Lamech chose to practice polygamy and thus he knowingly plunged deeper into rebellion against God. Fortunately, none of Lamech's sons are mentioned in order to attribute a great crime to their names (but neither are they mentioned for their righteousness). Rather, they are noted for their extraordinary contributions to human society.
Adah, Lamech's first wife (or at least the first in order), bore Jabal:
Adah gave birth to Jabal; he was the father of those who dwell in tents and have livestock. (Genesis 4:20)Earlier in Genesis 4, Scripture states that Abel was a keeper of flocks (Genesis 4:2). Men as early as Abel made a living by keeping certain animals. What then is Jabal famous for? Clearly, he is not merely the father of those who possess livestock.
Rather, Jabal was the father of all those who dwell in tents and have livestock. Jabal was the first to improve the skill by dwelling in a portable habitat. He became an expert in combining these two skills to make a living.
Jabal's lifestyle must have been highly appealing to others, thus some of the earliest humans must have mimicked this new mode of living. However, it would be unwise to assume that all of human society maintained this primitive lifestyle up until the flood. Some humans also lived in more permanent habitats (such as The City of Enoch).
As human technology continued to develop, the variety of jobs and skills continued to grow. Jabal's brother, Jubal, was another man who made key contributions to the advancement of human culture and technology— a contribution which is clearly seen even to this day.
The Father of Musical Instruments - Jubal - Genesis 4:21
The City of Enoch - Genesis 4:17-19
Cain and Abel: Two Routes - Genesis 4:1-2
What Does the Bible Say About Polygamy? (Part 1) - Genesis 4:19
Cain and Abel: Murder - Genesis 4:8