5 Evolution and Genetics Anthropology Appreciating Human Diversity

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5 Evolution and Genetics Anthropology: Appreciating Human Diversity 14 th Edition Conrad Phillip Kottak

5 Evolution and Genetics Anthropology: Appreciating Human Diversity 14 th Edition Conrad Phillip Kottak

2 Evolution and Genetics • • Evolution Genetics Biochemical, or Molecular, Genetics Population Genetics

2 Evolution and Genetics • • Evolution Genetics Biochemical, or Molecular, Genetics Population Genetics and Mechanisms of Genetic Evolution • The Modern Synthesis © 2011 The Mc. Graw-Hill Companies, Inc.

3 Evolution and Genetics • What is evolution, and how does it occur? •

3 Evolution and Genetics • What is evolution, and how does it occur? • How does heredity work, and how is it studied? • What forces contribute to genetic evolution? © 2011 The Mc. Graw-Hill Companies, Inc.

4 • Why tall parents have tall kids? • Does obesity run in the

4 • Why tall parents have tall kids? • Does obesity run in the family? • How much do genes influence in our bodies? – Human biology is plastic but only to a certain degree (blood type) – Cultural (medical) solutions exist for genetic disorders © 2011 The Mc. Graw-Hill Companies, Inc.

5 • Is culture intervening too much with intrinsic biological features? – Hearing impaired

5 • Is culture intervening too much with intrinsic biological features? – Hearing impaired community’s fear that hearing aid implants are a threat to the deaf subculture. – Plastic surgery and genetic screening might create a future in which physical perfection might reduce human diversity and increase socioeconomic inequality. © 2011 The Mc. Graw-Hill Companies, Inc.

6 • How about the long-term plasticity of human genome? – Evolution: All living

6 • How about the long-term plasticity of human genome? – Evolution: All living organisms come from ancestors that were different in some way. – Evolution is a fact. – The scientific theory of evolution is the organizing principle of modern biology and anthropology. © 2011 The Mc. Graw-Hill Companies, Inc.

7 Evolutionary facts • All living forms come from older or previous living forms

7 Evolutionary facts • All living forms come from older or previous living forms • Birds arose from nonbirds, humans arose from nonhumans, and neither existed 250 million years ago. • Major ancient life forms are now extinct (dinosaurs). • New life forms (viruses) are evolving right now. • Natural processes help us understand the origins and history of plants and animals (including humans and diseases). © 2011 The Mc. Graw-Hill Companies, Inc.

8 Evolution • Humans have uniquely varied ways—cultural and biological—of adapting to environmental stresses

8 Evolution • Humans have uniquely varied ways—cultural and biological—of adapting to environmental stresses • Many scholars became interested in biological diversity and our position within the classification of plants and animals during the 18 th century © 2011 The Mc. Graw-Hill Companies, Inc.

9 Evolution • Creationism: biological similarities and differences originated at the Creation • Based

9 Evolution • Creationism: biological similarities and differences originated at the Creation • Based on Genesis, the first book of Bible • Life forms were seen as immutable, they could not change • Biblical scholars claim to have traced creation to October 23, 4004 BC at 9: 00 am. © 2011 The Mc. Graw-Hill Companies, Inc.

10 Creationism • Linnaeus (1707– 1778) developed the first comprehensive and still influential classification,

10 Creationism • Linnaeus (1707– 1778) developed the first comprehensive and still influential classification, or taxonomy, of plants and animals • He grouped life forms on the basis of differences and similarities in physical characteristics. – Fossil discoveries during the 18 th and 19 th centuries raised doubts about creationism © 2011 The Mc. Graw-Hill Companies, Inc.

11 • If all life originated at the same time, why aren’t ancient species

11 • If all life originated at the same time, why aren’t ancient species still around? • Why weren’t contemporary plants and animals found in fossil records? © 2011 The Mc. Graw-Hill Companies, Inc.

12 Evolution • Catastrophism: a modified version of creationism that accounts for the fossil

12 Evolution • Catastrophism: a modified version of creationism that accounts for the fossil record by positing divinely authored worldwide disasters that wiped out creatures represented in the fossil record © 2011 The Mc. Graw-Hill Companies, Inc.

13 • After each destructive event, God had created again, leading to contemporary species.

13 • After each destructive event, God had created again, leading to contemporary species. • Some ancient species managed to survive in isolated areas, hence the similarities between fossils and modern animals. © 2011 The Mc. Graw-Hill Companies, Inc.

