The Jomon are Japanese dated back before 300 BC to explain why they are supposedly brought about complexity to culture. They don't care aboutwhat happened before Jomons or their descendants but only about what features they inherited from them. And yeah we can promise you that there are Japanese people who believe this. Even outside circles the Jomon vs Yayoi thing is often featured in online articles comparing "Jomon faces" and "Yayoi faces". It's not obvious why Jomon people garner so much interest by modern Japanese.