Why would people range from tasting bitter things very strongly to very weakly. Bitterness often signifies something poisonous, so it may be useful to know For the moderately tasting people it still has some bitterness. Not being able to taste it allows people to possibly eat foods other people cannot bear to eat. What does grapefruit taste like to you? What is the genetic code? What does the genetic code do? What is the structure of human variation? Three levels of magnificationare useful way to think about genetics and evolution biochemical - what are genes, what do they do, how do they change? chromosomal populational At the biochemical level the central dogma is the concept that genetic information flows from DNA to RNA this orients us towrad the basics of genetics and how we use the science to understand human evolution what is a protein? protein synthesis is the other vital function of DNA begins with transcription, the synthesis of another type of nucleic acid, RNA, specifically mRNA this occurs in the nucleus The mRna leaves the nucleus for the ribosome in the cytoplasm translation occurs in the cytoplasm when the mRNA attaches to the ribosome and is translated into amino acids Alternate - variant - formas of a gene are called alleles alleles are coded for by different sequences of nucleotide bases in the same region of a chromosome a single base subsititution leading to a single amino acid substitution in the hemoglobin beta chain is the cause of sickle cell disease. A mutation is an alteration in the sequence of bases during DNA replication -insertion of new base or bases -deletion of existing base or bases -rotation of a base pair Changes in the number and order of nucleotide bases and genes makes each of us unique. Allele counting method is easily applied to loci with codominant alleles Used for measuring gene pool p = frequency allele A = (72+48)/200 = .06 p+q = 1 Breeding or Mendellian population Genes come from proteins Gene codes for a trait, alleles are a form of that www.genome.gov Duffy O gene codes for a protein on the red blood cells that doesn't allow Malaria to infiltrate red blood cells Natural selection is the differential survival or reproduction of genotypes -need a method to determine the characteristics of gene pool Baseline Situation: no evolution G.H. Hardy Blue eyes question Mathematical model of conditions under which no evolutionary change Hardy-Weinberg Equilibrium describes the conditions under which gene and genotype frequencies remain the same -one genetic locus -two alleles p = allele frequency of allele A q = allele frequency of allele a -predict genotype frequencies -frequency of genotype AA = p x p -frequency of genotype Aa = 2pq -frequency of genotype aa = q x q Conditions: absence of forces of evolution the population has to be large enough so that random genetic drift is not operating there is no inflow or outflow of genetic variation mating is random (with respect to genotype) natural selection is not occurring A single nucleotide base change in an intron in a gene adjacent to the gene producing eye pigment accounts for blue: nonblue eyes Number of people: 100 Number with blue eyes: 25 Genotype freuqency: .25 Blue eye allele frequency q = .5 Nonblue eye allele frequency p = .5 intron - get transcribed into rna but don't make final protein Natural selection is another force of evolution the differential survival of genotypes in an environment brings about variation within a species and brings about new species the result is that... Falciparum malaria and the balanced polymorphism for HbA/HbS is the classic example of natural selection in humans Malaria kills > 1 million children every year 1~5% of humanity suffers >2 billion people are threatened with malaria because they live in a malarious area enormous public health issue COnsider malaria from the standpoint of evolution by natural selection: is everyone exposed equally likely to get sick? no is everyone exposed equally likely to die? no malaria has acted and continues to act as an agent of natural selection in human populations human activities are largely responsible for creating the conditions that allow malaria to flourish slash and burn increase the population of mosquitos malaria infection involves three organisms host - humans infectious agent - plasmodium -protozoan parasite -four speicies of malaria infect us: falciparum, vivax, malariae, ovale vector - female anopheles There is a geographic overlap of two deadly blood diseases in sub-Saharan Africa -malaria mortality in sub-Saharan Africa -sickle cell anemia mortality in sub-Sahara -three important interacting factors -physical environment -subsistence mode - slash and burn agriculture -human biology Genotypes have differential survival and this results in natural selection by falciparum malaria HbAA genotype -high mortality rate due to