Paleoanthropology - creasonanthro.files.wordpress.comEarliest nonhuman primates resemble ancestral...
Transcript of Paleoanthropology - creasonanthro.files.wordpress.comEarliest nonhuman primates resemble ancestral...
Paleoanthropology-Reconstruct anatomy, behavior, and environment of past hominins
-Includes locating early hominin sites, collecting faunal remains, and artifacts
-Something's date is younger/older than known dates
Stratigraphic dating-Principle that underlying layers are older than overlying layers
Strata: layers of Earth
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Relative dating
-Numerical dates (years, centuries, etc) within a margin of error
Radiometric dating-Unstable isotopes of an element decays into another element
Half-life: measurement based on time it takes an unstable element to decay into another element
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Absolute dating
Carbon dating (dates: 500-75 kya)-5730 year half-life
-Organic materials
-Dates archaeology/recent sites
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Radiometric dating
Potassium/Argon dating (dates: 100 kya-4.6 bya)-1.25 billion year half-life-Volcanism heats rock and releases argon. -Measure amount of Ar-40 in lava/ash = when it was last heated
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Radiometric dating methods
Earliest nonhuman primates resemble ancestral living primates
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Primate fossil record
Paleocene (65-56 mya)-Emerged soon after mammals -Found in North America, Europe, and Asia
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Nonhuman primate fossil record
Eocene (56-34 mya)-Radiation: 200 species emerged (similar to prosimians/tarsiers)-Most extinct by Late Eocene
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Nonhuman primate fossil record
Oligocene (34-23 mya) -Ancestors to modern monkeys
Fayum deposit-Many fossil primates
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Oligocene (34-23 mya)-Ancestors to modern monkeys
Aegyptopithecus-Largest Fayum anthropoid-Significant sexual dimorphism
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Oligocene (34-23 mya)-Ancestors to monkeys
Aegyptopithecus-Largest Fayum anthropoid
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Miocene (23-5 mya)-Golden age of apes (100s of ape species)-Warming trend begins
Proconsul (Africa)-Large-bodied
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Question: What's a hominin?Defining traits-Bipedal-Larger brains-Tool-making behavior
Mosaic evolutionary pattern-Evolution of some traits or functions differ in tempo
Bipedalism: defining hominin trait because the others underwent significant evolutionary changes later
Mosaic evolutionary pattern-Evolution of some traits or functions differ in tempo
Bipedalism: defining hominin trait because the others underwent significant evolutionary changes later
Bipedalism: defining Hominin feature
Hominin bipedalism differs from nonhuman primate locomotion:
Obligate bipeds: most efficient means of locomotion
Habitual bipeds: most common form of locomotion
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Question: Why be bipedal?
Best hypothesis: allows for more energetically efficient locomotion
Bipedal adaptation-Frees hands for carrying things, making/using tools-Bipedal stance gives a wider view of surrounding area-Bipedal walking = efficient way to cover long-distances
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Question: What are anatomical and structural changes in the fossil record showing bipedalism?
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Cranial-Foramen magnum-Spinal curve
Bipedalism - S-curve
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Evidence of bipedalism in the fossil record
PostcranialPelvis: bowl-shaped-Shorter, broader-Extended around the sides
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Evidence of bipedalism in the fossil record
Lower limbs-Long legs, short arms-Diagonal femur
-Provide stability
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Evidence of bipedalism in the fossil record
The foot-Foot arches-Foot stabilizes instead of grasping tree limbs
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Evidence of bipedalism in the fossil record
Pre-Australopiths (7-4.4 mya)
Sahelanthropus 7 myaCentral Africa-Well-preserved cranium-Small-brained (350 cm3) but flat-face
Bipedal?-Position of foramen magnum suggests bipedalism
Pre-Australopiths (7-4.4 mya)
Orrorin 6 myaEast Africa-First potential hominin postcranial remains
Bipedal?-Angle of femur bone suggests bipedalism
Pre-Australopiths (7-4.4 mya)
Ardipithecus5-4 myaEast Africa-Fragmentary to complete skeletons-Derived pelvis-CC = 350 cm3
Bipedal?-Probably but lived in woodland environment
Gracile australopithsAustralopithecus afarensis4-3 myaEast Africa-CC = 420 cm3
-3 ft tall-Ancestor to later hominins
Gracile australopithsAustralopithecus afarensis4-3 myaEast Africa -CC = 420 cm3
-3 ft tall-Ancestor to later hominins
Lucy-40% complete skeleton-Femur bone diagonal
Gracile australopithsAustralopithecus afarensisWhen: 4-3 myaWhere: East Africa (Laetoli for example)-CC = 420 cm3
-3 ft tall-Ancestor to later hominins
Laetoli footprints-Longer digits-Arches
Gracile australopithsAustralopithecus afarensisWhen: 4-3 myaWhere: East Africa (Laetoli for example)-CC = 420 c3-3 ft tall-likely ancestor to later hominins
Laetoli footprints-Longer digits-Arches
Gracile australopiths
Australopithecus africanus3-2 myaSouth Africa-CC = 440 cm3
Taung child
Robust australopiths = Paranthropus
Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones
Robust australopiths = Paranthropus
Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones
Sagittal crest: where jaw muscles attached on cranium
Robust australopiths = Paranthropus
Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones
Sagittal crest: area where jaw muscles attached on cranium
Specialized diet of tough, reedy plants-likely over-specialized and went extinct
Robust australopiths = Paranthropus
Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones
Sagittal crest: area where jaw muscles attached on cranium
Specialized diet of tough, reedy plants-likely over-specialized and went extinct
Early Homo (2.5-1.8 mya)
Homo habilis "Handy-man" 2.5-1.8 myaEast Africa-CC = 630 c3 (20% increase in brain size)
-First hominin associated with stone-tools
Oldowan tool industry (2.6 mya)
-Earliest stone tool industry-Associated with Homo habilis
Flakes -Used to butcher-Disposable
Choppers-Crack bones for marrow
Oldowan tool industry (2.6 mya)
-Earliest stone tool industry-Associated with Homo habilis
Flakes -Used to butcher-Disposable
Choppers-Crack bones for marrow
Early hominins in general
Early hominin derived traits-All bipedal-Genus Homo stone-tool use
Mostly ancestral -smaller-bodies, bigger teeth, smaller brains-tied more to arboreal lifestyle-ape-like accelerated growth and development
Early hominins
Gracile: small-boned or of slight build Refers to characteristics seen in the skull of Australopithecus africanus. A. africanus is similar in some ways to the "robust" species, but lacks their cranial and mandibular adaptations to a dry, hard to chew diet. The characteristics of the "gracile" australopithecines are believed to reflect their diet of softer, easier to chew food items such as fruit, young leaves, and insects.
Early hominins
Robust: Heavier, thick bones and muscles. Refers to characteristics seen in the skulls of three hominin species - Paranthropus aethiopicus and Paranthropus boisei from East Africa, and Paranthropus robustus from South Africa. The characteristics include huge molars and "molarized" premolars, broad cheeks with large zygomatic arches that allow passage of large chewing muscles, and a sagittal crest for attachment of those muscles on the relatively small cranium. The characteristics of the "robust" species are believed to reflect their diet of dry, hard to chew food items such as nuts, roots, tubers, etc.
Gracile: small-boned or of slight build Refers to characteristics seen in the skull of Australopithecus africanus. A. africanus is similar in some ways to the "robust" species, but lacks their cranial and mandibular adaptations to a dry, hard to chew diet. The characteristics of the "gracile" australopithecines are believed to reflect their diet of softer, easier to chew food items such as fruit, young leaves, and insects.