An interesting post at American Forests muses about the "hedge apple"/"Osage orange"/"monkeyball" (Maclura pomifera):
Consider the fruit of the Osage-orange, named after the Osage Indians
associated with its range. In the fall, Osage-orange trees hang heavy
with bright green, bumpy spheres the size of softballs, full of seeds
and an unpalatable milky latex. They soon fall to the ground, where they
rot, unused, unless a child decides to test their ballistic properties.
Trees that make such fleshy fruits do so to entice animals to eat
them, along with the seeds they contain. The seeds pass through the
animal and are deposited, with natural fertilizer, away from the shade
and roots of the parent tree where they are more likely to germinate.
But no native animal eats Osage-orange fruits. So, what are they for?
The same question could be asked of the large seed pods of the
honeylocust and the Kentucky coffeetree...
In terms of evolutionary time, the difference between 13,000 years ago
and now is like the difference between Friday, December 31, 1999 and
Saturday, January 1, 2000. We may assign those two days to different
centuries or millennia, but they are still part of the same week.
Likewise, all the animals and plants of 13,000 years ago belong just as
much in the present. In fact, they still live in the present, with just
one major exception: most of the big and fierce animals are now gone...
Now let’s return to the forlorn fruit of the Osage orange. Nothing today
eats it. Once it drops from the tree, all of them on a given tree
practically in unison, the only way it moves is to roll downhill or
float in flood waters. Why would you evolve such an over-engineered,
energetically expensive fruit if gravity and water are your only
dispersers, and you like to grow on higher ground? You wouldn’t. Unless
you expected it to be eaten by mammoths or ground-sloths...
It’s true that such adaptations are now anachronistic; they have lost
their relevance. But the trees have been slow to catch on; a natural
consequence of the pace of evolution. For a tree that lives, say, 250
years, 13,000 years represents only 52 generations. In an evolutionary
sense, the trees don’t yet realize that the megafauna are gone.
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