... 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

ArchaeologicalDatingMethods

In the Field and Lab techniques = specific tools / procedures used methods = basic overall approaches to a problem

In the Field and Lab archaeological dating methods 1.relative dating 2.chronometric dating (aka absolute dating)

Relative and Chronometric Dating Understanding Humans, 10th Ed., p. 189.

Understanding Humans, 10th Ed., p REM: relative methods tell you whether something is older / younger / the same age

methods Understanding Humans, 10t h Ed., p 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. methodtechnique

People of the Earth, 10t h Ed., p. 11. technique techniques

In 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 REM: relative methods tell you whether something is older / younger / the same age

Humankind Emerging, 7 th Ed., p. 24.

People of the Earth, p. 18.

Main gorge at Olduvai. Note geological beds. Understanding Humans, 10t h Ed., p. 197.

Hoebel, Anthropology: The Study of Man and Archaeology, 4 th Ed., p Olduvai Gorge, Kenya. Bed I

In the Field and Lab archaeological dating methods 1.relative dating 2.chronometric dating (aka absolute dating)

In 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 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 Lab A.1. or First Order Absolute Dating direct determination of age based on internal evidence e.g., 14 C dating of bone sample e.g., dendrochronology e.g., molecular clocks

Relative and Chronometric Dating Understanding Humans, 10 th Ed., p. 189.

Technician in a radiocarbon dating laboratory. Understanding Humans, 10t h Ed., p. 194.

Radiocarbon dating: method was developed in the 1940s 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 earths 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, 10t h Ed., p. 11. technique techniques