Anthropology Notes PDF

​ Blending theory of inheritance ​ Gregor Mendel (1822 - 1884) ​ Breeding experiments on strains of peas which were pure for 7 different discreet combinations ​ 28,000 plants; 400,000 seeds ROUND + WRINKLED (pure) = All ROUND (self-...

​ Blending theory of inheritance ​ Gregor Mendel (1822 - 1884) ​ Breeding experiments on strains of peas which were pure for 7 different discreet combinations ​ 28,000 plants; 400,000 seeds ROUND + WRINKLED (pure) = All ROUND (self- fertalized) 3/4 ROUND, ¼ WRINKLED ​ NO blending ​ There are physical units of inheritance that maintain their identity when passed form parents to offspring (genes) ​ Dominant, recessive ( codominance) ​ Locus: physical location of genes ​ Alleles: different forms of the same gene ​ Homozygote( pair of same allele) , heterozygote ( pair of different alleles) ​ Genotype ( specific combination of allele), phenotype ( gene= morphological result of alle combination) ​ Monogenic trait= determined by one gene; such traits are discrete ​ Polygenic trait= inflcluenced by multiple genes; such traits are continuous ​ polymorphism = existence of 2 or more alles at a locus and thus 2 or more genotypes at that locus ​ Chromosomes ○​ Containers of DNa ○​ 23 pairs of chromosomes( 1 from each parent) in each human cell= 46 total  ○​ Meiosis= cell division in gemr cells producsinh gamhetes( egg cell, sperm); sperm + egg cell -> zygote ○​ mitosis= cell dicision in all other cells ​ DNA ○​ Humans= 21,000 genes ​ Produces at least 100,000 proteins= a primary function of genes. ​ = 2-3% of all DNA directly and consistently involved in protein production ​ DNA without a clear purpose used to be called junk DNA but is now understood as the location of regulatory genes ○​ Only 25% of dna is considered junk dna ​ Noncoding RNA ​ Epignetics ○​ Changes in Dna structure that dont involve changes in base sequence ○​ Methylation ○​ Response to stressfull environment ○​ Can affect expression ofn at least some genes; e.g. regulatory ○​ At least some are transmitted to offspring ​ Exons (coding), introns (non-coding) ​ Second category: regulatory genes ​ Multiple operating but in different possible combinations ​ enhancers , silencers ​ Homeobox= Hox genes ○​ Codon= 3 consecutive bases= smallest genetic unit of functional information ​ Each codon codes for a specific amino acid = units which make up protiens; I.e codon sequencwe deterimines amino acid sequence -> protien structure-> protien function ​ One gene- one protein model ○​ Located in chromosomes in nucleus of all cells ○​ Double helix; backbone =phosphate + sugar= deoxorhybose ○​ rungs= pairs of bases ​ Adenine + thymine ​ Cytosine + Guanine ​ Evolution= change in the frequency of alles in a breeding population from generation to generation ○​ Forces of evolution ​ Mutation  ​ Ulitimate source of all new genetic variation = change in the seuqence of DNA bases ​ Meiosis ​ spontaneous mutation rate; mutagens ​ Occurrence of mutations is random ​ Mutations rare ​ Once believed that almost all mutations in current species were deleterious= decreased probability of survival ​ gel electrophoresis: detects differences between individuals in the amino acid dequence of the same protein; indirect assessment of genotype ​ About 25-30% of all protein-producing loci are polymorphic in a wide variety of species ​ Explanation: natural selection is not operating; i.e, one for, of the protein is not more efficient than another ​ Neutral mutation: changes in codon sequence which are neither advantageous nor deleterious ​ Now appears that neutral mutations are not as prevalent as once thought ​ Drosophila ○​ Appears 20% of junk actually being acted uponby natural selectionction at very low intensity ○​ Only 5% appears to be neutral ​ Evelitionary importance of neutral mutations* ○​ Increases the importance of drift ○​ May provide an advantage in the future ​ 13 rabbits introduced into australia in 1859; 600 million by 1940 ○​ Myxamatosis virus introduced to curtail population. ○​ Virgin population not exposed to virus ○​ Rabbits possessing neutral mutations more likely to survive; virus also became less virulent ​ Gene flow ​ Movement of individuals from one breeding population to another ​ Mate exchange ​ Effects on genetic variation ○​ Increased genetic diversity within breeding population ○​ Decreased genetic difference between breeding populations ​ Natural selection ​ Must be a stress resulting in differential mortality; often this involves relatively small differences between groups of individuals in probability of survival ​ Individuals who are best able to cope with the stresses of their enviroment ​ Types ○​ Directional ​ Polygenic trait: ​ Peter and Rosemary Grant: medium ground finch in galapagos ○​ Much larger Variability in beak size compared to other finches ​ 1976: birds tagged and weighed; 5 inches of rain (normal) ​ 1977: 1 inch of rain: no breeding and 85% of medium ground finches died ​ 1978: back to 