Theories are vital tools for developmental researchers because they ensure proper use of research procedures. illustrate the ultimate truth regarding human behavior. provide organizing frameworks for our observations of people. do not require scientific verification.

The answer is  provide organizing frameworks for our observations of people.
Theories became the very foundation of every studies because all studies are constructed in such a way in order to prove whether the theory is correct or false.
From this conclusion, the researchers could later on provide explanation on how the theory is proven to be correct or wrong and provide future researches with datas that they could use to develop the knowledge further.

Yes you are cute answer theories to explain the colonization of the new world the last great habitable landmass to be occupied by humans focus on the bering land bridge, or beringia, which emerge by siberia and alaska the last ice age.