What is the Grass? Watching How to Grow a Planet

A child said What is the grass? fetching it to me with full hands;
How could I answer the child? I do not know what it is any more than he.

—Walt Whitman, “Song of Myself,” st. 6

Grass short cell phytoliths in silificied epidermis from Late Cretaceous coprolites from Pisdura, India. Scale bar = 10 micrometers. (See http://depts.washington.edu/strmbrgl/StrombergLab_website/R_Poaceae_evolution.html)
Microscope image of fossilized grass found in a dinosaur coprolite (i.e., a fossil feces). This specimen dates from the Late Cretaceous, about sixty-five million years ago. Scale bar = 10 micrometers. (See the short post here, from the Burke Museum of Natural History and Culture, Washington University.)

Last Thursday night found myself mesmerized by a documentary on TVO about grass. Like, absolutely glued to the set with my mouth hanging open. Now, I’m sure you need a moment to back up off the edge of your seat, so take all the time you need.

StewartThis was the final episode of a three-part series from the BBC called How to Grow a Planet, hosted by geologist Iain Stewart. This episode, entitled “The Challenger,” follows Stewart from the ancient cloud forests of Kenya to a South African national park, from the mid-western United States to Senegal, and, finally, Göbekli Tepe in Southern Turkey.

I strongly encourage you to check out this series, so I won’t get into all the details here.  Suffice to say that “The Challenger” follows our hero as it battles trees for dominion over the vegetable kingdom on terrestrial Earth. It’s like Game of Thrones for the horticultural set. Things start to hit close to home near the end of the episode, when grass is held up as the prime mover of hominid evolutionary and cultural development.

One of the prevailing rhetorical tactics that the series employs is a fairly consistent language of agency, intention, intelligence, and design applied to plant life and evolution in general.  Most notable in “The Challenger” is an extended discussion of the cellular “turbo charger” developed by grasses to enhance their consumption of carbon dioxide at a time, approximately thirty-million years ago, when C02 levels in the atmosphere dropped to one-sixth of their previous concentration.  Stewart goes out of his way to draw the analogy between the (biological) technology “discovered” by grass and a turbo-charged automobile engine, opening and explaining the operation of the engine inside his truck before computer graphics look under the hood of a grass leaf to display this biological “invention.”

At first the decision to give so much agency and intentionality to plants irked me.  “Grasses were evolving a new and surprising invention.”  “Grasses exploited fire.” “Evolution provided often comes up with the cleverest solutions in desperate times.” “Grasses turned crisis into opportunity”  I guess I was put off by the “anthropomorphic” fallacy that was ascribing autonomy to automatic processes. (As Tom Tyler points out, however, the charge of anthropomorphism is itself a product of our own anthropocentric species-bias…but I digress.)

Somewhere about mid-way through the episode, the ongoing fallacy started to lay bare the series’ prevailing mandate, and the stakes of the argument became very compelling. After describing a number of changes and circumstances that led to the revolutionary succession of grass over tree about seven-million years ago, Stewart shifts the discussion to the ways in which “the global rise of grasses…was transforming the animal kingdom, too.”

Dismounting a horse on a North-American plain, Stewart kneels down, tears off a hearty grass blade and wrenches it through his palm, cutting his fingers as he does so.  As he thrusts his bleeding finger into the camera, he explains that grasses developed defensive weapons to help ward off hungry herbivores: little daggers line the edge of each leaf, made from the silica that the plants absorb from the soil.  The consequences for the animals eating the grass weren’t so much about lacerations, mind, but rather the damage these mineral outcroppings wrought on their teeth. Par for the course, the plant is granted a certain technical intelligence, and we are treated to a retroactive explanation for the “purpose” behind an evolutionary development.  Yet the impact of this trait is discussed in an unexpected way.

Tiny silica "daggers" line the edge of a blade of grass.
Tiny silica “daggers” line the edge of a blade of grass.

Stewart describes how, in the space of only one-million years or so—a “geological instant”—something on the order of half of all herbivorous mammals became extinct across the planet. Those that survived developed more durable teeth and promptly altered their diets from tree leaves and shrubs to grasses. The entire sequence gives the impression that the animals were the passive subjects to the unquestionable agency of vegetation:

By six million years ago, the triumph of grasses had caused the death of many types of animals, while creating vast herds of new ones: the more familiar plant-eaters we know today.

