Noah's descendents traveled a great distance, both physically and spiritually, from the landing of the ark on the mountains of Ararat (present day Turkey) to the plains of Shinar in Babylonia (present day Iraq).  

Gen 11:1
Now the whole world had one language and a common speech.

Gen 11:4
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."

In Gen. 9:1 God tells Noah and his family to “fill the earth”. God didn’t say to go build cities for yourselves. Cities often require leaders who lead the people away from the authority of God.

The people wanted to “make a name for ourselves”. What “name”? And they didn't want to be scattered. Yet this is exactly what God wanted them to do. In fact, that is exactly what He DID do. Sounds as if pride was creeping in and we know what happens with pride.

Is there anything significant that the people built the Tower of Babel out of brick instead of stone? Stone is something found in nature, something created by God, each one unique. Brick is man-made and uniform in appearance. Seems as if the people wanted to do things on their own, and not do things God's way. Isn't that just like us? Do we often make our own plans and then ask God to bless them instead of asking God what His plans are for us?

Another interesting thing - the Hebrew word for mortar is the same root word used in the word for materialism. The ways of the world are what bound the people together in the days of the Tower of Babel. The people in those days rebelled against God. Anything changed today? The words of the prophets are very clear. In the last days there will be a great confederation of rebellion and worldwide religious apostasy. There will eventually be a one world political and religious system in place (the bricks in the Tower of Babel), all bound together with a common love of materialism (the mortar in the Tower).

Once the people were scattered and their language confused, they congregated in groups with common languages, creating ethnic clans.

A word of caution concerning the commentary on page 21.  Mention is made that the first child is born much earlier than before in the lives of the people.  However, we are not told in Scripture that the names listed in the genealogy are the first ones.  Names are listed if they are noteworthy in the genealogical record.  Not all names were listed.  In fact, most of the names were not listed.  Otherwise, the Bible would be full of names.

Also, concerning the book of Job...several historical records place Job between Genesis and Exodus - after the life of Joseph and before the life of Moses. 

People begin to live shorter lives after the flood. Why? The protection of the canopy was gone, and the people were subjected to solar and cosmic radiation of which they were not accustomed. Before the flood the canopy prevented radiation from striking harshly against the earth. The atmospheric gas was higher in oxygen than it is now and air pressure was approximately twice what it is now. After the flood when the canopy fell radiation damaged cell structure of the human body, oxygen ratio was lowered and pressure diminished.

The things that caused longer life is gone...all because of...sin!  Because of sin, God removed the protective canopy.