PALEONTOLOGY: KEY QUESTIONS

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PALEONTOLOGY KEY QUESTIONS

• How do we locate, recover, and date fossil
  remains?
• What are the features of the primate skeleton,
  and how can our knowledge of them help us
  identify fossil remains?

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THE FOSSIL RECORD PRESERVATION

• Not a representative sample of all of the species
  that have lived on earth
• Some species and body parts preserve better than
  others
• TAPHONOMY study of the processes that affect
  the remains of dead animals

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THE FOSSIL RECORD FINDING FOSSILS

• More likely to be found in areas with little
  vegetation and lots of erosion (i.e. lake
  bottoms)
• Due to issues regarding the preservation and
  discovery of fossils, the fossil record of early
  primates is limited and spotty

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DATING CONCEPTS

• PALEONTOLOGY study of ancient life through the
  fossil record
• Anthropology Paleontology --interested in
  establishing a chronology for primate and human
  evolution
• Much dating depends on STRATIGRAPHY study of
  the sequence of geographical layers

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RELATIVE DATING

• Uses natural layers or strata to establish a
  relative chronologymaterial from this layer is
  older than the material from that layer
• Association with known fossils, biostratigraphy
  most common method of fossil dating

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ABSOLUTE DATING (p.202!)

• Produce dates in years, so differences in age can
  be quantified
• Radiometric techniques based on known rates of
  radioactive decay in elements found in or around
  fossils
• Radiocarbon (Half-life of 14C is 5,730 yrs.),
  dates organic remains from 100s to 40,000 ya
  (half life time needed for ½ amount of 14C to
  decay)
• Potassium Argon (K/A) dates volcanic rock from
  100,000 to billions ya

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ABSOLUTE DATING

• Electron Spin Resonance (ESR) Measures of
  electrons excited to higher energy levels by
  natural radiation trapped at those levels,
  dates teeth cave deposits from 100s to 10 mya
• Luminescence Same as ESR, but trapped energy is
  released using heat or light, dates pottery,
  bricks, burned rock up to 800,000 ya

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Hypothetical Stratigraphic Sequence

• IF Humanlike remains were found between two
  layers of volcanic rock, how could we date the
  remains?
• K/Ar (potassium/argon) dating
• Remains are younger than the volcanic deposit
  below and older than the one above

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Absolute Dating Techniques
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Continents At End of the Mesozoic
Placement of the continents at the end of the
Mesozoic and beginning of the Cenozoic, about 65
mya
Tethys Seaway
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Cenozoic Timescale
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Taphonomy

• Leopard remains of early hominid in tree above
  entrance to cave
• Accumulation of bones, including hominid bones,
  in South African caves
• Bones, antlers, teeth found in the caves once
  thought to be early tools used by bipedal killer
  apes to hunt and forage
• Taphonomic research now shows that they are a
  natural accumulation the killer apes were
  prey not predator!

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Skeletal Anatomy

• Skeletons of
• Modern Human
• Gorilla
• Domestic Cat

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Comparative Primate Anatomy
Differences in stance Indri Vertical clinging
and leaping Macaque Generalized
quadrupedalism Gorilla Semi-erect knuckle
walking Chimp Knuckle-walking and tree
climbing Human Fully erect bipedalism
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Cranial Anatomy

• Hominoid primates share same overall
  construction of the skull
• Proportions of the various bones of the skull,
  however, vary, as do the expression of various
  ridge-like features on surface of the bone
• What do you think are some of the reasons for
  these differences?

Brow ridge
Sagittal crest
Frontal
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Axial Skeleton (Trunk) of OW Primates
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Changes in the anatomy of the trunk
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Hominoid Comparative Anatomy
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Changes in Human Skeleton

• Skull more balanced on spine
• Smaller neck muscles
• Spine articulates under skull
• Multiple curves of spine
• Narrower rib cage

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Changes in Human Skeleton (cont.)

• Shorter wider pelvis
• Proportionately longer legs
• Upper leg angled inward so knees closer to
  midline
• Big toe in line with other toes
• Center of gravity in pelvic basin

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