Lecture 7: Plio-Pleistocene Hominids

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Def. of Homind

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-any member of "the great apes"
-earliest evidence of hominid= miocene
-humans are distingushed from great apes by obvious features

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Plio-Pleistocene

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-first half of pliocene
-5-1 mya
-numerous fossil hominids found in africa
-presence of bipedalism in the fossil record without a savannah environment shows bipedalism appeared without any particular adaptive benefits; but through RANDOM MACROMUTATION

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Mosaic Evolution Theory

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-the rates of evolution in one system vary from other systems
-in hominid evolution, the dental system, locomotor system, and neurology system all eveolved at different rates

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Mosaic Evolution of Modern Homo Sapiens

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-Bipedal
-shortened pelvis
-larger body size
-legs longer
-fingers and toes shorter

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Mosaic Evolution on Early Hominids

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-bipedal
-smaller body size
-long arms relative to legs
-long digits
-capable of lots of climbing

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Mosaic Evolution of Generalized hominoids

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-Quadrupedal
-long pelvis
-arm swinging
-suspensory locomotion

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8 factors influencing the initial evolution of bipedal locomotion

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1. carrying (freed arms)
2. hunting (new)
3. seed and nut gathering (standing upright)
4. feeding from bushes (posture)
5. Thermoregulation (cooling)
6. Visual surveillance
7. Long-distance walking
8. Male provisioning (carry shit to dependent women/kids)

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obligate bipedalism

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since major anatomical changes in spine, pelvis, and lower limbs are required for bipedal locomotion, once hominids adapted, it was the only possible way of locomotion.

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foramen magnum

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-occipital bone at base of skull
-major feature of bipedalism
-more forward position in human, so head is balanced on spine

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Major features of Hominid Bipedalism

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-foramen magnum
-2 curves in spine- a backward (thoracic) and forward (lumbar) curve that keep the trunk centered above pelvis
-human pelvis = basin
-ossa coxae-shorter, broader
-human lower limbs elongated
-femur angles in, keeing legs directly beneath body.
-big toe

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Olduvai Gorge Site

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-Louis & Mary Leakey
-continuous excavations 1930-1980
-150 extinct animals
-gives us clues to early hominid habitats

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Zinjanthropus

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-cranium discovered by Mary Leakey at Olduvai Gorge 1959
-part of genus paranthropus

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excavations at olduvai

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-site over 1 million years old
-located when a hominid arm bone was found eroding on outside of gorge

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Remains at olduvai

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-scatter of stone, and fossilized animal bone from about 1.6 mya.
-some of these remains are result of hominid activities

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Middle Awash

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-very early hominid discovery
-Ethiopia; five localities
-ardipithicus

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Aramis

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in ethiopia (E.Africa)

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Australipithecus

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-early hominid genus
-from plio-pleistocene
-characterized by bipedal locomotion, realtively small brain, large back teeth

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Australipithecine

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-name for members of genus Australipithecus and Paranthropus

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Features of Australipithecus

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--all bipedal
-relatively small brains
--large back teeth

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Lucy

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-partial hominid skeleton discovered at Hadar (ethiopia) in 1974
-Australipithecus afarensis
-paleontologists reconstructed the entire skeleton from remains that were discovered
-40% complete skeleton of "lucy" indicates that australopithecine ancestors were bipedal
-adult femal, only about 3 and a half feet tall.

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Laetoli Site

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-Dated between 3.5 and 3.7 mya
-fossilized hominid footprints found
-found that the individuals were bipedal; some argue not in the same way as modern humans

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Hadar Site (afar triangle)

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3.9-2.3 mya
Recovered:
-lucy
-group of bones representing 13 individuals, including 4 infants, suggesting they all died at the same time
-stone tools may be 2.5 myo, making the the oldest cultural evidence

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Koobi fora Site (East Lake Turkana)

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-site yielded the richest assemblage of Plio-Pleistocene hominids from Africa
-hominids date back to 3.3 to 1.8 mya
-150 hominid specimins recovered, at least 100 individuals

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West Turkana Site

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2 important discoveries:
-nearly complete 1.6 mya homo erectus adolescent
-"the black skull"-a well-preserved 2.4 myo skull

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S. African sites

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-first autralipithecine = "the missing link" b/w apes and humans was discovered at TAUNG
-acceptance of australopithecines as hominids required revision of human evolutionary theory

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Taung Child

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-Discoveries in 1924
-first australipithecine found
-Australopithecus africanus
--endocast in black, with fossilized bone mandible and face in front

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Homo habilis

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-species of early homo, well known from east africa, but perhaps found in other regions

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Groups of Plio-PLeistocene hominids

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-specimins of 200 individuals from S. africa and more than 300 from E. Africa
Divided into 4 borad groupings

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Methodical steps in interpreting Hominid Evolutionary Events

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1. selecting and surveying sites
2. excavating sites and recovering fossil hominids
3. pairing find with number for reference
4. cleaning, preparing, studying, describing fossil
5. comparing with other fossil material
6. comparing fossil variation
7. assigning taxonomic names to fossil material