The earth’s history

THE EARTH’S HISTORYReview

Geologic time scale = record of earth’s history

Earth was created 4.6 Billion years ago. Its core was hot because as radioactive

material decayed over time, it generated heat.

4 billion years ago oceans formed as the planet cooled and water vapor condensed

3.3 billion years ago primitive algae formed

1.2 billion years ago multicellular organisms evolved

The earth 240 million yrs ago during Pangaea (when the land was all stuck together in one

mass)

200 million years ago the first mammals evolved

3 million years ago the first humanoids evolved

200,000 years ago both Neanderthals and Homo Sapiens evolved side-by-

side – Neanderthals went extinct Neanderthal vs. Homo Sapiens Scull

MOST of human history we were hunter gatherers

People who obtain food from what is available in nature by collecting plants, hunting animals, or scavenging animals.

This tends towards a nomadic or ever-moving life style

Early humans could have altered their environment by over hunting a species in one region to extinction – they think this happened to the giant sloth, saber-tooth tiger, and mastodons to name a few

Agricultural revolution 10,000 years ago

Led to: Population growth – more food supports more

people waste Buildings or primitive urbanization Slash and burn – changes natural ecosystem Habitat reduction ecosystem changes

reduction in natural resources Increase in number of domesticated animals Farmland Change in soil quality / loss of

fertility Flooding

Industrial revolution ~ 300 years ago

A shift from energy sources and society powered by humans or animals to fossil fuels such as coal or oil.

Improvements in quality of human life Consequences: Environmental and Social

pollution / climate change – reverse in the quality of life?

resource depletion social inequalities? loss of biodiversity resource depletion