There was once a time when you could only get ethnic foods by going to that country or area of the world that it was found. Not only that, but there were regional foods within the greater ethnic area. The only people that ever got to experience these wildly different and exotic foods were the wealthy or royalty. The common folk never even knew about such things unless they heard rumors of it from the higher class. Because of this culinary isolationism, there wasn't even a thought of combining these different ways of cooking into any kind of fusion cuisine.
As the world evolved technologically, it began to be easier, not to mention profitable, to ship exotic spices around the globe. In fact, the early trading companies made fortunes by bringing crates of spices from point A to point B. Spices were the easiest to transport as opposed to some of the more perishable ingredients. I'm pretty sure that over time, recipes were brought back and with the spices, regional chefs could make something close to the original. However, they never saw the originals made and probably had some guesswork involved and even put their own spin on things. Thus fusion cuisine was unwittingly born. That term, though, wouldn't be used for hundreds of years.
As transportation methods got quicker and cheaper, goods, people, and ideas started to spread more rapidly. Where people went, their ethnic foods and cooking knowledge went with them. On top of that, with refrigeration and/or freezer technologies, those once super perishable ingredients could make the voyage, too. This is where all these ethnic foods started getting more accessible to common folk.
At that point, fusion cuisine, as I would imagine, ceased to be much of a thing. Everyone was excited about these "new to them" traditional dishes as they were made in their point of origin. Fast forward a few years and everyone is so used to being able to drive downtown and have their pick of many different traditional ethnic foods. Even grocery stores have exotic ingredients for the brave or adventurous home cook. After years of this, people start to get bored with "traditional" ethnic foods and begin looking for the next new thing. Seeing that there weren't other cultures to discover or a new exotic spice from the other side of the world to be shipped in, there wasn't an easy answer.
That is until brave and adventurous chefs started to again mix their foods with others to create something new. Many of these chefs even spent time traveling the globe to see how all these traditional ethnic foods were made before they stepped into the realm of fusion cuisine. With their newfound expertise on multiple cooking techniques, it was a relatively simple and natural act to start combining them. Some people may think that fusion cuisine is a fairly new thing, but it has actually been evolving for at the very least, hundreds of years.
Tim Hiller is a freelance writer that enjoys writing about food, but more so is delighted to eat food, particularly Latin fusion dining. http://www.osorioslatinfusion.com