falciparum malaria -no mortality due to sickle cell anemia HbAS genotype (codominant alleles) -low mortality rate due to falciparum malaria -no mortality due to sickle cell anemia HbSS -low mortality rate due to falciparum malaria -high mortality due to sickle cell anemia Mechanisms whereby HbSS homozygotes have higher survival rates -rbs circulate carrying oxygen -HbS containing rbc's marginate and sickle -deformed rbc's don't deform to pass through capillaries, burst and release plasmodia -deformed rbc's are removed by spleen along with plasmodia Darwinian fitness of genotypes maintains a balanced polymorphism what maintains this is physical environment, human biological variation, culture responses to this situation include prevent or reverse sickling, bed nets, quinine Directional selection is another type of natural selection working in human populations The lactase persistence polymorphism accounts for variation in ability of adults to digest the lactose in milk One locus (LCT), two alleles P is dominant (P for persistence) and these individuals (PP and PR) continue to produce lactase throughout their lives R is recessive and the RR individuals stop producing lactase around 4 years of age The frequency of lactase persistence varies globally Northern European pops have high freq. e.g.>90% Southern Europeans and Middle Easterners have less ~50% in Spaniards Asian African and New World pops have very low freq. ~1% in Chinese Exception: Lactase persistence is common in pastoral pops from East Africa Among Europeans, a single mutation in a promoter gene for lactase accounts for the continued synthesis of lactase and obtaining all the benefits of milk Among African pastoralists, a different mutation in the promoter gene for lactase accounts for the same phenotype Convergent evolution refers to two or more populations independently evolving the same trait Two different pops were under similar dietary pressures involving milk They converged on the same solution of prolonging the production of lactase How long did this take? ~6-8,000 years in Europe ~3-7,000 years in East Africa Does drinking milk in liquid form have benefits that other dairy products do not proivde? The sugar lactose provides calories The milk protein loctoferrin is an important antibacterial protein Milk provides a clean source of water Milk enhances the absorption of other nutrients in milk such as calcium The tect box "Got Milk?" on pp 90-91 has some misleading statements "Most common protein deficiency..." "Feel discomfort..." "...primitive (unevolved) condition..." "...a condition that affects billions of people today." Stabilizing selection is another form of natural selection - natural selection actively maintains the same allele frequencies Birthweight is a classic example, small and large babies have higher mortality rates Hardy-Weinberg Equilibrium conditions, continued Mating is random with respect to genotype Potential violations Potential genetic consequences of violations beneficial costly Cultural preferences for marrying relatives are the most common violation The result is more homozygotes that predicted by the Hardy-Weinberg equilibrium Consaguineous marriages are common globablly Population is large Random genetic drift if population is small random fluctuations random changes in allele frequencies Potential genetic consequences Beneficial Costly 4-10% of the population of Pingelap Atoll has a recessive form of colorblindness A typhoon in 1755 killed many people and just 20 survived. All the people with achromotopsia trace their ancestry back to one man, a chief who survived the typhoon and had have been heterozygoues for this trait This would be unlikely in a large population or one that was open to immigration About 30% of the alleles at this locus are for achromostopsia No migration is occurring - gene flow Introduce new alleles... Migration, the movement of people into or out of a population, can change allele frequencies Saipan Island ABO blood group freq before and after WWII is an example Zuni Indian cystic fibrosis allele Forces of evolution mutation crucual role rate varies from many loci means Cultural factors may change the gene pool Hopi Albinism - the agricultural practice of colored men going to the fields to work while the albinos stayed in the willages Forces of evolution gene flow random genetic drift cultural factors natural selection - the only one that garantees favorable genes over times Is race a valie, biologically meaningful concept? Pan troglodytes is the scientific name for the chimpanzee. There are three subspecies. Sub species designations are optional and are used sometimes to reflect biological variation within a species that is geographically distributed Homo sapiens is the scientific name for humans. Are there sub speicies? Outcome of evolution and... Polytypic species - many forms