[dotnet00]

Prior to becoming hereditary, the caste system was employment based, so yes, in a sense every society has had some sort of caste system as someone responsible for say, cleaning shoes, was probably looked down upon in most societies compared to say, a king.

However, the key point of difference is that it was more deeply ingrained in Indian society and was made into a rather rigid hereditary system. While in other places the child of a shoe cleaner might end up marrying a trader or might end up working as a trader himself, doing so would have faced more resistance from society in India. This can still occasionally be seen in villages and sometimes even towns and cities, where individuals from different castes want to get married but are murdered instead, either by the community or even their own families.

This effectively forced those in 'lower' jobs like cleaning drains into that position for generations, inflicting a lot more unjust suffering upon them.