Natural selection acting on humans

Transcription

1 Natural selection acting on humans 1

2 Natural selection acting on humans 2

3 Natural selection acting on humans 3

4 Geologic time scale Earth's history divided into eras, periods epochs Early Paleozoic era: first vertebrates Late Paleozoic era: mammal-like reptiles diversified and Pangaea formed Continental drift: plate tectonics moved organisms around the globe 4

5 Geologic time scale Continental drift: plate tectonics moved organisms around the globe in the Paleozoic and Mesozoic eras Mesozoic era: age of dinosaurs Cenozoic era: age of mammals 5

6 Macroevolution Macroevolution: larger scale change over geologic time Classification: classify organisms to understand evolutionary relationships Kingdom: Animalia Phyla: Chordata Class: Mammalia Order: Primate Family: Hominidae Genus: Homo Species: sapiens 6

7 Homologies Homologous traits: similarities due to common descent E.g., birds, bats, mice, crocs all have four limbs Contrast with analogies: similarities due to common function 7

8 Two types of homologies Ancestral traits: traits that have been inherited from a remote ancestor Derived traits: traits that have been modified from the ancestral conditions 8

9 Schools of classification Evolutionary systematics phylogenetic trees: -time dimension and -hypothesizes about ancestor-descendant relationships 9

10 Classification Evolutionary Systematics -time dimension -explains ancestor-descendant relationships Cladistics -no time dimension -uses shared derived traits to classify show new species 10

11 Video questions Attendance: Write your name on the paper you use to answer the following questions about the movie. Questions/aims: 1. Name one of the many examples of adaptive radiation from the video 2. Identify at least three examples of the different concepts we've discussed throughout the course: mitosis, meiosis, natural selection, selective pressures, genetic drift, migration, mutation 3. Primates evolved in what geographic location? 11

12 Schools of classification Cladistics derived traits: traits modified from the ancestral condition Clades: lineages that share a common ancestor Anthropologists mostly rely on cladistics 12

13 Classifying biology Question: Which is the most similar? -classify by looking at evolutionary relationships Answer: croc and pigeon 13

14 Macroevolutionary processes Adaptive radiation: rapid expansion and diversification of groups into empty ecological niches Speciation: the emergence of new species Niche: species place in environmental context 14

15 Generalized vs specialized traits Generalized traits are adapted for many functions Specialize when adaptive radiation happens you'll have generalists specialize to niches 15

16 Species concepts Biological species concept: groups of interbreeding individuals that are reproductively isolated Geographically isolated Behaviorally isolated Paleospecies Intraspecific: variation within species Interspecific: variation between species 16

17 Fossils Fossils: any trace of an organism left in a geologic bed Mineralization: rare; the replacement of organic material with inorganic material 17

18 Fossils Fossils: any trace of an organism left in a geologic bed 1. Mineralization: rare; the replacement of organic material with inorganic material 2. Organisms can get trapped in tree resin (amber) 18

19 Fossils Fossils: any trace of an organism left in a geologic bed Mineralization: rare; the replacement of organic material with inorganic material Organisms can get trapped in tree resin (amber) Imprints of tracks or leaves in hardened mud 19

20 Mammalian evolutionary history Late Mesozoic era: earliest mammals Cenozoic era: age of the mammals 20

21 Cretaceous-Tertiary Mass Extinction ~66 mya = Cretaceous-Tertiary or K-T boundary -Large asteroid impacted the Earth caused dramatic changes in the global environment Ex: Plants and plankton could not photosynthesis 75% of plants and animals went extinct -Dinosaurs died off = empty ecological niches 21

22 Modern mammalian subgroups Monotremes: most ancestral mammals, e.g., they lay eggs 22

23 Modern mammalian subgroups Marsupials: immature birth; development continues in mother's pouch 23

24 Modern mammalian subgroups Marsupials: immature birth; development continues in mother's pouch 24

25 Modern mammalian subgroups Placental: in utero development 25

26 Mammalian homologies Endothermic Heterodont dentition Placental Big brained Flexible behavior 26

27 Classifying biology Homologies: similarities based on a common ancestor vs Analogies: similarities due to common function 27

28 Cladistics continued Clades: all the organisms descending from an unknown ancestor -represented in a cladogram E.g., In cladistics, birds would be grouped with dinosaurs 28

29 Fossils Taphonomy: studies how bones and other materials come to be buried in the Earth and preserved as fossils. 29

30 Fossils Fossils are any traces of ancient organisms Taphonomy studies the processes and materials involved in fossilization Fossilization is rare Mineralization: process where the organic materials of an organism are replaced slowly by inorganic materials Traces of organisms trapped in sap Imprints of tracks or leaves left in hardened mud 30

31 Mammalian Evolution Late Mesozoic: earliest mammals Cenozoic Era: diversified Major Mammal Groups *Monotremes: egg-laying = most ancestral *Marsupials: pouched = immature young complete development in external pouch *Placental: long development period in utero and placental tissue specialized to provide nourishment 31

32 Distinctive mammalian homologies Endothermic: mammals are able to internally regulate body temperature Heterodont dentition -Contrast with homodont dentition Placental: in utero development Big brained Flexible behavior 32

33 Fossils preservation Impressions of leafs/things: clay hardens into stone Anthr e.g., 47 mya well preserved primate skeleton with soft-body imprint and fossilized remains associated with the digestive tract (Franzen et al 2009). Footprints from dinosaurs and early Hominins Teeth: hardest, most durable portion of vertebrate skeleton and so most likely to mineralize Most available fossil data is inferred from teeth including primates 33

