Dating

1. Radioactive Half-Lifes2. Index Fossils3. Tree Rings4. Genetic

Earth’s Timeline

Life Form

Microbial (prokaryotic cells)3.8 Billion

Complex (eukaryotic cells)2 Billion

First multicellular animals1 Billion

Vertebrates (simple fishes)500,000,000

Amphibians350,000,000

Reptiles310,000,000

Mammals200,000,000

Nonhuman primates60,000,000

Earliest apes25,000,000

Bipedal Hominids6,000,000

Modern human Ancestors 200,000

Dates of Life

1- Carbon 14

Compares ratio of carbon 14 to carbon 12

Good for up to 60K years

Has a half-life of 5730 years & we can date 8-9 half-lifes where 1% of the original C-14 remains.

At any given moment all living plants and animals have approximately the same percentage of carbon-14 in their bodies. After death carbon-14 decays but carbon-12 does not – so the ratio changes

1- Half Life

1. Potassium-40 found in your body at all times; half-life = 1.3 billion years2. Uranium-235; half-life = 704 million years3. Uranium-238; half-life = 4.5 billion years4. Thorium-232; half-life = 14 billion years5. Rubidium-87; half-life = 49 billion years

Carbon-14 good for plant or animal life or things made from them but not sea life.

1- Carbon 14

A common fossil known to have lived in a particular geologic age for a relatively short period of time that can be used to date the rock layer in which it is found – Relative Dating

2 - Index Fossils

3 - Tree Ring Dating

Genetic Dating/Clocks

A technique in molecular evolution used to measure the time of divergence of two species from a related ancestor. The length of time is calculated by measuring the number of molecular differences measured between the species' DNA sequences.