Scientists and archaeologists still harbor serious doubts about who the people were that mixed with the Thracians around 5,000 years ago, from which Thracian civilization itself would emerge. But it is known that there were some who came from the North to the Balkans with their livestock, finding a place with a bright and attractive culture. It was the intermingling between the local population and the new arrivals that allows us to talk today of the Thracians.
The Thracians are well-known for their exuberant fighting spirit; but the history of a population is not built only on its wars and the exploits of its soldiers and leaders, as it is usually read in encyclopaedias and history books. Spread across Southeast Europe were groups of men and women who were highly skilled in working with refined metals, who were followers of a delicate mystique that worshiped the mother goddess, and who had complex funerary rituals immersed in symbolism.
There are many puzzles that arise when we investigate the ancient Thracians. For example, they had a rare ability for discovering and extracting natural deposits without harming nature. Archaeologists and anthropologists continue to be surprised by the kinds of advanced technological practices that the Thracians were using. If, as some scholars believe, they were intermingling with the people who inhabited Bulgarian lands since ancient times, they presumably exchanged knowledge, and their wisdom swelled as they incorporated the skills, practices, and information of the other culture.
Source : ancient-origins.net