Until the episode at the tower of Babel (recorded in Genesis 11), everyone spoke in one language. But by creating that tower, man demonstrated his fallen nature --the desire was to make himself important; --elevating himself; --attempting to become like God. It was there that God took away his influential power by confusing the language which caused divisions between the people.
Then they said, "Come, let us build ourselves a city, with a tower that reaches to the heavens, so that we may make a name for ourselves and not be scattered over the face of the whole earth." But the LORD came down to see the city and the tower that the men were building. The LORD said, "If as one people speaking the same language they have begun to do this, then nothing they plan to do will be impossible for them. Come, let us go down and confuse their language so they will not understand each other." So the LORD scattered them from there over all the earth, and they stopped building the city. That is why it was called Babel-- because there the LORD confused the language of the whole world. From there the LORD scattered them over the face of the whole earth. (Genesis 11:4-9)
From that time on, nations have been unable to effectively communicate with each other because of the difference in their languages. However, at Pentecost God broke through the language barrier supernaturally by using the apostles and others to speak in foreign languages they didn't know.