Fossils: Examining the Past

Fossils

• A fossil is a remnant of ancient life.

Fossils

Osteology

• Osteology is the scientific study of the skeleton.

What can a skeleton tell us about the human it belonged to?

• Age at death

• Sex

• Lifestyle

• Diet

• How they died

Ephiphsyis/Diaphysis

Skull

Pelvises: male and female

Skulls: Male and Female

Dating Fossils

• There are a number of techniques for determining how old fossils are…

Law of Superposition

• The use of the law of superposition: simply put, fossils found closer to the surface are younger than fossils found further beneath the ground.

Radiometric Dating

• Radiometric dating measures the rate of decay of certain radioactive substances in fossils (or the rocks they’re found in) to determine their age.

Half-Life

• Half-life: the time it takes for half of a given substance to decay.

• The time it takes for a substance to reduce by half is the same it takes to reduce to the next half (i.e. a quarter)

Radiocarbon Dating

• Radiocarbon dating measures the decay of unstable Carbon-14 into Carbon-12.

• Carbon-14 has a half-life of 5,730 years. This technique is excellent for fossils dating back to about 40,000 years.

Radiometric Dating

• Potassium/Argon dating (K/Ar dating) measures the decay of Potassium into Argon gas. Radioactive potassium has a half-life of 1.4 billion years.