There's tons of good reasons. One of them is Malaria, which makes immigration and population density literally fucking impossible until the 19th century. Another is geographic isolation of many populations, making even a common language impossible. Another is lack of navigable waterways. Another is the huge swathe of predatory animals.
If it's not on the Red or Mediterranean Sea, you're basically fucked.
There's tons of good reasons. One of them is Malaria, which makes immigration and population density literally fucking impossible until the 19th century. Another is geographic isolation of many populations, making even a common language impossible. Another is lack of navigable waterways. Another is the huge swathe of predatory animals.
If it's not on the Red or Mediterranean Sea, you're basically fucked.