A Third Ghost

Steve and I both posted examples of two "ghosts of evolution" - plants that have evolved with animal "partners" to disperse their seeds, who have since gone extinct. These were the osage orange and the devils claw, both plants mentioned in Connie Barlow's book, Ghosts of Evolution. Earlier this week I thought that it would be great to do another post if I could find another example when I had one of those "Oh, duh" moments and realized that there were thousands of them around me. This is an avocado tree (Persea americana) located in a vacant lot around the corner from my house. You don't see any avocados in this picture as all of us that route our dog walks under this tree pick anything that is ripe within reach. You've got to go 8 or 9 feet up before you see any fruit. But there are many of these in this region as this picture proves.

Unlike the osage orange, the fruits fall around the tree but there are many animals and insects who will eat them. However, none of them is big enough to carry the large avocado seed away.

According to Barlow, there are no animals left in Central America where this plant evolved, who can swallow an avocado whole, digest it, and carry it away from the parent tree. It seems clear that an elephant-like animal, a mastodon or gomphothere, extinct for 12,000 years, was the intended consumer of avocados.

This tree is very fortunate in that its fruit is favored by humans, who have extended its range around the world.