Race is an arbitrary sub-classification within a species (in contrast with species) Not a required taxonomic designation Vs. human race popular usage A common definition of race: group of local populations that can be differentiated from others on the basis of one or phenotypec traits Another common definition is a genetically distinct group What do growth and development tell us about human variation? How do people adapt to environmental extremes and other circumstances? Tibetans have a major gene (a) for high oxygen saturation of hemoglobin %oxygen saturation refers to the proportion of hemoglobin molecules carrying oxygen The autosomal dominant allele (a) results in 10% higher saturation Natural selection requires heritable variation There is evidence of natural selection ongoing in Tibet today Differential reproduction and survival of genotypes Tibetans have genotypes... Concept check on adaptation to high altitude hypoxia First exposure - some people have symptoms of Acute Mountain Sickness Functional adaptation is improved blood flow in Tibet, higher hemoglobin concentration in Andes Genetic... Potential for synthesizing vitamin D varies relative to UV radiation Exposure to UVR influences the burden of disease including skin cancer Small amounts of UV are beneficial for people and essential in the production of vitamin D Inadequate vitamin D increases the risk of many illnesses UV radiation... Insufficient sunlight can result in vitamin D deficency Rickets in children - legs are bowed outward and pelvis bone is mishapen osteopenia, osteoporosis, and fractures in adults Increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases You need to have vitamin D to absorb calcium UV radiation exerts a biological effect on our bodies depending on how much of it is absorbed or reflected Melanocytes produce melanin that largely determines skin color. The amount of UV radiation that penetrates our skin to reach the melanocytes depends largely on skin color UV A penetrates further than UV B UV radiation, Vitamin D synthesis and skin pigmentation are related V D synthesis occurs in skin UV light transmission to synthesis site and to DNA in nucleus depends on amount of UV radiation transmitted lightly melanized skin reflects more, transmits more heavily melanized skin absorbs more, transmits less melanin contact influences vD synthesis V D has many benefits Prolonged human exposure to UV radiation may result in Acute and chronic health effects on the skin, eye, and immune system Suntanning is one consequence Sunburn, cell death and peeling is one consequence Photoaging is one consequence UV radiation has costs for human health Causes DNA damage Increases the risk of skin cancer Increases the risk of photodegradation of nutrients circulating in the blood stream including folates and v D itself Recent U.S. skin cancer statistics illustrate a large burden just in our own country One million new cases of basal or squamous cell carcinoma in 2009 1996 ~38,000 new cases of malignant melanoma... Skin color varies with latitude and annual UV radiation Skin melanin influences the amount of V D synthesized Natural selection is acting along the global gradient of uv radiation Favors highly pigmented skin at low latitudes Skin cancer Photolysis of important nutrients Immune suppression Favors lightly pigmented skin at high latitudes vitamin D synthesis rickets Light pigmentation is found at high latitude in Europe and Asia The genetic variants responsible differ SLC24A5 is a locus that influences skin color 93% Africans and East Asians have one allele 98% of Europeans a different allele The gene regulates metabolism in the melanosome SKin color is polygenic, quantitative trait Another genetic locus, the melanocortin gene (MC1R) also contributes to skin color variation Homozygotes for one variant usually have very light skin and red hair because they produce very little melanin This gene is found in many species including us, the Neanderthals, wooly mammoths, dogs and foxes Concept check on adaptation to uv radiation first exposure: pssible sunburn, DNA damage, increase melanin production functional adaptation: tanning skin thickens genetic adaptation: high melanin production in high uv environments, convergent evolution for low melanin production... Chapter 6 asks four big questions What is a primate? What are the kinds of primates? How do primates acquire food? This chapter provides a transition from study of evolutionary principles and living people to the study of fossils Priniciples of evolution form the framework for interpreting a variety of evidence DNA, living people, living primates, fossil primates and people and DNA The Primate Order is a taxonomic group first identified by Linnaeus Order - taxonomic group carnivora - cats, dogs, weasels chiroptera - bats insectivora - moles and hedgehogs The primate