The document discusses the theory that the first Americans migrated to North and South America across a land bridge between Siberia and Alaska during the last Ice Age. While this "Land-Bridge Theory" was widely accepted, newer evidence has challenged this view. Archaeological sites in South America and the Pacific Northwest have been dated to over 14,500 years old, earlier than presumed migration occurred. Additionally, some skeletal and artifact findings suggest the possibility of ancient migrations by boat from Europe or across the Pacific. Overall, the evidence continues to accumulate and revise scientific understanding of how and when the first people settled in the Americas.

1. The First Americans

2. Just a “Theory.”

A “theory” is a model based on, and
accounting for, all available evidence which is
intended to explain something.

We call something a “theory” not because it is
someone's “opinion,” but because we
recognize that at any given moment, new
information can completely revolutionize our
understanding and radically change our
explanations.

3. Example: Geocentrism vs.
Heliocentrism

For thousands of years, people believed that
the sun and other things in the sky (stars,
planets, etc.) revolved around the earth
because they appeared to.

Nicolaus Copernicus proposed that the earth
orbited the sun and this was later confirmed by
the work of Johannes Kepler (even though
Kepler started out to disprove Copernicus!).

4. The “Land-Bridge” Theory
For many years, the main theory about how
people first came to North and South
America was the “Land-Bridge” Theory.
This theory was that people migrated
across the Bering Strait when it was
exposed land during the last Ice Age
(12,000-20,000 years ago) and their
descendants populated North and South
America.

5. Evidence to support the “Land-
Bridge” Theory

Archeological evidence found in Alaska
matches the evidence found at Clovis, NM in
the 1920s. Evidence at Clovis is 13,500 years
old.

Mitochondrial DNA shows that Native
Americans have East Asian ancestors.

6. But....

In 1997, evidence at Monte Verde, Chile
turned up that was 14,500 years old.

A small amount of evidence suggests that a
European group called the “Solutreans”
migrated to America by boat.

“Kennewick Man,” a 9,500 year-old skeleton
found in Washington bears a strong
resemblance to the Japanese “Ainu” people,
suggesting a Pacific boat migration.

7. Adding to the mystery...

The Topper Site in South Carolina is estimated
to be 15,000 years old.

The Paisley Cave site in Oregon is estiated at
14,500 years old.

Skulls, charcoal and stone tools found in Brazil
have been claimed to be 50,000 years old and
are similar to Australian aborigines, Pacific
Islanders or sub-Saharan Africans.

8. Furthermore...

Most Native American creation stories do not
tell of a great exodus or migration, but that the
people were a product of the earth and sky
and have “always been here.”

For comparison's sake, the Bible is chock full
of migration stories (Adam and Eve cast out of
Eden, Abraham's journey from Ur, the exodus
out of Egypt, etc.)

9. Skull found in Brazil that could be of
Australian, Pacific Islander or Sub-Saharan
African origin.
Navajo creation story

10. Spear points from Clovis
Dwelling at Monte Verde
Projectile points from the
Paisley Caves
Studying artifacts at the Topper
Site