Natural History

The osage orange is a tree with a shrubby growth habit and tough, burnished leaves. It's not prone to insect depredation because the leaves and stems contain latex, a sticky and distasteful sap that makes it difficult to eat. This latex is also present in the knobbly green fruit it produces.

The fruit is actually composite, made up of a million small flowers gone to seed and grown together. It's the size of a large softball and heavy. It is inedible to humans, and sometimes eaten by squirrels or other animals, but only rarely. The skin is very tough, and it's too big for even deer to eat easily.

This is curious, since fruit is meant to spread seeds, to increase a plant's range, and the osage orange fruit is rarely consumed by animals, especially not in any great quantity. Since it's never eaten, consumption won't spread its seeds, the way other fruiting plants spread. In Indiana it's considered an invasive pest, but not because of how it travels without human involvement: instead, the issue lies with how humans plant it. The plant exerts great energy every year to produce the essentially useless fruit, which will fall near the base of the tree or maybe roll down a nearby hill, pulled by gravity. Nothing more.

There's a certain understanding that nature produces no dead ends, because natural selection and the process of evolution ensure that only the most fit pass on their genes. Part of the problem is that evolution is not driven solely by natural selection. Partially, also, there is a misunderstanding of the word "fit": it can be solely related to terms of survival, how long an organism lives, or it can be more indirect--for example, how effectively an organism reproduces, so that even a tree or a fish that dies earlier on in its life can pass on its genes to future generations. There's also sexual pressures; for example, there's a species of bird where the male's tail grows to such ridiculous lengths during the breeding season that it can no longer fly. The male with the longest tail (assuming he can survive the treacherous period where he's at much greater risk for predation) will attract the most females, and have the most offspring. It's a huge waste of energy and a danger to all the male birds, but it's been effectively selected for by countless generations, because it's pretty.

But still, there's no obvious, modern explanation for the osage orange's fruits. It wastes nutrients and other resources on what's essentially a useless gesture towards reproduction, in a way that won't increase its range, spread its seed. The answer, instead, lies in the past.

Ten to twelve thousand years ago, during the Wisconsin era of the Pleistocene epoch, before the end of the Ice Age and the introduction of humans to North America (these two events combining to reshape North American fauna drastically), Indiana was populated with creatures like the mastodon, the dire wolf and the ancient bison. There were species related to ones we know today, but exaggeratedly larger: the giant beaver and the stag-moose, and the teratorn, a bird with a twenty-six foot wingspan. It was also an unfamiliar landscape, with glaciers retreating and then advancing in cycles, flattening the land, but most strikingly different were the animals, who seem almost unbelievably ridiculous, almost fake, today. For example, there was the giant sloth.

The giant sloth stood at a comparable height with a mammoth, although it was less massive. It was an herbivore, but armed with heavy claws, and many times the size of the modern sloths. With the introduction of humans to North America, as they crossed the Bering Land Bridge, it was hunted into extinction, along with all its relatives. Some of them--the antique bison, the stag-moose, the sabre-toothed tiger--developed into smaller species; others were simply lost. Among them the giant sloth.

The osage orange had evolved to have its seeds spread by the giant sloth. It was a big enough animal to eat the fruits, as hard and solid and heavy as they were, in one bite; and it traveled, spreading the seeds away from the plant as it went. An animal that big ate a lot of vegetation, and it enabled the osage orange to spread across a considerable stretch of North America, perfectly adapted to coattail onto this animal's travels.

But change happened. Giant sloths were wiped out, unable to stand up to the introduction of a new biological factor--humans. Not fit to deal with this new type of predator, the megafauna were lost. The environment shifted, climate change happened, and the osage orange did not find a new niche to inhabit. Its territory slowly retreated, until it was limited to only the Ozark mountains, a relic of a long-gone epoch remembered only in fossilized skeletons, tar pits and ice-mummified mammoths.

Currently, osage orange is found throughout the East coast and the Midwest. It was re-introduced by humans: it is unable to spread quickly or efficiently without an herbivore big enough to consume its fruit. Instead, its fast-growing habit and the way it forms thorns on bruised branches made it a desirable hedge-plant for fencing in fields and properties. It was one of many opportunist species, and it persists, once more spreading across the country. But it is reliant on this conscious aid.

The osage orange may evolve another reproductive trait. Maybe the seeds will shrink back down to something smaller, splitting up into individual fruits instead of massive compound balls, or there will be a random mutation that encourages aggressive suckering and asexual reproduction. Maybe another animal will start to take advantage of osage orange fruit, filling the gap left by the giant sloth ten million years ago--at least in part. Maybe it will eventually be rendered extinct, except for a few specimens kept somewhere for study.

Right now, it's a plant that's almost irrelevant. Nobody plants hedgerows anymore. The osage orange grows too big, too fast and too messy, and pruning it makes it grow sharp thorns, only desirable when you want to keep someone out. Humans can't eat the fruit. Nothing eats the fruit--except for sometimes a hungry squirrel who will gnaw through the tough skin to the seeds and bitter flesh. It's been rendered irrelevant by the evolutionary niche that made it successful before collapsing. Human activity opened its range back up, but it's temporary or it will be an ever-present crutch. It has no independence; but then, it never really did. It was reliant on the sloth, and then it was reliant on humanity.

None of us are truly independent.

But humanity is not slowly fading out of the world because it doesn't fit anymore. Humanity is not--as of now--growing increasingly marginalized.

It's a little sad to think of something that was once successful, in every sense of the word, biologically and evolutionarily and otherwise, even a plant that's well-known and well-recognized for its fruit--the osage orange is a relic. It's a scientific term, one that matches the common definition in many ways: something no longer important, dead and gone and buried. An evolutionary trait that has been rendered irrelevant, even if the organism still persists. For now.