Who were the original avocado, ginkgo fruit, breadfruit, osage orange, mango, grapefruit, and pomegranate eaters? It was not people, right? Apparently, the original eaters were Cenozoic megafauna. See more on http://darwiniana.org/ghostsof.htm
is easily the oddest:...animals such as cats, dogs, cattle, goats, rabbits, birds, and fish can be severely harmed or even killed when they consume the avocado leaves, skin, or pit. The avocado fruit is poisonous to birds. Avocado leaves contain a toxic fatty acid derivative known as persin. Birds seem to be particularly sensitive to this toxic compound...The avocado was adapted for ecological relationship with now-extinct megafauna (such as the giant ground sloth). The fruit, with its mildly toxic pit, co-evolved with megafauna mammals to be swallowed whole and excreted in their dung, ready to sprout. The avocado's ecological partners have disappeared, and the avocado plant has not had time to evolve an alternative seed dispersal technique, aside from human cultivation.
Perhaps 10,000 years from now there will be endless speculations what kind of a large animal swallowed whole avocados and excreted pits in year 2007 AD...