34 Processes of Macroevolution Adaptive Radiation: rapid expansion and diversification of new life forms into new ecological niches Niche: micro-habitats in nature to which organisms adapt Generalized and Specialized characteristics Generalized: traits that are adapted for many functions Specialized: generalized traits specialize to specific niches

35 Types of variation continued Intraspecific: variation = individual, age, sex differences within species -If variation in fossils compares to related extant organisms, then designate single species Interspecific: such variation represents differences between species Splitters - speciation occurred more often Lumpers - more likely intraspecific variability 35

36 Overview of the primates -native to tropics and semi-tropics Four categories of Primate homologies 1. Limbs and locomotion; 2. Diet and dentition; 3. Senses and brain; 4. Maturity and behavior Rhesus macaque 36

37 Overview of the primates 1. Limbs and locomotion -tendency towards hold their bodies erect -flexible generalized limb structure -prehensile hands and feet -opposable thumbs -nails replace claws on some digits -tactile pads on digits 37

38 Overview of the primates 2. Diet and dentition -generalized; omnivorous Dental formulas: 38

39 Overview of the primates 3. Senses and brain -color vision and diurnal -stereoscopic vision - eyes are located in front of face -decreased reliance on sense of smell 39

40 Overview of the primates 4. Maturity and behavior -long life span -long gestation period -few offspring -delayed maturation Behavior -depend more on learned, flexible behavior over pre-packaged instinct -highly social 40

41 Three hypotheses explaining primate adaptations Question: can we reconstruct the environment primates adapted to to explain their defining traits? Arboreal hypothesis: many primate traits are adaptations to living in trees Visual-predation hypothesis: many primate traits are adaptations to hunting insects in the lower tiers of the rainforests mya. Flowering plant hypothesis: primate traits developed the same time flowering plants (angiosperms) diversified globally. 41

42 Survey of living primates Lemurs and lorises - suborder Strepsirhini -most ancestral Shared characteristics -reliance on olfaction (ancestrall) rhinarium: moist, fleshy pad on noses -shorter gestation/maturation period -specialization: dental comb: used to groom and feed 42

43 Survey of living primates Lemurs and lorises - suborder Strepsirhini -most ancestral -Madagascar large lemurs: diurnal (derived); smaller lemurs: nocturnal insectivores (ancestral) Lemurs get high 43

44 Tarsiers Southeast Asia islands Shared characteristics -nocturnal -insectivores -enormous immobile eyes -head can rotate 180 degrees 44

45 Anthropoids: monkeys apes, humans Traits shared by all anthropoids -larger body and brain -increased reliance on vision -longer gestation and maturation periods -increased parental care -more mutual grooming 45

46 Anthropoids: monkeys apes, humans Monkeys: 85% of all primate species Two groups divided geographically: New World monkeys and Old World monkeys New World Monkeys Found in Central and South America -all are diurnal (except owl monkeys) -almost exclusively arboreal 46

47 Anthropoids: monkeys apes, humans Tamarins and marmosets: smallest monkeys -claws -twin births -mated pairs: social group -males more involved in infant care 47

48 Anthropoids: monkeys apes, humans Old World Monkeys -tropical forests to semiarid deserts -most are quadrupedal All belong to Cercopithecidae family -subfamilies: Cecropithecinae and Colobinae -mostly arboreal; some spend more time on ground -sexual dimorphism, e.g., females during estrus have swelling and redness 48

49 Anthropoids: monkeys apes, humans Old World Monkeys Cercopithecines: baboons and macaques -omnivorous -mostly in Africa (except macaques) Ischial Callosities: tough leathery pad cercopithecines on their hindquarters 49

50 Anthropoids: monkeys apes, humans Old World Monkeys Colobines: African colobus monkeys and Asian langurs -narrower diet of eat mainly leaves Segmented stomachs aid in digesting leaves more efficiently 50

51 Hominoids - apes and humans Characteristics distinguishing hominoids from monkeys -larger body size -shortened trunk (more stable lower back) -no tail -arms longer than legs (except in humans) -more complex behavior and brain -increased period of infant development -omnivorous 51

52 Hominoids - apes and humans Gibbons -fastest brachiators -curved fingers, muscled shoulders Orangutans Borneo and Sumatra Characteristics -almost completely arboreal -sexual dimorphism 52

53 Hominoids - apes and humans Gorillas Africa: eastern lowland, western lowland, and mountain gorillas Characteristics -largest primates -primarily terrestrial -'knuckle-walkers' sexual dimorphism: 400 pound males vs 200 pound females Social organization: natal group -vegetarian 53

54 Hominoids - chimpanzees Chimpanzees -equatorial Africa Characteristics -anatomically similar to gorillas -knuckle-walking on ground, brachiation in trees Diet: variety of plants and animal foods Social: large fluid communities; form lifelong attachments 54

55 Hominoids - bonobos Bonobos Areas south of Zaire River Characteristics ~chimpanzees only less sexual dimorphism -includes frequent copulations throughout female estrous cycle -stable male-female bonding -more frequent sexual activity and sexual activity between members of the same sex 55

56 Hominoids - humans Scientific name for our species: Homo sapiens -italicize -Genus is capitalized -species lowercase 56

57 Hominoids - humans Found everywhere in all climates -generalized features like the other apes -omnivorous Characteristics -only living bipeds -entirely dependent on culture -brainsize increased enormously 57