Announcements. Today. Chapter 8 primate and hominin origins. Keep in mind. Quiz 2: Wednesday/Thursday May 15/16 (week 14)

Transcription

1 Announcements Today Chapter 8 primate and hominin origins Keep in mind Quiz 2: Wednesday/Thursday May 15/16 (week 14) Essay 2: Questions are up on course website 1

2 Recap the main points of ch 6 and 7 Evolutionary trends Important traits and behaviors observed in living primate populations help us studying primate evolution E.g., earliest primate fossils resembled lemurs and tarsiers who are the most ancestral primates Modern primates: Know habitat, diet, morphology, social structure, behaviors Primates in the fossil record: Infer similar interactions between these influences held for our ancestors too. 2

3 Geologic record of the primates to us Cenozoic Era has several important epochs for primate evolutionary history Paleocene 65 mya Age of the mammals Changes in primate locations coincide with the history of climate change over the past 60 years 3

4 Geologic record of the primates to us Eocene 55 mya Earliest primates - resembled modern day lemurs and tarsiers Found in North America, Europe, and Asia - all connected at the time 4

5 Geologic record of the primates to us Eocene 55 mya Earliest primates - resembled modern day lemurs and tarsiers Found in North America, Europe, and Asia - all connected at the time Oligocene 34 mya Fayum primates Aegyptopithecus spp Fayum sight in Egypt Significant sexual dimorphism 5

6 Geologic record of the primates to us Miocene 23 mya Golden age of apes - 100s of ape species Warming trend begins Proconsul spp -hominoid found geographically widespread throughout Africa -large-bodied 6

7 Dating methods Fossil dating - two methods Relative dating: gives dates are relative to known dates -stratigraphy and law of superposition Say this fossil is older or more recent relative to fossils found in other layers 7

8 Dating methods Fossil dating - two methods Relative dating: Earth's stratigraphy dates are relative to known dates Absolute dating: gives us temporal ages (years, decades, etc) -dating method using decay of isotopes with known rates of change can Carbon 14: kya Half life: 5730 years Dates organic materials Potassium-Argon: 100k bya Dates volcanic rock 8

9 Dating methods Fossil dating - two methods Relative dating: Earth's stratigraphy dates are relative to known dates Absolute dating: dating method using decay of isotopes with known rates of change can give us temporal ages (years, decades, etc) Carbon 14: kya Half life: 5730 years Dates organic materials Potassium-Argon: 100k bya Dates volcanic rock 9

10 Paleoanthropology -study of early humans. -Includes locating early hominin sites, collecting faunal remains, and artifacts -reconstruct the anatomy, behavior, and ecology of our ancestors

11 Geologic record of the primates to us Question: What are differences between us and the nonhuman primates that we can find in the fossil record? 11

12 Geologic record of the primates to us Question: Why be bipedal? 12

13 Geologic record of the primates to us Question: Why be bipedal? Best hypothesis so far: allowed for more energetically efficient locomotion Recall: the late Miocene: drier climate and forests became patchier 13

14 Bipedalism - Defining Hominin feature Hominin bipedalism differs from nonhuman primate locomotion in two ways: Obligate bipeds: most efficient mode of locomotion Habitual bipeds: most common form of locomotion 14

15 Geologic record of the primates to us Evidence of bipedalism in the fossil record -Foramen magnum -spinal curve 15

16 Geologic record of the primates to us Evidence of bipedalism in the fossil record -Foramen magnum -spinal curve 16

17 Geologic record of the primates to us Evidence of bipedalism in the fossil record -short wide hips -bowl-shaped pelvis 17

18 Geologic record of the primates to us Evidence of bipedalism in the fossil record -long legs, short arms -diagonal femur 18

19 Geologic record of the primates to us Evidence of bipedalism in the fossil record -foot arches -foot used to stabilize instead of grasping tree limbs 19

20 Geologic record of the primates to us Evidence of bipedalism in the fossil record -Foramen magnum -spinal curve -short wide hips -long legs, short arms -diagonal femur -foot arches 20

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22 First possible hominin Sahelanthropus - first possible hominin ~6 mya Found in Chad, central Africa Brain size: 350 cc ~ chimp size

23 First possible hominin Sahelanthropus - first possible hominin ~6 mya Found in Chad, central Africa Brain size: 350 cc ~ chimp size Bipedal? Position of the foramen magnum suggests bipedalism

24 Pliocene epoch mya -Hominin diversification -Variability in climate Epoch features two important hominin genera Australopithecus and Paranthropus

25 Australopiths Genus Australopithecus - first hominins i.e., definitely bipedal Gracile hominins Characterized by small brain, bipedalism, and big teeth -resembled our ancestors more than modern humans

26 Representative australopiths Australopithecus afarensis 4-3 mya East Africa (several sites) Brain size: 420 cc (larger than chimpanzee) Notable specimens/fossils Lucy Laetoli footprints

27 Representative australopiths Australopithecus afarensis 4-3 mya East Africa (several sites) Brain size: 420 cc (larger than chimpanzee) Notable specimens/fossils Lucy Laetoli footprints

28 Representative australopiths Australopithecus afarensis Laetoli footprints

29 Representative australopiths Australopithecus africanus mya South Africa Brain size: 485 cc Notable specimens/fossils Taung child - skull and brain preserved in brain cast

30 Genus Paranthropus General features -bipedal -robust -gorilla-sized -adaptations specializing to niche diet Diet ~ panda diet of bamboo -probably ate dense reedy plant

31 Representative Paranthropus Paranthropus aethiopicus ~2.4 mya East Africa Note: sagittal crest similar to gorilla

32 Representative Paranthropus Paranthropus boisei mya South Africa Brain size: 520 cc Note: -likely descendant of P. aethiopicus -last robust species - over committed to specialized niche

33 Representative Paranthropus Paranthropus boisei mya South Africa Brain size: 520 cc Note: -likely descendant of P. aethiopicus -last robust species - over committed to specialized niche

34 Genus Homo -probably descended from gracile australopiths -early species resembled the australopiths in characteristics Distinguishing characteristic: tool use Homo habilis - 'handy man' 2.4 mya East Africa Brain size: 631 cc Tool use: Oldowan tool industry

35 First stone tools Oldowan tool industry ~2.6 mya earliest stone tools -sites of Homo featured scattered tools, debris, butchered animal bones *Choppers - used to crack bones to access bone marrow (rich nutritional source) *Flakes - disposable - used to butcher

36 A Tentative Early Hominin Phylogeny