How did the Parni nomads become part of Parthian society?

The Parni were a nomadic or seminomadic tribe belonging to the Dahae confederacy, originally living in the steppe region east of the Caspian Sea. Following the death of Alexander the Great in 323 BCE, the Parni migrated southward into the region of Parthia.123

As they settled in this territory during the 3rd century BCE, the Parni underwent a process of cultural integration. They adopted the speech of the native Parthians and were gradually absorbed into the settled population. This integration facilitated their rise to political prominence; the ruling family of the Parni established the Arsacid dynasty, with Arsaces I traditionally recognized as the founder of the Parthian Empire.13