CHAPTER THREE THE EARTH AS HUMANITY’S HOMEFrom the moon, the astronauts saw the Earth at a single instant in its nearly 5-billion-year history. What the astronauts could not see was the changeable nature of Earth’senvironment.
But astronauts orbiting the Earth in the space shuttle can see a magnificent light show,courtesy of human urbanization.
If astronauts had orbited the planet 200 million years ago, they would haveseen one super continent (Pangaea).
Internal forces likely caused its breaking up. The continents continue to drift.
If astronauts had stood on the moon 20,000 years ago, they would have seen larger icecaps, huge ice sheets in North America and Eurasia, lower sea levels, and very differentcontinental outlines.
For more than a century the Land Bridge Theory went largely unchallenged. But recently,new evidence discovered has begun to challenge the long-prevailing theory. So once againscientists are once again asking the questions, “who were the first Americans,? And,“where did they come from?”
All agree that the physical characteristics of the planet more than 12,000 years agoplayed a vital role in early human migration to America. What ancient artifact is at thecenter of the current study? And how do the new findings challenge the long-existingtheory of early migration to America?Dateline 1933-Clovis, NM: The oldest spear point found to date (13,500 yrs old) is found. Scientistsbelieve it originated from Asian migration.At that time, the dating of the “clovis” spear point matches well with the geographical timeline of theLand Bridge.
Explain Pittsburgh’s role in the study. What is one alternative theory of early migrationto America (glaciation as a factor)? Cite the evidence discovered.At Meadowcroft, scientists found artifacts from earliernative inhabitants pre-dating 13,500 yrs & clovis (16,000yrs old).This finding casts doubt on the Land Bridge Theory and itis controversial.Ice sheets would have blocked human migration until atleast 13,500 yrs ago.
Researchers have discovered significantly greater numbers of clovis sites in the eastern U.S. than inthe Rocky Mountain region. What implications does this have in theorizing the direction from which theearliest Americans arrived?DNA v. Archaeology: DNA analysis indicates the first humans date back more than 20,000 years. Theanalysis also indicates 3 waves of migration. How does this impact the Land Bridge Theory?Weapons & tools in found in Asia were very different from clovis points found in North America.
Ultimately, physical geographic conditions on the planet during the last Ice Age may settle the disputeof competing theories. How might the Ice Age had made it possible for humans from modern-dayFrance (the Salutrians) to migrate to North America? If this theory is correct, where would thesepeople have initially landed?
To prove the “European Connection,” scientists would have to answer the questions of howearly humans migrated to America and when they migrated. Where did scientists ventureto simulate conditions of the Atlantic Ocean during the Ice Age? Did they prove theirtheory?
An obstacle for researchers is explaining a nearly 2,000 year gap between 13,000 years ago, the timeframe dating many of the clovis sites in the eastern U.S. and 11,000 years ago, representing anotherclustering of clovis-type sites. What drastic physical change is believed to have created this gap?
Drastic climate change in the form of a mini-Ice Age has become the prevailing theory to account forthe 2,000 year gap that breaks the archaeological timeline. Now, the controversy surrounds the causefor the climate change that apparently altered the planet. Identify the two prevailing theories andexplain how, ultimately, they have worked in tandem to create the catastrophic climate change.
This last clip theorizes the merging of the two origin theories (Land Bridge v. Europe). Explain thetheory of merging. Which animal becomes the primary food source? And, how does weapon adaptationadd support to this theory?
Has DNA data proven one theory versus another? The Clovis Point remains the key. Howmight the Clovis originated? Since this new study, what new components of early Americanculture develop? After watching the clips, what is your opinion?
The Late Cenozoic Ice Age began during the late Tertiary period and extended into thePleistocene epoch. There were as many as 30 glacial periods within a cycle of glaciationand interglaciation.
TIME AND SPACE The last billion years of Earth’s history is divided into 3 geologic eras. The K/T Boundary represents a sharp transition, making the extinction of many animals and plants. Geologic eras are divided into periods. These periods are divided into epochs.
One of the species to suffer extinction was dinosaurs. Explain the prevalent theory as tohow this species became extinct.
Scientists have been historically divided over whether the great changes on Earth’ssurface are exclusively the result of internal forces (volcanoes and earthquakes), or, theresult of a combination of internal forces and external forces (meteor strikes). Explainwhy, until recently, the inability of scientists to find whole meteor remains to supporttheir external forces theory.
Where do some scientists believe the meteor that destroyed the dinosaurs hit Earth’ssurface? Do all scientists agree with this theory? Why?
Some scientists claim that it is not a matter of “if,” but a matter of “when” an asteroidor comet causes a meteor strike on Earth. Explain how studying Jupiter provided someinsights on what could happen on Earth.
With the potential that an NEO (near Earth object) could strike Earth, identify some ofthe options being considered to protect our planet.
The Holocene epoch has only lasted 10,000 years, but the impact on human history hasbeen dramatic. The Earth changed as never before. Despite a relatively environmentallystable 10,000 years, the Earth continues to change. Internal forces creating earthquakesand volcanic eruptions continually change the planet’s surface. Above ground, erosion andweathering shape the surface.