Why are East Asian Countries so Ethnically Homogeneous?

East Asian countries are often very ethnically homogeneous because people have lived together for a long time and shared the same traditions.

Imagine you're playing with your best friend every day after school, and both of you like to build sandcastles in the same way. Over many years, more friends join you, all of them building sandcastles the same way too. Soon, everyone at the beach builds sandcastles just like you! That's kind of what happened in East Asia: people lived close together, shared language, customs, and even food for thousands of years.

Think of it as a big family that has been living next door to each other for generations. They all speak the same language, eat similar meals, and celebrate the same holidays, just like how your mom and dad might have the same traditions as your grandparents.

Even when people moved from one place to another, they often brought their culture with them, so everyone stayed connected. That’s why East Asian countries are still mostly made up of one main group of people today, it's like a big family that never really changed!