Consider a planet where there is only one type of organism. And this organism reproduces through fission.
Thus the offspring is exactly similar to the parent. These organisms are multi-cellular and similar to human in structure and behavior but every single body is genetically identical to the others.
What may be the other ways which they may use to avoid confusion among them and to identify a specific individual?
The population in the planet is about 100 million units. And their technology is similar to our year 1900.