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Natural selection acting on humans
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Natural selection acting on humans
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Natural selection acting on humans
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Geologic time scaleEarth'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
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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
MacroevolutionMacroevolution: larger scale change over geologic time
Classification: classify organisms to understand evolutionary relationships
Kingdom: AnimaliaPhyla: Chordata
Class: MammaliaOrder: Primate
Family: HominidaeGenus: Homo
Species: sapiens
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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
Two types of homologiesAncestral traits: traits that have been inherited from a remote ancestor
Derived traits: traits that have been modified from the ancestral conditions
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Schools of classificationEvolutionary systematics
phylogenetic trees: -time dimension and -hypothesizes about ancestor-descendant relationships
Evolutionary Systematics-time dimension-explains ancestor-descendant relationships
Cladistics-no time dimension-uses shared derived traits to classify show new species
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Classification
Video questionsAttendance: 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?
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Schools of classification
Cladistics
derived traits: traits modified from the ancestral condition
Clades: lineages that share a common ancestor
Anthropologists mostly rely on cladistics
Classifying biologyQuestion: Which is the most similar?
-classify by looking at evolutionary relationships
Answer: croc and pigeon
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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
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Generalized vs specialized traitsGeneralized traits are adapted for many functions
Specialize when adaptive radiation happens you'll have generalists specialize to niches
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Species concepts
Biological species concept: groups of interbreeding individuals that are reproductively isolated
Geographically isolatedBehaviorally isolated
Paleospecies
Intraspecific: variation within speciesInterspecific: variation between species
Fossils: any trace of an organism left in a geologic bed
Mineralization: rare; the replacement of organic material with inorganic material
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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)
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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
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Fossils
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Mammalian evolutionary history
Late Mesozoic era: earliest mammals
Cenozoic era: age of the mammals
Cretaceous-Tertiary Mass Extinction~66 mya = Cretaceous-Tertiary or K-T boundary
-Large asteroid impacted the Earth caused dramatic changes in the global environmentEx: Plants and plankton could not photosynthesis
75% of plants and animals went extinct
-Dinosaurs died off = empty ecological niches
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Modern mammalian subgroupsMonotremes: most ancestral mammals, e.g., they lay eggs
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Modern mammalian subgroupsMarsupials: immature birth; development continues in mother's pouch
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Modern mammalian subgroupsMarsupials: immature birth; development continues in mother's pouch
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Modern mammalian subgroupsPlacental: in utero development
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Mammalian homologiesEndothermic
Heterodont dentition
Placental
Big brained
Flexible behavior
Classifying biologyHomologies: similarities based on a common ancestor
vs
Analogies: similarities due to common function
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Clades: all the organisms descending from an unknown ancestor-represented in a cladogram
E.g., In cladistics, birds would be grouped with dinosaurs
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Cladistics continued
Taphonomy: studies how bones and other materials come to be buried in the Earth and preserved as fossils.
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Fossils
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FossilsFossils 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
Late Mesozoic: earliest mammalsCenozoic 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
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Mammalian Evolution
Distinctive mammalian homologiesEndothermic: mammals are able to internally regulate body temperature
Heterodont dentition-Contrast with homodont dentition
Placental: in utero development
Big brained
Flexible behavior
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Fossils preservationImpressions of leafs/things: clay hardens into stoneAnthr 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
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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
https://youtu.be/Zon4Cc77YFw
https://youtu.be/StqZI9pMq0U
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Processes of Macroevolution
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
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Types of variation continued
-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
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Overview of the primates
Rhesus macaque
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
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Overview of the primates
2. Diet and dentition
-generalized; omnivorous
Dental formulas:
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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
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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
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Overview of the primates
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.
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Three hypotheses explaining primate adaptations
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
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Survey of living primates
Lemurs and lorises - suborder Strepsirhini-most ancestral
-Madagascar
large lemurs: diurnal (derived);
smaller lemurs: nocturnal insectivores (ancestral)
Lemurs get highhttps://youtu.be/-LwQ0ZiTYkQ
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Survey of living primates
Southeast Asia islands
Shared characteristics
-nocturnal
-insectivores
https://youtu.be/gGsKDjvwVM8
-enormous immobile eyes
-head can rotate 180 degrees
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Tarsiers
Traits shared by all anthropoids
-larger body and brain
-increased reliance on vision
-longer gestation and maturation periods
-increased parental care
-more mutual grooming
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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
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Anthropoids: monkeys apes, humans
Tamarins and marmosets: smallest monkeys
-claws
-twin births
-mated pairs: social group
-males more involved in infant care
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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
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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
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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
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Anthropoids: monkeys apes, 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
-omnivorous51
Hominoids - apes and humans
Gibbons-fastest brachiatorshttps://youtu.be/U3JhwjNfx_g-curved fingers, muscled shoulders
OrangutansBorneo and SumatraCharacteristics-almost completely arboreal-sexual dimorphism
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Hominoids - apes and humans
GorillasAfrica: 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
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Hominoids - apes and humans
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
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Hominoids - chimpanzees
BonobosAreas 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
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Hominoids - bonobos
Scientific name for our species:
Homo sapiens
-italicize-Genus is capitalized -species lowercase
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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
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Hominoids - humans