14 Theory and Fact • Evolution (descent with modification): an alternative to creationism and

14 Theory and Fact • Evolution (descent with modification): an alternative to creationism and catastrophism was transformism • Species arise from others through a long and gradual process of transformation. – Charles Darwin is the best known of evolutionists © 2011 The Mc. Graw-Hill Companies, Inc.

15 Theory and Fact • Darwin influenced by – Grandfather, Erasmus Darwin, who proclaimed

15 Theory and Fact • Darwin influenced by – Grandfather, Erasmus Darwin, who proclaimed a common ancestry of all animal species • Lyell’s principle of Uniformitarianism: The present is the key to the past; explanations for past events should be sought in the long-term action of ordinary forces that still operate today. © 2011 The Mc. Graw-Hill Companies, Inc.

16 • Natural forces (rain, earthquakes, volcanic eruptions) have gradually built and modified geological

16 • Natural forces (rain, earthquakes, volcanic eruptions) have gradually built and modified geological features (such as mountain ranges). • Cappadocia © 2011 The Mc. Graw-Hill Companies, Inc.

17 – Uniformitarianism cast doubt on the belief that the world was only 6000

17 – Uniformitarianism cast doubt on the belief that the world was only 6000 years old. It would take much longer for ordinary forces such as rain and wind to produce major geological changes. – Theory of evolution • Theory: a set of ideas formulated to explain something Darwin applied uniformitarianism and long-term transformation to living things and argued that all life forms are related and the number of species have increased over time. © 2011 The Mc. Graw-Hill Companies, Inc.

18 Theory and Fact • Natural selection: the process by which the forms most

18 Theory and Fact • Natural selection: the process by which the forms most suited to survive and reproduce in a given environment do so in greater numbers. • More than survival of the fittest, natural selection is differential reproductive succes. – Competition for strategic resources (food and space) – Finding mates – Variety within that population • Natural selection continues today © 2011 The Mc. Graw-Hill Companies, Inc.

19 Giraffe’s neck • When there’s a food shortage, those with longer necks have

19 Giraffe’s neck • When there’s a food shortage, those with longer necks have an advantage • If this feeding advantagepermits longer-necked giraffes to survive and reproduce more effectively, then they will transmit more of their genetic material to future generations than will those with shorter necks. © 2011 The Mc. Graw-Hill Companies, Inc.

20 Incorrect alternative to Darwinian explanation • Inheritance of acquired characteristics • In each

20 Incorrect alternative to Darwinian explanation • Inheritance of acquired characteristics • In each generation, individual giraffes strain their necks to reach higher and this straining modifies tgeir genetic material. • Over generations of strain , the average giraffe neck gradually gets longer through the accumulation of small increments of neck length acquired during lifetime of each generation of giraffes. © 2011 The Mc. Graw-Hill Companies, Inc.

21 • This is not how evolution works!! • Physical development of the individual,

21 • This is not how evolution works!! • Physical development of the individual, not species. (babies of weight lifters) • Evolution works as the process of natural selectiontakes advantage of the variety that is already present in a population. © 2011 The Mc. Graw-Hill Companies, Inc.

22 Genetics • Genetic science helps us understand the causes of biological variation –

22 Genetics • Genetic science helps us understand the causes of biological variation – Mendelian genetics: studies the ways in which chromosomes transmit genes across generations – Biochemical genetics: examines structure, function, and changes in DNA – Population genetics: investigates natural selection and the causes of genetic variation, stability, and change © 2011 The Mc. Graw-Hill Companies, Inc.

23 Mendel’s Experiments • Austrian monk Gregor Mendel began a series of experiments that

23 Mendel’s Experiments • Austrian monk Gregor Mendel began a series of experiments that revealed the basic principle of genetics in 1856 – Studied inheritance of seven contrasting traits in pea plants – Discovered that heredity is determined by discrete particles or units © 2011 The Mc. Graw-Hill Companies, Inc.

24 Mendel’s Experiments – Concluded that a dominant form could mask another form in

24 Mendel’s Experiments – Concluded that a dominant form could mask another form in hybrid individuals, without destroying the recessive trait – Basic genetic units Mendel described were factors (now called genes or alleles) that are located on chromosomes © 2011 The Mc. Graw-Hill Companies, Inc.

