Complex sentence: At the time of his birth native Latvians and serfs were a stagnant social caste with little opportunity for social movement, the Ruling of Riga's Senate opened new opportunities for future generations of inhabitants of Riga.
Split into simpler sentences: At the time of his birth native Latvians and serfs were a stagnant social caste with little opportunity for social movement. After the Ruling of Riga's Senate opening new opportunities for future generations of inhabitants of Riga.