Vavilov concluded that the most likely areas of origin were where the plant was cultivated and the wild ancestors grew. Further, the areas of origin should be areas in which there was lots of variation. He decided that there were 8 major areas that met these requirements. Later, he added more till he got up to about 20 or so. Harlan concluded that it is very difficult to separate the origin and later expansion of a successful crop.
Every model generated so far has evidence for and against it.
Some were for ritual, magic, ceremony, or religious sacrifice. Some weeds gave rise to crops. Some crops gave rise to weeds. Some weed-crop complexes had common progenitors. Some crops arose in Vavilov's centers, some did not.