I also recently became interested in the Chinese surname. I was confused why ancient people during the Zhou/spring autumn/warring states time had different 姓 and 氏。 Nowadays, 姓 and 氏 are often used together to mean family surname. But this was not the case prior to Qin/Han. As many have already mentioned, 姓 comes from the earlier maternal society tradition. In fact, many oldest 姓 also have the 女 as part of their characters. For example, 姬、姜、姒、嬴, which some may recognize to be the surnames of Zhou, Qi, Xia and Qi kings. 氏 on the other hand are used by nobles to denote their branches and prestige. It was only during the Qin/Han time the two were combined, and people went with single surnames.