or how to make sense out of ch. 8 of the text... prehistoric cultures tim roufs section ©2009 class...
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. . . or how to make sense
out of
Ch. 8 of the text . . .
Prehistoric Cultures
Tim Roufs’ section ©2009
Class Slides Set 10A
Special Skills Used to Study Early Humans
ArchaeologicalArchaeological
DatingDating
MethodsMethods
In the Field and LabIn the Field and Lab
techniques =
specific tools / procedures used
methods =basic overall approaches to a
problem
In the Field and LabIn the Field and Lab
archaeological dating methods
1. relative dating2. chronometric dating
(aka “absolute” dating)
Relative and Chronometric DatingUnderstanding Humans, 10th Ed., p. 189.
Understanding Humans, 10th Ed., p. 188.
REM: relative
methods
tell you whether something is
older / younger / the same age
methods
Understanding Humans, 10th Ed., p. 188.
REM: chronometric
methods
yield yield a date
often scaled in calendar years
Michels, Dating Methods in Archaeology, p. 4.
Relative and “Absolute” (Chronometric) Dating Techniques.
method technique
People of the Earth, 10th Ed., p. 11.
technique
techniques
In the Field and LabIn the Field and Lab
stratigraphy
the sequence of geological strata, or layers, formed by materials deposited by
water or wind
also the study of this sequence
Understanding Humans, 10th Ed., p. 188.
REM: relative
methods
tell you whether something is
older / younger / the same age
Humankind Emerging, 7th Ed., p. 24.
People of the Earth, p. 18.
Main gorge at Olduvai. Note geological beds.Understanding Humans, 10th Ed., p. 197.
Hoebel, Anthropology: The Study of Man and Archaeology, 4th Ed., p. 153.
Olduvai Gorge, Kenya.
Bed I
In the Field and LabIn the Field and Lab
archaeological dating methods
1. relative dating2. chronometric dating
(aka “absolute” dating)
In the Field and LabIn the Field and Lab
archaeological dating methods
2. chronometric dating (aka “absolute” dating)
provides estimates in actual numbers of years (sometimes +/-)
Relative and Chronometric Dating
Understanding Humans, 10th Ed., p. 189.
In the Field and LabIn the Field and Lab
2. chronometric dating (aka “absolute” dating)
determining the actual age of geological deposits (and the fossils in them) by examining the chemical composition of rock fragments and organic remains containing radioactive substances such as uranium 238, and carbon 14, which decay at a known rate
archaeological dating methods
In the Field and LabIn the Field and Lab
A.1. or “First Order Absolute Dating”
direct determination of age based on internal evidence
e.g., 14C dating of bone samplee.g., dendrochronologye.g., molecular clocks
Relative and Chronometric Dating
Understanding Humans, 10th Ed., p. 189.
Technician in a radiocarbon dating laboratory.
Understanding Humans, 10th Ed., p. 194.
Radiocarbon dating:
• method was developed in the
1940’s by Willard Libby and a team of
scientists at the University of
Chicago.
•Very powerful in dating artifacts and
geological events up to about 50,000
years ago.
Radiocarbon dating relies on a simple natural phenomenon. As the earth’s upper
atmosphere is bombarded by cosmic radiation, atmospheric nitrogen is broken
down into an unstable isotope of carbon– carbon 14 (C-14).
Because it reacts identically to C-12 and C-13, C-14 becomes attached to
complex organic molecules through photosynthesis in plants and becomes part of
their molecular makeup.
Animals eating those plants in turn absorb Carbon-14 as well as the stable isotopes.
This process of ingesting C-14 continues as long as the plant or animal remains
alive.
The C-14 within an organism is continually decaying into stable carbon isotopes, but
since the organism is absorbing more C-14 during its life, the ratio of C-12 remains
about the same as the ratio in the atmosphere. When the organism dies, the ratio
of C-14 within its carcass begins to gradually decrease. The ratio of decrease is ½
the quantity at death every 5,730 years. That is the half life of C-14.
People of the Earth, 10th Ed., p. 11.
technique
techniques