national personification of the Swiss confederacy in the 17th century in a 1672 play by Johann Caspar Weissenbach. History The state of Switzerland took its present form with the adoption of the Swiss Federal Constitution in 1848. Switzerland's precursors established a defensive alliance in 1291, forming a loose confederation that persisted for centuries. Beginnings The oldest traces of hominid existence in Switzerland date to about 150,000 years ago. The oldest known farming settlements in Switzerland, which were found at Gächlingen, date to around 5300 BC. The earliest known tribes formed the Hallstatt and La Tène cultures, named after the archaeological site of La Tène on the north side of Lake Neuchâtel. La Tène culture developed and flourished during the late Iron Age from around 450 BC, possibly influenced by Greek and Etruscan civilisations. One of the most important tribal groups was the Helvetii. Steadily harassed by Germanic tribes, in 58 BC, the Helvetii decided to abandon the Swiss Plateau and migrate to western Gallia. Julius Caesar's armies pursued and defeated them at the Battle of Bibracte, in today's eastern France, forcing the tribe to move back to its homeland. In 15 BC, Tiberius (later the second Roman emperor) and his brother Drusus conquered the Alps, integrating them into the Roman Empire. The area occupied by the Helvetii first became part of Rome's Gallia Belgica province and then of its Germania Superior province. The eastern portion of modern Switzerland was integrated into the Roman province of Raetia. Sometime around the start of the Common Era, the Romans maintained a large camp called Vindonissa, now a ruin at the confluence of the Aare and Reuss rivers, near the town of Windisch. The first and second century AD was an age of prosperity on the Swiss Plateau. Towns such as Aventicum, Iulia Equestris and Augusta Raurica, reached a remarkable size, while hundreds of agricultural estates (Villae rusticae) were established in the countryside. Around 260 AD, the fall of the Agri Decumates territory north of the Rhine transformed today's Switzerland into a frontier land of the Empire. Repeated raids by the Alamanni tribes provoked the ruin of the Roman towns and economy, forcing the population to shelter near Roman fortresses, like the Castrum Rauracense near Augusta Raurica. The Empire built another line of defence at the north border (the so-called Donau-Iller-Rhine-Limes). At the end of the fourth century, the increased Germanic pressure forced the