If you can imagine the one family continuously occupying the same land for 40,000 years or more, using it not just to sustain life but as a place of reverence and worship, where every tree, rock and waterhole had significance, you will get some understanding of the importance of land to indigenous people.
A line is an involuntary combination of people who are simultaneously irritated with one another and focused on a single, common circle of interests and goals. This leads to a mixture of rivalry, hostility, and collective sentiment, a constant readiness to close ranks against a common enemy - anyone who breaks the rules.