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When do humans first appear on the clock?

The Earth is approximately 4.6 billion years old . Imagine 4.6 billion years condensed into one 24 hour day. The Earth begins to form here. When do humans first appear on the clock? What is happening between the formation of the earth and human existence?.

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When do humans first appear on the clock?

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  1. The Earth is approximately 4.6 billion years old. Imagine 4.6 billion years condensed into one 24 hour day. The Earth begins to form here When do humans first appear on the clock? What is happening between the formation of the earth and human existence?

  2. What does this tell us about the age of the earth compared to how long humans have lived on earth? http://www.businessinsider.com/animated-timeline-earth-history-2015-11 http://www.businessinsider.com/animated-timeline-earth-history-2015-11

  3. When homo sapiens (or hominids-”creatures who walk upright” ) finally begin roaming the earth around 200,000 year ago, they were very different from us.

  4. There was no writing... • Man only learned to write 5,000 years ago (around 3,000 b.c.e) • Humans, and their ancestors, lived for hundreds of thousands of years before anything was written down • If the first homo sapiens appeared around 200,000 years ago, that means homo sapiens had to communicate without writing for about 190,000 years.

  5. If early homo sapiens did not write things down... • What problems might have arisen? • How do we know about them?

  6. Archaeologists... • Study the culture and societies of people who are no longer alive • Study the artifacts they've left behind, since they can't observe their subjects or interview them. In the case of prehistoric people, artifacts (tools etc.) are especially important because they don’t have stuff for us to read. • Infer [conclude from evidence (artifacts)and reasoning rather than from explicit statements] what life must have been like.

  7. Carbon Dating • How do archaeologists know how old the artifacts they dig up are? • Radio Carbon Dating is a scientific process scientists use to figure out how old organic material is. • Everything that's alive absorbs a type of radiation from the Sun in the form of an isotope called Carbon 14. • When something dies, the Carbon 14 begins to break down • We know it takes 5,000 years for Carbon 14 to breakdown, so by measuring how much Carbon 14 is left in an artifact, we can figure out how old it is.

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