies in the genotype to be expressed in the phenotype **lowercase letter **masked in the heterozygote Homozygous dominant Homozygous recessive Heterozygous Mathematics of Mendelian Genetics -breeding a homozygous dom parent with a homo rec parent tells us which trait is dominant The dominant trait is the one that shows up in the heter offspring phenotype. Part 3 Mathematics of mendelian genetics Breeding a homozygous dominant parent with a homozygous recessive.Mendel's Law of Independent Assortments: diff traits are inherited independently of one another Green and yellow pea pod are both dominant alleles Discrete traits are not inherited as pairs -ability to taste pcp paper -free or attached earlobes -hitchhiker thumb -hair on back of head -widows peak -cleft in chin Exception to mendel's genetics #1 traits on same chromosome not assort independently Linked Genes: found close together on same chromosome -alleles for these genes are usually inherited together (don't produce expected ratio) #2 Polygenic traits are “continuous” #3 Codominant: heterozygotes express both alleles. Antigens: molecule on the surface of cells that tell your body that the cell belongs to you 3 types of alleles for antigens on RBCs: A B O Allele A produces “type A” antigens Allele B produces “type B” antigens Genotype AA or AO phenotype A antigen #4 Pleiotropy (one gene linked to many traits) Ex.phenylketonuria -body functions that rely on tyrosine are disrupted (melanin-skin pigment) (body growth (mental growth ) **all rely on tyrosine #5 sex linked traits -if an allele is recessive and located on the x chromosome women : xx (must be homozygous recessive to appear on phenotype) Men xy (y chromosome doesn't count for x linked genes) -only needs trait on the x chrom for it to appear in the phenotype #6 heritability Heritability (H^2) genetic variation/ genetic variation + environmental Part 5 regulatory DNA & mitochondrial DNA Coding DNA ( exons) = produce a specific protein **make up the mature mRNA, about 5% of nuclear DNA**Noncoding DNA (introns) = do not produce a specific protein -corresponding sequence is cut out from mRNA -about 80% of noncoding DNA is regulatory -noncoding DNA- micro RNA, which can decrease expression of other genes by binding to the mRNA for those genes (stops it from being translated) MItochondrial DNA (m+ DNA) -only contains 37 genes, while nuclear DNA has 20,000-25,000 genes -sperm's mitochondria do not enter the egg (only the nucleus enters); offspring only have the mothers mito DNA -m+DNA passed down through mother's lineage Part 6: Meiosis and Mitosis Somatic (Body) cells -non-reproductive cells -ex. Skin cells, hair cells, heart cells, etc -not passed to offspring -has fun chromosome # . diploid (2 copies of every chromosome) Somatic cell divisions -Point: 1 cell- 2 cells -Both somatic cells will need all 46 chromosomes (2 sets of 23) -DNA replication: each chromosome copies itself -remains joined at middle with other chromosome Mitosis :somatic cell division Starts with 46 chromosomes (diploid) and ends with 46 -goal:to end with identical daughter cells Gamete :sexual reproduction cell male=sperm female=egg sperm+egg= zygote (offspring) Zygotes are haploid, only have 23 chromosomes 22 autosomes and either 1x chromosome or ly haploid(one copy of every chrom, only half of the DNA) Meiosis :creates gametes -starts with 46 chromosomes (diploid) -meiosis 1: involves duplication of diploid cells -resulting cells are not identical to original -crossing over occursMeiosis 2: no second round of duplication **results in 4 haploid cells**(gametes) Crossing over or recombination -maternal and paternal versions of a given chromosome line up next to each other before separating -for a particular gene , the maternal and paternal version of a chromosome alleles Meiosis increases diversity -maternal and paternal chromosomes can swap alleles for a given gene through crossing over -different combinations of parental genes= differet com Binations of traits in offspring Sperm Gamete 22 autosomes and either 1 x or y chromosome Egg Gamete 22 autosomes and 1 x chromosomes Once sperm fertilizes egg, the zygote will have 46 chromosomes -diploid, 22 automsomes pairs, 1 sex chromosome pair -zygote dividies through mitpsis= every other somatic cell Population genetics part1 Organisms dont evolve, populations do Background vocab Deme: a local group of organisms that have similar genes, interbreed and produce offspring Species: all the poplulation and memebers capable of breeding with each other and providing viable offspring ** groups which can not interbreed are said to be reproductively isolated** Gene pool: all the genetic info in the breeding population Evolution occurs if : -frequency of each allele in the gene pool changes -new alles enter the gene pool -old alleles leave the gene pool Main Ideas of POpulation Genetics 1. All evolution involves gentic gentic mechanisms 2. Evolution is gradual ** small genetic changes accumulate and result in change 3. Natural selection is the main mechanism of evolution ** but other mechanisms exist** 4. Microevolutionary changes explain macro evolutionary changesMicro evolution Small scale evolution; changes in allele