Of course, this agency on the part of vegetable life flies in the face of thousands of years of Western thought. In the heirarchy of psukhe that Aristotle formulates in De Anima, vegetables possess a soul and a life that is merely nutritive.  Plants have the power to grow, consume, and finally die—end of story.  The animal soul builds on top of this capability, adding the power of movement and sensation, thus the capacity for certain degrees of autonomy.  But in How to Grow a Planet, animals are passive subjects to plants unquestionable sovereignty.  They are the hapless victims of powerful defensive weapons as well as the malleable forms upon whom the plants force a change. Plants are the arbiters of who lives and who dies, and the sculptors of teeth, flesh, and bone.

The stakes are immeasurably raised in the episode’s final act, in which grass becomes the driving force behind the appearance of hominids and, ultimately, the emergence of civilization.  First, Stewart visits the Fongoli chimps in Senegal, who live almost exclusively in grasslands of the area. These apes are adept tool-users, using long branches to pull termites out of logs.  They are also the only known apes to fashion spears out of sharpened branches, which they use to kill smaller mammals, particularly bush babies.  The show ascribes this behaviour to the relative scar­city of food resources found on the plains as opposed to forested areas.

The most visceral images come at the end of the Fongoli chimp sequence, as Stewart reviews video footage of one of the chimps standing up on two legs to catch a better view over the tall grass.  A number of times over the course of these ten minutes or so, he repeats the idea that he is witnessing a scene from four- or five-million years ago, when our ape-like ancestors first left the forests and moved out into the grassy plains:

Here at Fongoli you can actually see what scientists think happened when grasses shaped our ancient ancestors and encouraged them to take those first upright steps onto the savannah.

It was the episode’s final act, however, that was the most radical, as the influence of grass shifted from the natural and biological to the cultural and economic.  In the last ten minutes, Stewart travels to Göbekli Tepe an archaeological site whose importance to our understanding of protohistoric human societies cannot he overstated.  Discovered in 1994, Göbekli Tepe appears to be some sort of temple whose most striking remains are twenty-foot-high monoliths adorned with sophisticated flat- and high-relief sculptures depicting animals such as leopards and boar.  The existence of the ruins suggests a highly structured group of people, with a priestly caste and a large, organized workforce.  The thing is, Göbekli Tepe dates back to somewhere around twelve-thousand years ago, several millennia before the earliest civilizations.  These people should have been stone-aged hunter-gatherers, not a settled community undertaking such an elaborate engineering project.  And yet, there stand the monoliths, the fierce deities or totems that adorn them staring back from the cusp between the Paleolithic and Neolithic eras.

How Göbekli Tepe fits into the story of grass lies in the surrounding area.  Within a few dozen kilometres of the dig site, one finds wild strains of einkorn wheat.  Stewart takes us there and kneels down to pluck a stalk.  The grains immediately drop away, scattering over the ground at the slightest touch.  Of course, this is evolutionarily advan­tageous: once the seed is ripe enough, it can be blown or knocked away with ease in order to spread and propagate.  As Stewart demonstrates, however, this is not so hot for human consumption: trying to pick up the individual seeds proves painstakingly awkward.  Certainly this is not the resource that fed a workforce, several hundred men strong, over the centuries during which Göbekli Tepe were built.

Not far from the wild wheat, however, is another species, an ancient strain with a very small but decisive genetic mutation.  See, there is a little collar at the base of each grain of wheat that connects it to the stalk.  In the wild strain, this collar breaks down when the plant matures, making it brittle and easily broken so the seed falls free.  In the other species, however, this collar doesn’t break down.  It can thus be handled pretty roughly (Stewart smacks it against his open palm) and the seeds remain attached.  This seems detrimental to the survivability of the plant, but its resilience to manipulation makes it efficient to reap, to gather, to store, to apportion, to expedite. It could be refined and processed to make bread, an compact, portable energy source.  If Göbekli Tepe shows us a seedling form of “civilization,” it is only because, in this particular place, twelve-thousand years ago, there grew a kind of grass that lent itself to agriculture.    I love Stewart’s final word on the subject, which deliberately undercuts anthropocentric conceits of human technical mastery over the natural world:

There’s one last thing that I find intriguing.  Our ancestors must have felt that they were the masters of this new crop, the same way that we still feel today about farming: that we are in control of the plants that we grow and harvest. But think of it for a minute from the wheat’s point of view.  Now here’s a plant that has done something really clever.  It’s attracted an animal that is prepared to sow it, to nurture it, to protect it from competitors and scavengers.  It’s also prepared to disperse its seed by hand, without the plant having to do a single thing.  So it begs a question: who’s using who?

What we call civilization is the result of vegetable powers of attraction, an inter-species (rather, an inter-kingdom) seduction that led homo sapiens to new means and techniques of social organization. To consider, even for an hour, that the things that we as modern human beings esteem about our existence are thanks to grass and the potent agency of the vegetable world, is both profoundly disquieting and exhilarating.

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