I found Harvey's comments challenging, so I did a search on how the banana came to the Western Hemisphere and found the following article from the International Banana Association:
International Banana Association
It appears that I was not entirely accurate. The first banana's route to the Americas from SE Asia was through Africa, Europe, the Caribbean, thence South America. So, it was not from the Philippines to America. My contention that the yellow banana was already in existence, though, is still correct. The banana was brought to the Caribbean in 1516. Years before that, the Portuguese brought the banana to the Canary Islands where they were cultivated.
It would be extremely unlikely that a
natural hybridizing process could occur in a short span of 20 years. Unless, one of the Jamaican farmer's workers performed a "grafting process" similar to Mauro's. And so, why not? If hybridizing can be done on a cellular level, the "splicing" of two different corm halves is just the same procedure. Only it is done with several thousand times bigger materials.