25 Mendel’s Experiments • Chromosome: a paired length of DNA, composed of multiple genes

25 Mendel’s Experiments • Chromosome: a paired length of DNA, composed of multiple genes • Gene: a place (locus) on a chromosome that determines a particular trait • Allele: a variant to a particular gene © 2011 The Mc. Graw-Hill Companies, Inc.

26 Mendel’s Experiments • Heterozygous: dissimilar alleles of a gene in an offspring •

26 Mendel’s Experiments • Heterozygous: dissimilar alleles of a gene in an offspring • Homozygous: two identical alleles of a gene in an offspring – Dominance produces a distinction between genotype (hereditary makeup) and phenotype (expressed physical characteristics) © 2011 The Mc. Graw-Hill Companies, Inc.

27 Mendel’s Experiments • Independent Assortment and Recombination – Independent Assortment: chromosomes are inherited

27 Mendel’s Experiments • Independent Assortment and Recombination – Independent Assortment: chromosomes are inherited independently of one another – Recombination: the combination of genetic traits in an offspring; this process creates new types on which natural selection can operate © 2011 The Mc. Graw-Hill Companies, Inc.

28 Figure 5. 1: Mendel’s Second Set of Experiments with Pea Plants © 2011

28 Figure 5. 1: Mendel’s Second Set of Experiments with Pea Plants © 2011 The Mc. Graw-Hill Companies, Inc.

29 Figure 5. 2: Simplified Representation of a Normal Chromosome Pair © 2011 The

29 Figure 5. 2: Simplified Representation of a Normal Chromosome Pair © 2011 The Mc. Graw-Hill Companies, Inc.

30 Figure 5. 3: Punnett Squares of a Homozygous Cross and a Heterozygous Cross

30 Figure 5. 3: Punnett Squares of a Homozygous Cross and a Heterozygous Cross © 2011 The Mc. Graw-Hill Companies, Inc.

31 Figure 5. 4: Determinants of Phenotypes (Blood Groups) in the ABO System ©

31 Figure 5. 4: Determinants of Phenotypes (Blood Groups) in the ABO System © 2011 The Mc. Graw-Hill Companies, Inc.

32 Biochemical, or Molecular, Genetics • Mutation: changes in the DNA molecules of which

32 Biochemical, or Molecular, Genetics • Mutation: changes in the DNA molecules of which genes and chromosomes are built – Gametes: sex cells that make new generations © 2011 The Mc. Graw-Hill Companies, Inc.

33 Biochemical, or Molecular, Genetics • The DNA molecule is a double helix –

33 Biochemical, or Molecular, Genetics • The DNA molecule is a double helix – RNA carries DNA’s message to its cytoplasm (outer area) – The structure of RNA, with paired bases, matches DNA – DNA, with RNA’s assistance, initiates and guides the construction of hundreds of proteins necessary for bodily growth, maintenance, and repair © 2011 The Mc. Graw-Hill Companies, Inc.

34 Figure 5. 5: A Double-Stranded DNA Molecule © 2011 The Mc. Graw-Hill Companies,

34 Figure 5. 5: A Double-Stranded DNA Molecule © 2011 The Mc. Graw-Hill Companies, Inc.

35 Cell Division • Mitosis: ordinary cell division, wherein one cell splits to form

35 Cell Division • Mitosis: ordinary cell division, wherein one cell splits to form two identical cells • Meiosis: the special process by which sex cells are produced – Four cells – Fertilization allows the produced from one products of meiosis from one parent to – Each cell carries recombine with those half the genetic from the other parent material of the original cell – Chromosomes sort independently © 2011 The Mc. Graw-Hill Companies, Inc.

36 Crossing Over • Crossing over: the process wherein homologous chromosomes exchange segments by

36 Crossing Over • Crossing over: the process wherein homologous chromosomes exchange segments by breakage and recombination – Can occur with any chromosome pair – An important source of variety © 2011 The Mc. Graw-Hill Companies, Inc.

37 Figure 5. 6: Crossing Over © 2011 The Mc. Graw-Hill Companies, Inc.

37 Figure 5. 6: Crossing Over © 2011 The Mc. Graw-Hill Companies, Inc.

38 Mutation • Base substitution mutation: substitution of one base in a triplet by

38 Mutation • Base substitution mutation: substitution of one base in a triplet by another – If mutation occurs in a sex cell, the new organism will carry mutation in every cell • Chromosomal rearrangement: pieces of a chromosome break off and reattach someplace else on that chromosome © 2011 The Mc. Graw-Hill Companies, Inc.