frequency from generation to generation Macroevolution Large scale evolution -speciation eveents that occur after many generations -often result in in reproductive isolation Forces of Evolution Why do allele frequencies change in a population 1. Mutation -any heritable change in the strucutre or amount of genetic material -only heritable if the mutation occurs in the DNA of the gametes New alleles=increases genetic variation between populations Mutations are the raw material of evolition What cause mutation 1.induced mutatuions: caused by specific environmental agents caused mutagens CUV light, radiation, some chemicals 2.spontaneous mutations: random mistakes during cell division (mistaes during DNA replication) **enzymes ad wrong base pair** 2. Gene flow or “admixture” -exchange of genetic material (alleles) between 2 or more populations **decreases genetic variation b/w populations** Key determinant: can individual from one pop access mates from another 3.genetic drift Change i allele frequency from one population to the next due to chance events Causes:bottleneck effect: a large portion of the population is eliminated so that only a few individuals remain Founder Effect: a small group of population migrates to a new region and is reproductively isolated 4.Natural selection: Only force that adapts population to its environment Natural s.=not random=variation which are less fit are selected against and eliminated. Population Genetics part 2 Selection for the Heterozygous= the heterozygous advantage Aa-intermediate phenotype with more fitness than either AA or aa A or a survive because they are necessary for the heterozygote Sickle cell anemia :hemoglobin gene:makes hemoglobin -protein that carries oxygen in red blood cells Allele A:normal hg Allele S: abnormal Hb(binds less oxygen) What is sickle cell anemia?Abnormal Hb structure causes red blood cells to become sickle shape -get stuck in capillaries and block blood flow -deliver less Trends **20-30% of people living in equatorial africa have allele s sickle cell high where malaria is present Genotypes for the Hb gene AA can host malaria-death of individual if affected by malaria As produce normal and abnormal hemoglobin -immune to malaria -adequately transports oxygen to tissues ss-80% of all people die before reproductive age -cannot be infected by malaria Ina areas with malaria individuals with as genotype have the highest fitness : they are immune to both sickle cell anemia and and malaria -this keeps s allele in the population even though its harmful in homozygous forms Hardy Weinberg Equilibrium Hypothetical model developed independently by H.W Equilibrium: stable system characterized by no change in allele frequency from generation Assumes: (pinky)small population= no genetic drift (Ring finger) marriage= random mating (no sexual selection) (middle)=no mutation (pointer)=individual move=no gene flow (thumb)s up=no natural selection **this state can never realistically exist in a population** **when the population is not in equilibrium that means that the population is evolving** Calculating Allele Frequencies Dominant allele frequency=p Recessive allele frequency=q p+q=1 **use to solve for unknown** Another way: p=total# of dominant alleles/ total # of alleles q=total # of recessive alleles/ total # of alleles Calculating Genotype Frequencies Homozygous dominant: pxp=p^2 Homozygous recessive: qxq=q^2 Heterozygous: pq+pq=2pqp^2 + 2pq +q^2 = 1 When solving these values are the expected values and you need to compare to the actual values observed in nature. Maten=equilibrium,no evolution No match= evolution is occurring because allele frequencies changed Example Sickle cell anemia p=dominant=normal allele A q=recessive allele s Given 4% of population is born worn sickle cell anemia (homozygous recessive) Goal: find the 3 geno frequencies What is Variation? Differences between people (within a population)(bw populations) Human variation can be 1.genetic variation 2.phenotypic variation **humans are incredibly plastic meaning that the environment component of their phenotypes can adjust through life Adaptation : genetically based traits that increase an individual's ability to survive and reproduce in a given environment Homeostasis:steady state,healthy range of environment for an individual 4 levels of Adaptability 1. genetic adaptation *at population level* -inherited and irreversible -are selected for over many generation 2.developmental plasticity -changes during growth and development -at the individual level -irreversible 3. Physoiological Adapatability -acclimatation -at any time in an individual's life (@ individuals level) -reversible -ex:tanning, attitude -can arise in seconds,minutes days 4.cultural/behavioral adaptability -use of material culture to make living in an environment possible Stages of Growth Life history: timing and details of growth events and developmental events from conception through death1.prenatal 2.postnatal 3.adulthood Modern Variation Climate -humans are warm blooded -body temp is : independent of outside temp and constant Genetic adaptations body proportions -volume of your body affects how much heat we generate -surface area of your body