Are all people with the same surname family?

Although people with the same surname often say that they were family 500 years ago, this is actually just a way of making friends, and there is not much basis to speak of. For example, Confucius, whose surname is Kong, now calls Confucius an ancestor; In fact, there was also a man named Kong before Confucius. Liu is mostly the ancestor of Liu Bang, and Liu Bang itself ranks third. Even if it is really Liu Bang's family, it may not be Liu Bang's descendants.

However, there is some truth in the saying that it was a family 500 years ago. Everyone with a surname should belong to the same ancestor at the earliest. In ancient times, the Yellow Emperor gave anyone a surname, and then his descendants were a blood family. Later, emperors in all previous dynasties gave their surnames to those who made meritorious deeds as rewards, so several big surnames were emperors' surnames for many years, such as Li, Wang, Zhang and Liu.

However, some people change their surnames to avoid sin. If there is blood relationship, many people with the same surname are not family. Moreover, in ancient and modern society, the surnames of boys who remarried with their mothers were all stepfathers. This phenomenon is also quite common. After several generations, later generations simply didn't know their ancestors' real surnames. Therefore, being a family 500 years ago was just a way of expressing friendship, which may not be accurate.

Of course, there is an Eve hypothesis in molecular biology: all modern people are descendants of a woman who lived in Africa 200,000 years ago, and all the ancient people outside this branch died out in evolution, which means that all mankind may be a family 200,000 years ago.