Like the Bronze Age, the succeeding Iron Age – when iron became the principal material for making tools and weapons – began at different times in different regions. The earliest evidence of iron working comes from the Near East, and dates around 1200 BCE .
Iron working appears to have developed independently on the Indian subcontinent around the same time, and a little later in China. It spread into Europe from the Near East, probably via the Caucasus, and had spread across the entire continent by 500 BCE . Some places, such as sub-Saharan Africa, skipped the Bronze Age altogether, as iron directly replaced stone.
Before the Iron Age, the only iron in use was that found in meteors in its elemental form, but this was rare and used only for decorative objects such as beads. It was not until people learned to extract elemental iron from its mineral ore by smelting that a technological revolution became possible.
Wrought iron is generally softer than bronze, so iron tools wear out faster. But iron took over from bronze partly because sources of iron ore are much more widespread than sources of copper and tin, and partly because iron implements are cheaper to produce. Iron hoes and iron nails were important innovations in agriculture and construction respectively.
The technique of adding carbon to iron to make steel – which is harder and stronger – was certainly known by the time of the Romans. The proportion of carbon was critical: add too little, and the iron is not hard enough; too much, and it turns brittle. This made steel items more expensive, and wrought iron stayed in use for cheaper items.
The Bronze Age created societies with small elites because the technology that gave people power was so expensive. In the Iron Age, with iron tools and weapons more widely available, power was more evenly distributed, although there was still some social stratification. The difference can be seen in modes of warfare in ancient Greece. Homer’s Iliad describes the Trojan War (set during the Mycenaean Bronze Age) in terms of single combat between kings and princes, who ride into battle in chariots. But following the rise of the Greek city-states around 750 BCE , wars were fought by all adult male citizens, who had to supply their own arms and armour, and who fought as infantrymen in well organized formations.
The Celts
In several parts of the world – the Mediterranean, and across south-western, southern and eastern Asia – iron-working technology was developed by societies that were already partly urbanized. However, societies in temperate Europe during the Iron Age were still pre-urban and largely tribal. Many of these, especially in western Europe, have come to be known as ‘the Celts’. But although they had linguistic and cultural elements in common, they would not have identified themselves as Celts, and DNA analysis shows that there was great genetic diversity. These tribes were village-based peasant farmers. Villages may have had headmen, but kinship is likely to have played an important role in social organization. Iron tools enabled them to clear forest faster than before, and they also drained marshes. The numerous hill forts typical of the period indicate that war was not uncommon, but these forts were probably only occupied in times of danger. When the Romans invaded Gaul (France) and then Britain, the hill forts proved inadequate defences against the organized military might of an established urban civilization.