5 inches of rain ○​ Suvival not random; larger birds more likely( no guarantees) to survive ​ Plants prodicing large seeds tend to live in low-lying areas where there is greater access to ground water and more likely to survive then plants producing small seeds which tend to live in high lying areas ​ Increase in seed size = increase in seed toughness ○​ Process: ​ Larger birds have larger and stronger beaks ​ Superior biological design for this specific environment ​ Better adapted ​ Larger average body size next generation  ○​ What happemded with return to normal levels of rainfall ​ Gradual decrease in average body size until 1983 ○​ El nino: 8 months of rain -> flooding ○​ Small seeds are consumed more effectively by sma,l birds which increases chance of survival and decreases body size ○​ Enviromemts sometimes remain fairely constant on average over long periods of time but there can still be considerable environmental fluctuation over a short period of time which can result insubstantialgenetic chnage ​ Monogenic trait (discrete phenotype): ​ Peppered moth; 1848: color dterminee by 1 locus= monogenic; 1% black, 99% mottled gray; loght colored lichen on tree trunks ​ Industrial revolution: dark moths had a 15% greater chance of survival ​ 1898：> 98% were black ​ Clean air act pattern reversed ○​ Stabalizing selection ​ Monogenic traits: (discrete phenotype)= balanced polymorphism ​ Heterzygote is better adapted than both homozygotes ​ As a result, both alleles are maintained in the populations at some stable rate, depending on magnitude of difference eon probability of survival ​ Polygenic trait: (continous phenotype) individuals with average phenotypic traits have increased probability of survival ​ Sickle cell anemia ○​ About.27% of americans of african ancestry have SCA = 100,000 individuals at any one time ○​ About 8.3% are herterozygotes ○​ Frequency of S allele is 20 - 30 times greater in some parts of western and central african populations than in the US ○​ High frequency of S allele is proportional to highfrequnecy of S allele ○​ Conclusion: bothAA and AS are both better adapted than SS individuals in every environment but AS are better adapted in an environment with endemic falciparium malaria= balanced polymorphism ○​ Hunter and gatherers propr to 1500-2000 before present: small populations, mobile -> minimal if any malaria until ​ Bantu horticulterists: -sedentary - large population size. -Cassava and yam farming -using iron tools - Slash and burn -abandoned field -thatched roofs ○​ Genotype involved in producing Hb: ​ AA= normal produced ​ AS= sickle cell trait (carriers, less likely to hospitilized) ​ SS- sickle cell anemia ​ ○​ Plasmodium falciparium ○​ Life cycle involves humans and anopheles mosquitos ○​ Etiology of SCA: ​ Mosquito bites human in correct phase of parasite life cycle ->  ​ Blood stream -> ​ Liver -> ​ Blood -> ​ Red blood cells where uncontrolled reproduction takes place ​ Bursts RBC ​ Transfered back to mosquitos ○​ Found primarily in people of west african descent ​ Effects of low oxygen pressure on hb/rbc: decreased ability to load oxygen at the lungs and decreased amount of oxygen which is released to tissues. Descrsed lifenspan. Decreased* ​ Change in1 out of 438 bases-> change in 1 out of 146 amino acids in beta chain of hemoglobin ​ Codominance ​ Suppose there are two alleles ( A and s) at a locus ○​ Disruptive ​ Monogenic trait: both homozygotes are fitter than the heterozygotes ​ Polygenic trait: Extremes fitter than the middle value ​ enviroment as a result of their supeoror biological design ○​ Higher chance of survival ○​ Higher chance of reproducing then the less well adapted ○​ Greater representation in the next generation. ○​ Fitness ​ Number of offspring that survive to reproductive age ​ Fitness vs adaptedness  ​ ​ Drift ​ Influenced by: lower population size -> greater dirft and vice versa. Greater frequency of neutral mutation -> greater drift ​ Intergenerational drift= offspring gene pool differs from parental gene flow as a result of sampling error in the formation of zygotes ​ Effective population size = individuals actually involved in producing the next generation; about 40% of hunting and gathering bands. ​ Greater varation in reproduction -> greater effect of intergenerational drift ​ Founders effect: ​ Fissioning ​ If the founding population is not representative of the original population -> founders effect possible if restricted gene flow ​ Amish and ellis van creveld syndrome ○​ Gene carried by samuel king or his wife, who migrated to PA in 1774 ​ Pingelap Atoll ○​ Typhon in 1775 killed all but 30 indivudals ○​ Initial population of about 1000 ○​ One survior was a color blind chief ○​ Chiefs have more wives -> more offspring ○​ 5% of the population are now color blind ​ If drift is the only force operating -> fixation ​ Affects of drift: ○​ Greater genetic differences between breeding populations ○​ Less genetic variation with breeding population ​ Evolution has occurred in the last 10,000 years ​ Lactose digestion ​ Inuit and cold ​ Sickle cell and malaria ​ High altitude ​ Skin color and ultraviolet radiation ​ Variation in average body size ​ Genetic resistance to HIV ​ bottleneck effect: ​ Population size reduced by a disaster ○​ Macroevolution: evolution over a long period of time we cant observe. AKA, large scale genetic changes, including extinction and speciation, over relatively long periods of time ​ Primary goal: reconstruction of phylogenies ​ Fossil record  ​ Biological similarities and differences of living species ​ Assumption: species which are biologically simikar because they have a recent common ancestor ​ Parallel evolution: two species have s distant common ancestor by they continue to evolve in a similar manner because they are exposed to similar environmental stress -> natural selection produces similar solutions ​ Convergent evolution: two spedies have a very distant common ancestor byt eventually occupy similar environments -> become more alike over time due to natural selection producing similar solutions ​ Ernst mayr (1942): biological species= group of organisms which can produce fertile and viable offspring ( reproductively isolated) ​ Female horse + male donkey = mule (sterile) but hybrid vigor ​ Leopard frog ○​ Coast of U.S from new england to texas ○​ Any two adjacent groups are phenotypically similar but the phenotypic differences increases with distance ○​ Greater the difference the greater the mortality; no survivors in matings between two geographic extremes ​ Hybridization ○​ 25% of plant species and 10% of animal species have been affected by hybridization ○​ Olive and hamydras baboons, ethiopia ○​ Reproductive isolation is generally adequate definition but there are exceptions ​ Population genetics ​ Synthetic theory of evolution ​ Hardy-Weinberg Theorem ○​ Microevolution: evolution over a long period of time we can not observe ​ Constrained by the available biological variation, which is a function of the past evolutionary history of a species ​ Macroevolution is also constrained by other factors, particullay ecological factors ○​ Ecology ​ Study of ecosystem = system with which soecies exists, includes physcial enviroment and other species occupying the same region ​ Ecological niche ​ Food (trophic) pyramid ​ producers(plants) -> herbivores (termite)-> secondary consumers (coyote)-> tertiary consumer (lion) ​ Principle of competitive exclusion= only one species can occupy given niche at any one point of time ○​ Primary macroevolutionary outcomes: ​ 1. Extinction ​ 2. What we generally simply refer to as speciation ​ 3. Phyletic evolution: small varability in change in a population over a long period of time, small eniugh to be considered normal variability ○​ Species are made up of breeding populations, each of which is undergoing somewhat different patterns of mutation, gene flow, non-random mating, natural selection, and drift ○​ Branching evolution ​ Reproductive isolation ​ Geographic isolation ​ Behavioral isolation ​ Isolated groups dont go extinct ​ Barriers to gene flow are not removed ​ Isolated breeding populations undergo suffucentky different patterns of evolutionary change(drift, natural selection) that, even if the barriers are removed, they can no longer produce fertile and viable offspring with parental populations ○​ punctuated equilibrium ​ Is speculation simply micro-evolution over very long periods of time? ​ Theory of punctuated equilibria (PE): many lineages exhibit little change in the palenotological record for long periods of time and then undergo short periods of rapid change, generally in association with both extinction and speciation ​ Species-level selection ​ Can pattern in phenotypic change associated with PE be caused by small but consistent evolutionary change? ​ Regulatory genes? ○​ Sociobiology ​ Study of the genetic basis of this behavior, as acquired by the operation of natural selection ​ Genetic determination vs. genetic basis ​ Genes playing a role doesnt mean that the role is a large one or that only one gene is involved ​ Altruism: self-sacrifising behavior ​ W.D. Hamiliton: kin selection ​ Assume unit of selection is a group of related individuals who share genes by ancestry ​ Inclusive fitness: ○​ Total genetic contribution, both through own offspring and offspring of related members of your social group, who survive and reproduce ​ Altruism directed towards non-relatives? ​ Reciprocal altruism  ​ More social female baboons has greater infant survival; but why? ​ E.O. Wilson ​ Failure to consider alternative hypothesis: behavior transmitted culutarally ​ Sarah Hrdy: Langur monkeys ○​ Ge(4pi^2/GM)rne pool ○​ Suppose population= 50 AA and 50 BO at ABO locus ​ Total alles= ? 200 ​ A alles = 50 * 2 = 100/ 200 = 0.5 alle frequency ​ B alles = 50 * 1= 50/200=0.25 alle frequency ​ O alele = 50 * 1= 50/200=0.25 alle frequency ○​ Breeding population ​ Primary unit of evolution