Relative Dating

Digging Up the Past: Paleoanthropology and Archaeology

Lecture Objectives  Identify the importance of fossil in understanding

the behavior and anatomy of ancient hominins.  Identify the differences between paleoanthropology and archaeology.  Compare the similarities and differences between relative and chronometric dating.  Be able to identify and describes examples of relative and chronometric dating.

Paleoanthropology and Fossils

Paleoanthropology  Biological anthropology focus: study of earlier

hominids, including  1.  2.  3.  4.

 Highly _____________

What do paleoanthropologists examine?  FOSSILS  Remember Cuvier – he recognized that fossils were once living organisms  BUT fossils were not important in the realm of science until William Smith (engineering surveyor)

Why Fossils? What information do they hold?  Provide direct ______________  Study of fossil centered on two

factors 

Time 



Environment 

Taphonomy & Fossilization  Commonly bones and

teeth sources (comprise 99 % of fossil record)

 Taphonomy

1.  2. 

Dating Methods

Dating – Why Bother?  Placing sites and fossils into a time frame  Dating techniques

Relative Dating   Chronometric Dating (numerical dating)  What is the numerical age?  Isotope Dating  rate at which various ___________ _____________________________________ 

Relative Dating  Tells the paleoanthropology that something is older or

younger than something else  Does provide:  1.  2.  Does not provide:  1.  2.

Relative Dating #1: Stratigraphy  Study of __________________________  Variety of locations can be compared via chemical, physical and other properties  Law of _______________  Lower stratum (layer) is older than a higher stratum  Problems  Earth distributions  Length of time to accumulate stratum

Relative Dating #2: Biostratigraphy  Employs the associations of fossils in strata to

determine each _________________  Aim is ________________  Why? 

Demonstrates that a particular geological section in one location represents the _______________ as another geological section at some other section

Relative Dating #2: Biostratigraphy

 Index Fossils – _____________________  Example of Irish Elk (died out: 10,600 yBP in

Europe)

Relative Dating #2: Seriation  Typological sequences of artifacts 

Assumption: ___________________ 

Frequency of co-occurrence of artifacts in specific contexts



_____________________ Indicator of ____________________



Relative Dating #2: Seriation  Example: Contextual seriation  Pottery -style rather than function

Numerical Dating  Dating technique that gives an estimate in actual

numbers of years 

_______________________

 We will cover both isotopic and non-isotopic methods:  Radiocarbon  Radiopotassium  Argon-Argon

Numerical Dating #1: Radiometric  Carbon isotopes: Ratio of 14C to 12C is measured  Baseline for start of clock – death of organism  By

calculating the ratio of 14C to 12C one can determine ______________________________

 Used for material younger than 50,000 – not the

best for primate and human evolution 

Archaeologists NOT __________________

Numerical Dating #2: Radiopotassium  Non-organic material (e.g. igneous (volcanic) rock) 

40K

decays slowly from its unstable form to a stable gas, 40Ar  __________________________

 Dates material older than _________________

 Note – cannot date sedimentary rock  First used at ____________________

Numerical Dating #3: Argon-Argon 

40Ar

– 39Ar: volcanic rock is bombarded with “fast” neutrons in a nuclear reactor

 Advantage: ______________________________

• Example: ______________________

Numerical Dating #3: Argon-Argon