order has more than 250 species Species - Homo sapiens Genus - Homo Family - Hominidae Superfamily - Hominoidea ... The phylogeny of the Primate Order describes the evolutionary relationships among the primate species Phylogenies are based on patterns of shared adaptive physical features to help determine the degree of relatedness among species Primates have opposable thumbs (ability to climb and grasp things), two forward facing eyes (gives us depth perception) Prosimions, homonoids... Phylogeny is an evolutionary tree with groupings of animals or plants with similar features that shows their relatedness and divergence An ancestral trait is one that appears earlier in the evolution of a make lineage or branch that the group of species of species of interest A derived traits is one that appears later in the evolution of a lineage or branch Groupings of derived similarities are used to construct phylogenies Shared derived characteristics of primates relative to other orders are ancestral to existing primates climb by grasping forward facing eyes Primates have many shared, derived characteristics (e.g. fingernails) many primate features anable life in the trees and are called arboreal adaptations primates eat a wide variety of foods primates make large parental investments, they put a lot of time and energy into their offspring Shared derived characteristics of leaf-eating monkeys identify them as a group within the Primate Order Colobines are leaf-eating and have a foregut with enzymes and bacteria for fermentation - analagous to cows Baboons eat more grass and seeds and do not have the fermentative foregut The study of non-human primates helps us determine the evolutionary history of our own ancestral and derived traits What are the human derived traits? When and ender what environmental circumstances did they evolve? What are our ancestral traits? How did they enable or constrain evolution of our derived traits? We interpret the patters of similarities and differences between human and nonhuman primates reason by homology - similar traits we share with a wide range of other species due to common ancestry (not unique because inherited) reason by analogy - similar traits we share with species in similar environments What traits here are shared, derived traits and what are derived? Primate conservation is an urgent priority. Hunting for bushmeat and habitat destruction are problems Chapter 7 asks three big questions What are fossils? What do fossils tell us about the past? What methods do we use to study fossils? Fossils are the inorganic remains of once living organisms Occasionally dead organisms do not decompose completely, but instead are mineralized, preserved and fossilized Fossils are rare Fossilization process is rare Recovery and interpretation is rare What do we want to learn about a fossil? Phsyical characteristics, morphology e.g. how big, how many limbs, posture What is it? e.g. belong to an existing species? Genus? What was its environment like? How did it behave? When did it live? Taphonomy is the study of what happens from the time of death of an organism to the time of recovery by scientists Information about what materials are likely to fossilize Information about what environments are likely to fossilize Information about distribution of materials after death death, with time bones remain (skin decomposes, bones are broken by trampling, bones are covered by sediment or water Two general types of dating techniques tell us how old the fossil is Relative dating techniques tell us which is younger, older, or the same age Stratigraphy - the "principle of superposition" states that what is lower down is older, the shortcomings include: don't know how much older and can't compare different sites easily Faunal succession - "animal change" Chonometric (Absolute) dating techniques tell us the number of years ago provides estimates of the specific time of existence in years before the present ability to know how old and to compare sites most techniques are based on the principle of radioactive decay of natually occurring isotopes... radiometric dating relies on regularly occurring, natural processes and the concept of half-life rely on the natural, clocklike decay of unstable isotopes of an element to more stable forms. Carbon-14 Dating Logic Living org. have known ratio of c-12 and c-14 Radioactive decay occurs at constant rate - measured as half life Measure ratio of c-14/c-12 in the fossil Infer how long c-14 has been decaying This requires organic remains It is most informative for the past 50,000-75,000 years (less precise up to 95,000 years ago) Because the amount of c14 becomes too small to measure Potassium-argon dating is based on the principle that unstable isotopes of potassium in volcanic rock decay into stable argon No argon gas was present at formation of rock All argon now