I don't think that Earth had 300M people in 1 c.e.
Roman empire with client states probably had population 30M, maybe another 30M for China and 30M for Indian subcontinent. These would absolutely dwarf everything else. No room for 3x of that.
Roman empire with client states probably had population 30M, maybe another 30M for China and 30M for Indian subcontinent. These would absolutely dwarf everything else. No room for 3x of that.
Even then, this link only suggests 250M population by 1 CE and not 300M. Deflate that number by another 50M and it would begin becoming plausible.