I read this once, remembered it, then came across it again. I'm writing it here for reference:
9. The avocado is a ghost of evolution. It was originally consumed by large creatures in the Pleistocene period (when modern humans appeared). Creatures the size of wooly mammoths would have eaten the avocado whole, and excreted its seed in their dung. As these giant creatures died off, man cultivated the avocados for his own use and it is this cultivation which meant the avocado survived extinction.