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Scientists that study fossils and other clues that may help them reconstruct what past life was like

Relative Dating

The process of determining whether an event or object, such as a fossil, is older or younger than other events or fossils

Absolute Dating

Determining the age of an object or event in years, usually by measuring the amount of unstable atoms in a sample to decay


The time it takes for half of the unstable atoms in a sample to decay

Geologic Time Scale

The division of the earth's history into distinct intervals of time


Describes a species of organism that has died out completely


Means "All Earth" and is what the giant landmass was called

Plate Tectonics

It's believed that the earth crust is divided into pieces called tectonic plates. The continents ride on top of these plates, moving due to their motion

Precambrian Era

The time period from 4.6 to about 540 million years ago. During this time scients believe that life arose and changed the planet


3 billion years ago these were the first simple prokaryotes that were photosynthetic

Paleozoic Era

Time period from 540 to 248 million years ago. Means ancient life

Mesozoic Era

Time period from about 248 million to 65 million years ago. Means " Middle Life". Referred to as the "age of reptiles".

Cenozoic Era

From 65 million years ago and continues today. Means "recent life"


A group of mammals that includes humans, apes, monkeys, and prosimians. Have opposable thumbs and binocular vision.


The family referring specifically to humans and several extinct human-like species, some of which were human ancestors


Walking upright on two legs


Means "southern man ape". Had long arms, short legs, and small brains. Ex: Lucy

Homo Habilis

Lived from approximately 2.3 to 2 million years ago. Was a tool maker

Homo Erectus

Lived from 2 million to about 200,000 years ago. Spread out along the world, may have lived in caves, built fires, and wore clothing. It is thought that they were successful hunters who could kill and butcher large animals. Were larger brained than Homo Habilis


Early humans that lived in Europe and western Asia from 230,000 to 30,000 years ago. They were good hunters, made fires, wore clothing, cared for the sick and elderly, buried their dead


Lived from 100,000 years ago to near recent day. Are similar to humans today but had larger bones. They were good artists as shown by their cave drawings and sculptures

Homo Sapiens

Today's human species

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