affects how much heat can escape through your skin -same volume but sinner arrangements= greater surface area Bergmann's Rule -volume arranged in short, stout body has less surface area **small surface area= conserve heat=adapted to colder climates** -volume arranged for small/skinny body=more SA **more surface area= more heat release=adapted to hot climates Allen's Rule Another way to increase surface area is to arrange the same volume so the limbs are skinner -cold adapted body=short, thick limb -heat adapted body= long thin limbs Physiological adaptability- to climate: short term sweating=evaporation of water removes body heat=cooling shivering=skeletal muscles shake=create heat -too hot of an environment- vasodilation **blood vessels expand (bring blood toward skin,releasing heat) -too cold-vasoconstriction **blood vessels contract (move blood to core) Modern Human Variation: High altitude -all contents except for australia and antarctica have high altitude regions *stressor :something that moves you out of your normal homeostatic range **stressors in places with high altitude= less oxygen less vegetation,more uv radiation, more challenging terrain -No universal way to adapt to high altitudes -High ultralight Radiation *thinner atmosphere filters less UV radiation **every 1000m increase in altitude=10-12% increase in UV levels **consequences (of high UV rays) -skin aging=collagen fibers in skin break down -DNA mutations -tanning: biological response to UV exposure **melanocytes in skin make the pigment melanin-low oxygen concentration 10,000 ft or more above sea level Lower air pressure (air expands) ** take in fewer oxygen molecules with each breath -Genetic adaptation to high altitude Tibetan shave 15+ gene mutations for oxygen use compared to the chinese **split from hans chinese-3000 years ago **mutations-affects hemoglobin concentration and red blood cells count (allowing those in high altitude to get more oxygen to cells -found in <10% of Han chinese (but found in many of Tibetans) -in 90 % of tibetans -high altitude developmental plasticity ** in response to less oxygen -greater lung volume -larger heart(more muscle,contracts more powerfully) ** in response to nutritional deficiency -slowed growth and development (delayed puberty) - shorter stature **these changes are irreversible -Physiological adaptability to high altitude **in response to less oxygen -increased respiratory rate, heart rate, and rbc production **in response to higher UV radiation -tanning **reversible once you leave high altitudes** Modern human Variation: Nutrition -stressor:dietary inadequacy -most of the world's pop is undernourished (<2000 calories per day) -results in : stunted growth -suppressed immune system -shortened life expectancy -insufficient balance of macronutrients (carbs, fats, proteins) and micronutrients (vitamins and minerals) ex: kwashiorkor- bloated stomach in children caused by lack of protein(even when child consumes enough calories) -genetic adaptation to mutation *lactose:complex sugar found in milk -digest it with the protein lactose -most mammals stop producing lactose after they are weaned off of breast milk Lactose intolerant : cannot digest milk (most common condition) -lactase persistence allele: continued production of lactose **homozygous dominant- produce lactose **heterozygous-limited lactose **most common in populations that domesticated dairy animals (ex.northern europe) The History of RaceJR blumenthal proposed 5 races of humans **degenerative hypothesis** Franz boas did cranial measurements on immigrants and was responsible for disproving race as a biological reality. Intrapopulation Variation > interpopulation variation -most variation occurs within rather than bw so called “races” Richard Lewontin -looked at blood groups,serum proteins, red blood cell enzyme variants **between populations=50% of variation **within the same population=85% of variation 2.different traits =different groups (average height) Even if you try to make groups based on biology not every human fits into these groups 3.human variation is not discrete Its clinal Cline:gradual change in phenotype over geographic distance Melanin: a pigment in the outer layers of the skin Skin color is produced by combinations of different pigments More melanin production=darker skin Melanin absorbs UV radiation from the sun,preventing it from penetrating the skin Tanning:Uv radiation stimulates melanin production Lighter skins=more UV light penetrates Dark skin= less UV light penetrates Darkest skin=in areas of high UV exposure (ecuador) Natural Selection: folate synthesis Folate: a vitamin essential for synthesis and repair of DNA Without enough folate: fetal development can be harmed So why isn't light skin selected against? Need UV radiation to make vitamin D Not enough vitamin D- rockets and osteomyology Environments with less UV radiation alleles for less melanin (lighter skin) favored Assessment of Geographic Ancestry ancestry= part of the world from which you and your family originate Past: visual examination of the skull now=measurements of the skull **geography and climate influence cranial dimensions Race is a social reality Low birth weight a race?