Migration
Migration started because of a few reasons. For instance, the weather got colder, their food moved, and they needed better shelter.
The way early man migrated was either going to Europe or Southwest Asia. As they kept migrating, they all ended up in South Asia. Still migrating we go three different places: East Asia, North Asia, and Australia. Then we all end up in North America to settle again. Lastly, we all finally settle in South America.