Blend of culture through spices

Lately food has been my concern when I travel. I can help but think why the same, say, fish cooked differently in other part of the world. One thing for sure it's due to the availability of other ingredients needed. But from the ancient time spices has also been traveling with the country that produced it. So what happened, did those spices brought because the receiving country need it, or was it brought because the coming one need it to cook while they were in the country doing some trade. Recently I went to Lasem, a small city in central java where it is believed that every foreigner come to Java through this city. One night I eat what is called "Bistik Jawa" or Javanese Beef Steak, where it is actually a meatloaf server with boiled carrot and bean, chips and sauce. What interesting is in other part of Java there's a similar meal called "Selat Solo" which is actually the javanese beef steak, a heritage recipe from the Dutch colonial era. The different is in Lasem the sauce used is the Chinese sweet and sour sauce, while in other Javanese it is the sweet sauce made from soy bean. I suspect this recipe was originally from Java, the "Selat Solo" with the sweet soy bean sauce, which then modified when the chinese came to Lasem. Which can be true because in Lasem there are many "klenteng" or chinese house of prayer indicating there used to be, and still are, many chinese people lived here. Another example is the Lontong Tuyuhan, rice cake served with chicken curry. The chicken curry is light like traditional Javanese chicken curry, but the taste is richer like Indian chicken curry. So I also suspect there used to be Indian coming to Java through Lasem, though I did not find any Indian during my 2 days in Lasem. I believed we can see culture encounter through food. It can explain which country had relation back in the past. But above all, food is a festive, whether you are interested in the culture behind it or the taste an sich.