Chaos happens when changing politics, which is done at the chieftain hut/residence/town hall. It lasts for 24 hours, the building will show how long, until finished. This is a good time, to use a "h o r s h o e", which will boost food production. Also, you can send troops and animals to locations, that have a lot of food and let them eat there, instead, If food runs out, they return to the town they came from.
Changing politics for a 2nd, 3rd, 4th time, etc, has a bigger penalty, you will lose a level off every building, including resources spots, like food. Any level 1 promoted buildings will be completely lost. This can be a big problem, with housing.