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Ah summer…the perfect time for a delicious guacamole quesadilla or a tasty avocado salad. But have you ever looked inside an avocado? Beneath the delicious green flesh is an immense hard seed as big as a golf ball. Trees compete by spreading seeds efficiently. The Norway maple in my back yard produces thousands of helicopter seeds which fly off in every direction on their own rotors. The black cherry entices countless birds to eat its fruit, pit and all, and thereby spread its seeds afar on feathered wings. What purpose does the avocado’s giant seed serve?
Well, avocado trees as a species are ancient. They evolved together with giant mammals like glyptodons, gomphotheres, and giant sloths. These immense herbivores could eat avocados whole and not even notice the seeds. The animals would forage away from the original tree and, in the course of time, leave the seed in a totally different location along with a pile of fertilizer. Osage oranges are similarly symbiotic with the giant extinct grazers. In the absence of these creatures, wild avocados and Osage oranges are slowly losing ground to other trees–even if human kind has planted the avocado for food and the Osage orange for its springy wood (which is perfect for archery).
So what happened to all these wonderful beasties? Why is a nature documentary shot on the grasslands of Africa today so much more satisfying then one from the great Texas Llano? Alas, they went extinct 12000 to 14000 years ago—just about the same time humankind showed up. It turns out the first humans to get to the New World loved killing charismatic megafauna even more than Buffalo Bill did.