Methods of Studying the Human Past
Chapter 9
Remains
•Sites:
•Fossils: preserved remains of plants and animals that lived in the past.
•
•trace
fossils: evidence of animals such as tracks or feces.
How are Sites or Fossils Created?
•Remnants of human activity or fossils are covered or buried.
•Volcanic activity
•Sediment deposition: edge of rivers, lakes, swamps
•Accumulation of duff
•
•Taphonomy: the study of what happens to fossils or sites from the time of death or
abandonment to the time of discovery.
•Why is this important?
How are Sites and Fossils Found?
•By accident: digging or erosion.
•Pedestrian Survey:
How are human fossils recovered from a site?
•Excavation: recovering fossils and other associated material (plant or animal fossils)
from the site.
•Provenience:
Analysis
•Reconstructing the Fossil
•
•Context: The relationship between fossils and associated remains.
•gives meaning to the site.
•
Dating Techniques
•Relative Dating:
•Absolute Dating: the actual age is determined on an absolute time scale (usually years
before the present or B.P.).
Relative Dating
•Stratigraphy:
•strata: layers of rock.
•Four principles used to relatively date strata and fossils contained within them.
•Principle of original horizontality: strata are laid down horizontal to the earth’s
surface.
•Principle of superposition: layers or deposits are laid down in successive layers.
•
•Principle of cross-cutting relationships: strata must exist before something can crosscut through it.
•Principle of faunal succession:
Absolute Dating
•Radiometric
•based on known rates of decay of radioactive isotopes
•Half-life:
Radiocarbon Dating
•14C breaks down to 14N
•half-life 5730 years
•
•measuring the ratio of C-14 to N-14, can estimate how long the organism has been dead.
•
Potassium Argon (K-Ar) Dating
•Measures the decay of potassium to argon.
•half-life 1.33 billion years
•
•Best used to date volcanic material rich in potassium.
Electron Trap Techniques
•
•The number of trapped electrons is proportional to the amount of time that the material
has been exposed to the natural radiation= age.
•approximately 50,000-150,000 BP
Uraniam Series (U-series) techniques
•measures the decay of uranium and thorium to lead isotopes.
•
•5000-500,000 BP