39 Mutation • Approximately three mutations will occur in every sex cell – Most

39 Mutation • Approximately three mutations will occur in every sex cell – Most mutations are neutral – Evolution depends on mutations – Variants produced through mutation can be especially significant if there is a change in environment © 2011 The Mc. Graw-Hill Companies, Inc.

40 Population Genetics and Mechanisms of Genetic Evolution • Population genetics studies stable and

40 Population Genetics and Mechanisms of Genetic Evolution • Population genetics studies stable and changing populations – Gene pool: alleles and genotypes within breeding population – Genetic evolution: the change in allele frequency in a breeding population © 2011 The Mc. Graw-Hill Companies, Inc.

41 Natural Selection • Genotype: the genetic makeup of an organism • Phenotype: an

41 Natural Selection • Genotype: the genetic makeup of an organism • Phenotype: an organism’s evident biological traits – Natural selection acts only on phenotypes – Human biology has considerable plasticity – The environment works on a genotype to build a phenotype © 2011 The Mc. Graw-Hill Companies, Inc.

42 Directional Selection • After several generations of selection, gene frequencies change – Adaptive:

42 Directional Selection • After several generations of selection, gene frequencies change – Adaptive: favored by natural selection – Directional selection continues as long as environmental sources stay the same – Humans do not have to delay adaptation until a favorable mutation occurs © 2011 The Mc. Graw-Hill Companies, Inc.

43 Sexual Selection • Selection also operates through competition for mates – Sexual selection:

43 Sexual Selection • Selection also operates through competition for mates – Sexual selection: based on differential success in mating; a selection of traits that enhances mating success © 2011 The Mc. Graw-Hill Companies, Inc.

44 Stabilizing Selection • Balanced polymorphism: the frequencies of two or more alleles of

44 Stabilizing Selection • Balanced polymorphism: the frequencies of two or more alleles of a gene remain constant from generation to generation © 2011 The Mc. Graw-Hill Companies, Inc.

45 Appreciating Anthropology • Scientists linked the first European explorers of the New World

45 Appreciating Anthropology • Scientists linked the first European explorers of the New World to the origin of sexually transmitted syphilis • Researchers applied phylogenetics in examining 26 geographically disparate strains in the family of treponema bacteria • Infections in the New World have been traced back at least 7, 000 years by studying scars on bones © 2011 The Mc. Graw-Hill Companies, Inc.

46 Random Genetic Drift • Random genetic drift: loss of alleles from a population’s

46 Random Genetic Drift • Random genetic drift: loss of alleles from a population’s gene pool through chance – Lost alleles can reappear in the gene pool only through mutation – Fixation, the replacement, for example, of blue eyes by brown eyes, is more rapid in small populations © 2011 The Mc. Graw-Hill Companies, Inc.

47 Gene Flow • Gene flow: exchange of genetic material between populations of the

47 Gene Flow • Gene flow: exchange of genetic material between populations of the same species – Alleles spread through gene flow even when selection not operating on the allele – Species: group of related organisms whose members can interbreed to produce offspring that live and reproduce – Gene flow tends to prevent speciation: the formation of new species © 2011 The Mc. Graw-Hill Companies, Inc.

48 Figure 5. 8: Gene Flow Between Local Populations © 2011 The Mc. Graw-Hill

48 Figure 5. 8: Gene Flow Between Local Populations © 2011 The Mc. Graw-Hill Companies, Inc.

49 The Modern Synthesis • Currently accepted view of evolution: – Microevolution: small-scale changes

49 The Modern Synthesis • Currently accepted view of evolution: – Microevolution: small-scale changes in allele frequencies over just a few generations – Macroevolution: large-scale changes in allele frequencies in a population over a longer time period that result in the formation of new species. © 2011 The Mc. Graw-Hill Companies, Inc.

50 The Modern Synthesis • Punctuated equilibrium: long periods of stasis may be interrupted

50 The Modern Synthesis • Punctuated equilibrium: long periods of stasis may be interrupted by evolutionary leaps – Sudden environmental change offers possibility for the pace of evolutions to speed up – Although species can survive radical environmental shifts, extinction is more common © 2011 The Mc. Graw-Hill Companies, Inc.