Scientists believe that people long ago needed food, so
they followed herds of mammoths to North America.
People long ago used weapons because they needed to find
3. Because they wanted to
learn about life long ago,
archaeologists studied artifacts. ________________
learned to grow food, and as a result,
their lives became easier. _________________
5. The glaciers began to melt
and therefore the land bridge
between Asia and North America became flooded.