Paleoanthropology

[O] Paleoanthropology: Early Hominins #

What is Paleoanthropology? #

• Looks at fossil record of primate evolution
• Try to make evolutionary reconstructions

Methods #

• Geology, paleontology, field sites
• Defining Species: lumpers vs splitters
• Classification: systematic definition of species, phylogenic reconstruction

The Possible First Hominins #

• Sahelanthropus — 7mya, Chad
• Ardipithecus
  • not common ancestor of human/pan, but very close
  • 5–7 mya
• Orrorin — 6mya

Sahelanthropus tchadensis #

• Small brain (similar to chimps)
• More face than brain, flat (orthognathic)
• Thick brow ridge
• “Mosaic fossil” — some shared features
• U-shaped teeth (like chimps)
• Foramen magnum closer to center (bipedal?)

Orrorin tugenensis #

• Thick tooth enamel (ape-like)
• Ape-like canine but small teeth
• Climbing: curved finger/phalanges, humerus muscles → upper arms for locomotion
• Bipedalism: femur muscle marks, thickness, femur neck has even distribution
  • apes have more bone on top

Ardipithecus #

• A. ramidus — recent — 4.4m

• A. kadabba — older — 5.5m

• Lots of specimens — know more about dating, etc

• Presumed descendant of kadabba

• Over 110 specimens from Aramis, Ethiopia

• Reduced canine (no C/P3)

• Lower sexual dimorphism

• Pelvic bone suggests bipedalism

• C/P3 honing complex (canine, premolar, tooth sharpening)

• Toes suggest bipedalism

• reduced canine (no C/P3)

• lower sexual dimorphism

• pelvic bone suggests bipedalism

• toes suggest bipedalism

• mosaic fossil: ape-like toe, in-between pelvic bone

Habitats #

Paleohabitat: mixed ecology environment #

• forest
• grassland
• lakes

Why did hominins appear? #

• Changes in climate: new savannahs, forests breaking up
• Apes adapted to live solely in the forest clumps
• Hominins were able to explore savannah

First Hominin Characteristics #

• Foramen magnum tucked in — upright spine
• Small canines, no sectorial premolar / honing canines
• Flat face (orthognathic)
• Large molar
• 4.2 – 1 mya
• East, South Africa
• Australopithecus (gracile), Paranthropus (robust)

Australopithecus afarensis #

• 3.9 – 3 mya
• Ethiopia, Tanzania (E Africa) ← Hadar, Laetoli sites
• Woodlands habitat (mixed forest/savannah)
• Large faces
• Small brains
• Small canines
• Large premolars, molars
• Similar size + dimorphism to chimps
• most primitive australopithecine
• Bipedal
  • short broad pelvis, bowl-shaped
  • angled femurs
  • short arms
  • aligned big toe
  • footprints preserved in volcanic ash
• Climbing / climbers
  • ribcage more similar to apes (cone shaped)

Australopithecus africanus #

• 3.5 – 2.5 mya

• first australopithecine discovered — “Taung baby” – Raymond Dart, 1925

• South Africa — Sterkfontein, Makapansgat sites

• found in caves

• South Africa — Sterkfontein, Makapansgat sites

• found in caves

Why a separate species from afarensis? #

• large skull (face, brain)
• larger molars, smaller front teeth

Australopithecus garhi #

• 2.5 mya
• Ethiopia (Bouri) — lake/grassland
• mostly bipedal but also arboreal
• prognathic face
• small brain
• evidence of tool use (animal bones w/ cut marks)
• Oldowan tool technology
  • stones from Gona, Ethiopia — crude stones chopped

Paranthropus #

• Later than Australopithecus (2.5–1 mya)
• East/South Africa
• larger face (more muscles)

Traits:

• Larger faces with larger chewing muscles
• Generally larger postcanines than Australopithecus
• Generally smaller front teeth
• Generally larger brains
• More sexual dimorphism
• Similar in postcranial morphology

Paranthropus robustus #

• 2–1 mya
• South Africa

Plant diets

• massive chewing muscles
• large pre/molars
• sagittal keel ← smaller version of crest
• zygomatic arches

Paranthropus boisei #

• 2–1 mya
• Kenya, Ethiopia, Malawi
• lakeside savannah
• Massive face + mandible but very small front teeth
• “megadont” — teeth help eat tough, fibrous food
• Different diet to robustus

Australopithecus sediba #

• very recent discovery
• about 2 mya

Australopithecus sediba #

• very recent discovery
• about 2mya
• smaller body size, longer arms compared to afarensis (more arboreal)
• very similar pelvis to humans
• ape-like ribcage (A-shape)
• gentle zygomatic arch