Download Lecture on Chapter 3

Lecture on Chapter 3
Objective
• Understanding the nature and the antiquity of hominin fossil record
and having an appreciation of various disciplines that contribute to the
field of paleoanthropology
What do Paleoanthropologists do?
• Collecting and interpreting
fossil hominins
• Establishing how and where
fossils are found
• Establishing the antiquities of
the fossil record
• Reconstructing fossil
hominin paleobiology
• Classifying the hominin
fossil record
• Establishing the tempo and
mode of human evolution
How do remains become incorporated into the
geologic record?
Fossilization process and recovery
Organism dies or
sheds body parts
NECROLOGY
Organic (soft tissue)
parts decay
Sedimentary process
interact with
remaining (inorganic)
parts
BIOSTRATINOMY
Processes that occur between the
death of an organism and its
subsequent burial in the sediment
are termed biostratinomy.
Burial process
Chemical alteration
and lithification
Recovery/collection
process
DIAGENESIS
The physical and/or chemical
effects after burial are called
diagenesis.
What types of environments are Ideal for
fossilization process?
A
C
B
D
What is paleoecology?
A study of past ecological settings using proxy data
• Ecology
• Source: currently living
organisms in an intact
ecosystem
• Precise and comprehensive
description of environments
and organism in an ecosystem
• Potentially all faunal and floral
components are available in the
observed biocenosis
• Paleoecology
• Source: Fossil assemblages
• Mostly characterization of a
former milieu: making
inferences on environmental
and organismic fact
• Fossils are the only data
available (nature of the fossil
record)
Paleoecological research
• Aims
• at analyzing long-term past ecological trends (development of communities
in certain environments)
• Understanding
• Antemortem events: all processes that affected a fossil organism
• Postmortem events: taphonomic approach studying diagenesis
Linking the past & present
After Foley (1987)
Things to consider in paleoecological studies
after Hardt et al. 2007
Terms
• Biocoenosis:
• group of co-occurring live organisms
• Thanatocoenosis:
• group of co-occurring dead organisms
Bone assemblage analyses
• Characterizing the vertebrate accumulations
• How did the assemblage form
• Taphonomic characteristics of the assemblage
• Identifications
• counts of taxa and body parts
•
•
•
•
•
Number of specimens
Number of individuals
Number of species
Relative abundance of species
Body size, age spectra
• mapping of spatial arrays of bones in situ
• Skeletal articulation
• Representation of skeletal parts
• Size of bone accumulation, spatial density, pattern of arrangement
• description of bone modification
Locating paleoanthropological sites
How are sites found/established?
 Systematic surface surveys and
reconnaissance
 Remote sensing: satellite imaging and
ground penetrating radar
How do we recover
paleoanthropological remains?
 Excavations
 Surface collections: 100% surface
collection
Some fossil faunal remains from Localities 8 and 9, Upper Laetolil Beds.
Locality 8
25.0
% MNE
20.0
15.0
10.0
Vertebrae
Tibiae
Teeth
Scapulae
Ribs
Radius
Phalanges
Pelvis
Metapodials
Mandibles
Humeri
Femora
Horncores
Locality 9
Calcanei
Tali
0.0
Skull
5.0
Skeletal parts
Fossil bone distribution and orientation pattern at Localities 8 and 9 Upper
Laetolil Beds
Importance of Stratigraphy in Paleoanthropology
• A study of how strata (sediment layers)
form and become deposited
• Charles Lyell: Principles of
Stratigraphy
• Steno’s Principle of original
horizontality
• Steno’s Principle of superposition
• Hutton’s Principle of cross-cutting
relationships
• Smith’s Principle of faunal
succession
• Index fossils
• First appearance
• Last appearance
• Hutton and the Concept of
Uniformitarianism
How do we know the age of archaeological
or paleoanthropological remains?
Anthropologists rely on
geochronologists for dating
process of sediments and
artifacts
 An accurate time scale in
paleoanthropology is very crucial for
the understanding the evolutionary
history of our species.
 The appreciation of reliable methods of
dating has the potentials to radically
alter interpretations of evolutionary
relationships.
Example of a stratigraphic correlation placing fossils in relative
and absolute age
Stratigraphic profile at Olduvai Gorge, Tanzania
The Caves of Malapa, South Africa
The Caves of Malapa, South Africa
Establishing the Antiquity of the finds

There are two ways in which paleoanthropologists may choose to determine the
age of any finds
1.
Relative Dating Methods
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•
•
2.
Calibrated Relative Dating Methods (correlated to absolute
chronology)
•
•
•
1.
Lithostratigraphy – correlation of rocks characteristics over a large
region
Tephrostratigraphy – correlation on the basis of tephra (volcanic ash)
Biostratigraphy – correlation based on fauna succession and their
evolutionary history
Obsidian hydration
Amino acid racemization
Paleomagnetism (use of geomagnetic polarity time scale)
Chemical techniques
• F-U-N trio (Fluorine, Uranium, and Nitrogen) in bone remains
Chronometric or Absolute Dating Method
• A technique that utilizes radioisotopic calibration of
different elements such as Carbon (C), Potassium (K),
and Argon (Ar)
• The method exploits some aspects of radioactive decay
of K and Ar, where initially an action sets the clock to
zero
• Such as heating of a rock containing Ar during volcanic
eruption, then radioactive decay steadily accumulates, thus
recording the passage of time.
Methods used in chronometric dating
• Potassium-Argon (K40/Ar40)
• Argon-Argon (Ar39/Ar40 )
• Fission-Track on volcanic glass particularly in
Uranium series (Ur238/Ur239)
• Thermoluminescence (TL) such as in quartz and
feldspar minerals
• Electron Spin Resonance (ESR) – e.g. on tooth
enamels
• Radiocarbon (C14) decay: ratio of C12 to C14
• Amino acid racemization (L-amino  D-amino acids
ratios over time)
Advancement in dating methods  SCLF techniques
Geomagnetic polarity
• Paleomagnetic dating of earth’s geomagnetic polarity time scale
(GPTS)
• Measures changes in periodicity and intensity of earth’s magnetic field
• Changes usually take place about 5,000 years to occur
• They are measured as either normal or reversed polarity events