in the rock has accumulated since formation Known half-life of Potassium40 decay into Argon40 is 1.3 billion years; measure the ratio of Ar40/40K40 Useful for materials older that 200,000 years Requires volcanic matter Doesn't date the fossil directly Pratically, it is useful for samples older than 500,000 years, some push it to more recently at 200,000 only .001% of the K40 in a rock would have decayed to Ar40 at 200,000 years detection limits of equipment are reached Paleomagnetism is a calibrated relative dating technique that combine approaches Sometimes the north and the south poles swap places.What Chapter 8 - why become a primate? who were the first primates? who were the first higher primates? what evolutionary developments link past and living primate species? What accounts for the origin of Primates? Evolutionary theory predicts changing biological characteristics and adaptations Many new ecological niches evolved in the period just before the earliest primates appear in the fossil record Dinosaurs had gone extinct, flowering plants and insects evolved and many new niches opened Primate phylogeny describes the evolutionary relationships among primate species The Primate family tree is the result of millions of years of primate evolution The record of primate evolution starts in the paleocene, 65mya Earth history is divided into eons, eras, periods, and epochs, all of which are assigned numerical ages. (ceno-means recent) Molecular data indicate that the colsest relatices to the Primates are the Dermopterans Colugos or flying lemurs are not lemurs and they do not fly, instead they have a specialized skin fold called a patagium, that strectches from the neck... The paleocene Plesiadapiformes are questionable primates and often called proprimates Paleocene was 65-55mya The taxonomy of the Plesiadaptiformes has been debated because they have only hints of primate features Debate... Carpolestes simpsoni may link the proprimates of the paleocenne with the eurpimates of the eocene Early graspin is an important feature, grasping hands, fingernails, but doesn't have forward facing eyes and depth perception Quiz 3 occurs in class on Wednesday The materials covered include classes... textbook chapters 5-8 plus the online materials An approach to studying is to start with the Big Questions posed at the beginning of each chapter Is race valid, biologically meaningful concept? What evolutionary developments link past primate species and living ones? Notice that the big questions are answered briefly at the end of each chapter. Pay attention to the concept to help keep track of the big picture Class materials update/correct the text, elaborate on the big questions and the concepts and the examples. An archbishop and four bushmen walk into a lab These five men from South Africa provided their DNA for scientific analysis There is more genetic variation between two of the bushmen than between the average Eauropean and East European How does this study fit into our class topic? This shows that race is less biological than cultural. This genetic variation will be advantagous for adapatation in the future Chapter 9 asks four big questions What is a hominid? Why did hominids evolve from an apelike primate? Who were the first hominids? What was the evolutionary fate of the first hominids? The text consides the Pre-Australopithecines and the Australopithecines Sahelanthropus and Ardipithecus These lived... Prof Owen Lovejoy proposed a sexual selection model for the origin of bipedalism Novel reproductive strategy provisioning of female and infant by male infant care and feeding by female pair bond between adults Outcome was shorter interval between births More offspring born, more offspring surviving, more need for provisioning Avoided demographic decline of great apes We have reproductive capacity and flexibility that the apes do not This hypothesis considers the combination of bipedality and small canines Three new behaviors were associated with homonids ability to exploit both trees and ground Regular food carrying Pair bonding Reproductive crypsis in which females do not advertise ovulation There are many hypotheses about the origin of bipedalism Carrying (tools, food, infants)... Australopithecus anamesis was found in Kenya and Ethiopia, dated to 3.9-4.2 mya Evidence of bipedality Tibia is like upright bipeds Foramen magnum Other evidence of hominid status Good transitional form between Ardipithecus and A. afarensis Molar form and thick enamel Canines smaller, lower premolar somewhat... East and Central AFrica 1000 individuals found Environment Hadar, Ethiopia Laetoli, Tanzania Different from pre-A Is a hominid because it is bipedal Mosaic evolution Sexual dimorphic body size Stasis for about one million years Quiz Four Covers the readings and classes since the last quiz... Big Questions, Concept Checks