What happened in 400 bc for Celts?

Economics did not change much during this period. Iron -a functionally superior metal to copper- was now used to construct tools. Although agriculture was still very important, improved farming methods enabled parts of the population to pursue other means of making a living while relying on the availability of food produced by others. Some people for example specialised solely in the crafting of tools, while others devoted their life to religion. As the population continued to increase Europe became more crowded, so that it was no longer possible to find new fertile farmland simply by migrating.

Shifts took place in cultural and political life. From the large number of cultures that had come to exist during the first appearance of agriculture in Europe, a few had developed further and come to dominate. While the Greek culture for example developed in the south-eastern part of Europe, north-Western Europe and central Europe saw the appearance of relatively new cultures. The Celtic culture came to dominate large parts of Europe, while the Germanic culture was firmly established in northern and north-eastern Europe. Eastern Europe on the other hand was dominated by new cultures from Asia. The Germanic and Celtic cultures were each composed of many separate groups that had similar cultures, yet each group had its own territory and political organisation. The first signs of conflicts between "states" became manifest as each group held on to its own culture and territory.