Events from 400 BC

La Tène culture spreads - Celtic art and culture across Europe, skilled metalwork

Crop rotation practiced in Greece - beans restore nitrogen, agricultural productivity increases

Panini composes Sanskrit grammar - most complete grammar of any language until modern times

Hippocratic Oath formalized - 'First do no harm,' medical ethics foundation for 2,400 years

Celtic iron mining expands - Noricum (Austria) becomes famous for high-quality steel, Celtic smiths supply Mediterranean

Celtic oppida urbanization begins - fortified towns with organized streets, markets, coin mints, populations reaching 10,000

Athenian wine laws - symposiarch controls mixing ratios (usually 3:1 water to wine), unmixed wine considered barbaric