As I said, any various tribes before would have been flood victims, and 3100 BC is 200 years after the Septuagint's Flood date.
Think about what you're saying.
Noah's Flood happens, and in 200 years, Egypt has developed in a full kingdom, developed a language, culture, religion all its own, has millions of citizens, and all from, what, eight people? And that's just Egypt, that's not including all the other civilizations that were around at the time - while estimates vary, even the most conservative ones have well over 10 million people living on the Earth around this time.
10 million people from a group of 8 survivors in 200 years?
But putting that aside, we know that the victims you're talking about didn’t die in the flood. They’re culture and language show the development into what would become Egyptian civilization. What you’re suggesting, whether you realize it or not, is that there was a thriving, growing civilization of people, who all the sudden died out, and then, soon after that, a new, completely different group of people settled in the same area, adopted the dead civilization's language and culture, then went about so seamlessly that no one studying them years later would be able to figure out they were unrelated to the groups living there before them.
Oh, and you have the same problem for the Chinese. And let’s not even get into the fact that there were people living in Australia and the Americas at this point