These days, every new decade seems to bring a new technology that totally upends the way we live our lives, but the ability of new technologies to disrupt societal structures is not new. Many times in history, the development or introduction of a new technology had far-reaching effects on how people lived their lives. One such technology is iron. The development of iron for military purposes—to make stronger weapons and tougher armor—led to plenty of disruption, but iron could have powerful effects even when used for peaceful and mundane purposes.

One place we can see an example of iron’s effect on society is in southern Scandinavia. The Iron Age began in Denmark around 500 BCE. The changes that came as a result can be seen throughout much of northern Europe, but they have been particularly well studied in Denmark.

Southwestern Denmark is rich in deposits of bog iron, a form of iron ore that is comparatively easy to extract and process. Iron was soon put to use to produce stronger swords, axes, and spearheads, but it was also used to make sturdy blades for agricultural tools such as sickles, scythes, and pruning knives.

The introduction of iron-bladed tools made possible a dramatic change in the agrarian economy. Earlier flint or bronze tools could not hold a cutting edge well enough to effectively cut large quantities of hay or twigs to be stored as fodder for cattle. Accordingly, cattle could only be kept in relatively small numbers to avoid overgrazing the sparse vegetation available through the winter. With iron tools, winter fodder could be cut, dried, and stored in quantity for the winter, allowing large herds of cattle to be kept in denser concentrations. These cattle provided meat and milk as a food source in addition to the grain people were already growing.

Cattle also produce something else: manure. Manure is a rich source of nitrogen for fertilizing fields. With larger herds of cattle producing more manure, exhausted fields could be refertilized without a long period of lying fallow, which increased grain production.

Keeping larger herds of cattle significantly increased the available supply of food, which allowed for population growth. It also, however, changed social relations. Before iron, individual families largely tended their own fields and kept small herds of cattle, producing only enough for their own subsistence. There was little social differentiation between one family and the next because everyone did essentially the same work and there weren’t many opportunities to get richer than your neighbors. With iron came larger cattle herds, which meant that some people had to do the dirty scut work of cutting hay and mucking out stalls, while those who owned the cattle enjoyed extra food to use for trade or creating new social connections through the giving of expensive gifts. The archaeological evidence from Iron Age settlements in Denmark shows a process of social differentiation, as some families consolidated their economic power and rose to the top while others became dependent workers supporting the new elite.

The availability of economic surplus in the form of grain, cattle, and trade goods also meant that raiding nearby settlements could now be a profitable way of life for those strong enough to get away with it, and so the new cattle-owning elite soon also put iron to work to equip themselves for defense or to launch raids of their own. The agricultural elite became in time a military elite, with farming duties largely handed off to dependent workers. In time, this military elite consolidated its power enough to found royal dynasties commanding wide swaths of land and conducting raiding activities far from home.

These changes did not happen quickly. Unlike the effects of electricity, automobiles, and the Internet in the modern world, the effects of iron in ancient Denmark played out over centuries. The changes came slowly enough that, in lived experience, they probably did not seem all that disruptive. Looking back with the perspective of archaeology and history, though, we can see what enormous social transformations can be traced back to the introduction of stronger tools made of iron.

The most disruptive technologies don’t always come from the sources you expect, nor can we always predict the long-term effects of what seem like simple changes. These observations may seem very modern to us, but they were as true in the past as they are today.

Image: Raw bog iron, photograph by Tomasz Kruan via Wikimedia

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