There are THREE main views:

1) They spoke Hebrew. Those who espouse this view believe this because the book of Genesis, which was written by Moses, was written in the Hebrew language. But it is possible that Moses wrote it in Hebrew because “he spoke the Hebrew language.” In other words, Moses simply gave the “Hebrew equivalent of the language they spoke.” There are English translations of the Bible that give it the “English equivalent” and this is true of every other language that the Bible has been translated in.

2) They spoke a special language referred to as the “Adamic language.” Those who believe this think that it was either “the language God used to communicate with Adam” or “the language that Adam invented with which he then named all things.” (He named the “animals” in Genesis 2:18-20. He called his wife “woman” in Genesis 2:23. And he later called his wife “Eve” in Genesis 3:20).

3) We simply don’t know and can’t know. Why? Because God NEVER TOLD US. It is best not to speculate WHEN GOD’S IS SILENT.

We do know that whatever language they (and their descendants) spoke was changed by God. Where do we learn this? In Genesis 11:1-9 which reads: “Now the whole earth had ONE LANGUAGE and ONE SPEECH. And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar, and they dwelt there. Then they said to one another, ‘Come, let us make bricks and bake them thoroughly.’ They had brick for stone, and they had asphalt for mortar. And they said, ‘Come, let us build ourselves a city, and a tower whose top is in the heavens; let us make a name for ourselves, lest we be scattered abroad over the face of the whole earth.’  But the LORD came down to see the city and the tower which the sons of men had built. And the LORD said, ‘Indeed the people are one and THEY ALL HAVE ONE LANGUAGE, and this is what they begin to do; now nothing that they propose to do will be withheld from them. Come, let Us go down and there CONFUSE THEIR LANGUAGE, THAT THEY MAY NOT UNDERSTAND ONE ANOTHER’S SPEECH.’ So, the LORD scattered them abroad from there over the face of all the earth, and they ceased building the city. Therefore, its name is called Babel, because there the LORD confused the language of all the earth; and from there the LORD scattered them abroad over the face of all the earth.” Today we still have many different languages around the world and this passage teaches us why. Men wanted to build this huge city with a high tower to “make a name for themselves.” It is obvious that “God was not in their thoughts” and thus they, in pride, wanted to “glorify MAN instead of God.” They reasoned that if they could bring about this GREAT UNITY they would be united forever. This was a definite act of rebellion, for God had told Noah and his sons, “Be fruitful and multiply, and FILL THE EARTH” (Genesis 9:1). So, God “confused their language” in order to break up their grand union and to fulfill His purpose for men to “fill the earth.”

The city and the Tower of Babel foreshadow a coming day when men will once again try to achieve a GREAT UNITY by building a religious, political and economic system in defiance of God. The city and Tower of Babel later became the ancient city of Babylon and in Revelation chapters 17-18 we read of “Babylon the Great, the Mother of Harlots” (Revelation 17:5). It will be both a Satanic system and a literal city.  Instead of a “tower reaching up to heaven” we read “her sins have reached to heaven” (Revelation 18:5). God will then destroy this wicked system and city and their hopes of unity will be dashed to the ground just like the city and Tower of Babel were when God confused their language.  (DO)  (496.1)