Why are we given details about what the descendants of Cain did? Is there special significance to these details? Genesis 4 discusses the descendants of Cain:


  "Cain knew his wife, and she conceived and bore Enoch. When he built a city, he called the name of the city after the name of his son, Enoch. To Enoch was born Irad, and Irad fathered Mehujael, and Mehujael fathered Methushael, and Methushael fathered Lamech. And Lamech took two wives. The name of the one was Adah, and the name of the other Zillah. Adah bore Jabal; he was the father of those who dwell in tents and have livestock. His brother's name was Jubal; he was the father of all those who play the lyre and pipe. Zillah also bore Tubal-cain; he was the forger of all instruments of bronze and iron. The sister of Tubal-cain was Naamah." Genesis 4:17-22


Why are we given details about what the descendants of Cain did? Is there some special significance to these details?
To me, it sounds like a recounting of early civilization: domestication of animals, music, metallurgy, city building. A secular anthropologist would tell a story of hominids evolving over millions of years culminating with emergence of homo sapiens in Africa. Then the story shifts into high gear as humans migrated all over the world and culture, technology and cities grew. 

The first 11 chapters of the bible explain how we came to be and why we are the way we are. There are lots of similarities between the story the bible tells and what anthropologists think happened.