The history of Bulgaria includes the period starting from the first settlements in the territories of modern Bulgaria, to its formation as a nation-state and includes the history of the Bulgarian people and their origin. The first human remains discovered in what is now Bulgaria date back to 44,000 BC. Around 5000 BC a sophisticated civilization already existed which produced some of the earliest ceramics and jewelry in the world. After 3000 BC the Thracians appeared on the Balkan peninsula. In 500 BC about they formed the powerful kingdom of the Odrysians, which subsequently went into decline and fell under Persian, Macedonian, Celtic rule and was later absorbed by the Roman Empire. This group of ancient peoples was then assimilated by the Slavs, who settled permanently on the Balkan peninsula after 500 AD.