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September 18, 2005

What's owed to those who have gone before

We carved up the first of the kabochas from the garden last night. You can see it in the photo at left. Becky put wedges of it in a roasting pan with potatoes and carrots. She impaled a chicken with with half a dozen skewers of Tuscan rosemary I cut from the garden in the dark, wrapped it in a few strands of fresh-cut caraway thyme and put it atop the vegetables in the pan.

It was not the first thing to have come out of the oven in the new kitchen. There were the two dozen box-mix cupcakes for her class' Katrina fundraiser, which overall netted about three hundred bucks. There was the pan of brownies last week, when Jamie and Bill and kids stopped in from Olympia. I see them far too seldom.

The kabocha was rich and slightly overcooked, flesh like dry egg yolks. Sans chicken fat, it would have been a good base for ice cream or creme brulee.

Kabocha is the generic Japanese name for hard-shelled ("winter") squash in the species Cucurbita maxima. Genus Cucurbita contains summer and winter squashes, pumpkins and a couple gourds. There are five cultivated species and a few wild ones. The species divisions have little relation to the type of squash. Zucchini, acorn squash, spaghetti squash, the common Jack O'Lantern-type pumpkin, and butternut squash are all members of the same species, Cucurbita pepo. Cucurbita moschata - a more tropical species - exhibits similar diversity, including more butternuts. Like the difference between salmon and trout, the diversity among squashes is more a matter of taste than taxonomy.

Cucurbitas share a few important characteristics. Their plants grow both male and female flowers. Their fruit is the kind botanists refer to as a "pepo," a berry with a rind that is usually thick. (Summer squashes have had their thick rinds bred out.) The ancestral Cucurbita likely had a hard rind and very bitter, thin flesh at maturity, more gourd than pumpkin, like the coyote melon (Cucurbita foetidissima) of the American southwest. It's likely that early farmers first grew squash for their tasty, oil-filled seeds, selecting for sweet-flesh over many generations.

Eating kabocha last night, I was reminded of pronghorns. This is not as incongruous as it sounds.

Pronghorn, also inaccurately called antelope, live in the arid landscapes of the western US. They are grazers and browsers, live in irascible small groups or solitarily, and are faster than any historic predator large enough to threaten them. They are faster, in fact, than some trucks I have owned. Why would natural selection create a species that can outrun the fastest predator around without flicking an eyelash? Animals invest a lot of energy in being that fast, energy that is utterly wasted in being able to outrun pumas, wolves or grizzlies by twenty miles an hour. Five miles an hour would have done the trick. Evolution is conservative, usually giving a species just enough of an edge to survive long enough to reproduce. Pronghorn's speed comes at the cost of metabolic energy that could have been invested in reproduction, digestion, or just plain growing fat for the winter. It makes no sense.

Until you learn that North America, until relatively recently, had cheetahs living in it. Closely related to their African cousins, they were likely every bit as speedy. "A little faster than a cheetah" is faster than a bear by a wide margin. Pronghorn are only as fast as they once needed to be. Zoologist John A. Byers encapsulates this relationship elegantly in the title of his book on pronghorn: American Pronghorn: Social Adaptations And The Ghosts Of Predators Past. Pronghorn run from the ghosts of cheetahs. The pronghorn's gait is an example of a phenomenon called "coevolution," in which two species evolve in tandem. Pronghorn get faster, so the cheetah must get faster to catch them, so the pronghorn must get even faster to escape them. Now that the cheetah are gone - likely killed off by the first human hunters to roam North America, or their granchildren - this coevolutionary relationship has a missing partner.


Though kabocha is a Japanese type of squash, C. maxima originated in South America. It was imported to Japan sometime in the last five hundred years. The species includes more than two hundred varieties of pumpkin and winter squash, including the giant Hubbards.

Plant evolution is every bit as responsive to neighboring species as animal evolution. Perhaps more so, as many plants utterly rely on animals for reproduction. Succulent fruit is a means by which plants attract animals to disperse their seed. Brightly colored berries attract birds, who eat the sweet flesh and fly off to excrete the seeds therein - conveniently wrapped in a bit of fertilizer. The ancestral kabocha - a hard, bitter rind, acrid flesh, and dozens of sweet, oily seeds within - must also have evolved as a way to attract animals.

But what animals?

The seeds are sweet, but delicate. If the animal did more than swallow them whole, they'd be destroyed. So rule out rodents gnawing through the hull to get at the seeds. Rule out, for that matter, slightly larger animals, wolves and coyotes and tapirs and whatever other dog-sized animals might have ranged Pleistocene Argentina. Even a nick of tooth on seedcoat would expose the embryo to harsh stomach acid. That explains the bitter-tasting flesh and hard shell, deterrents to animals who could not swallow the squashes whole, so that they could digest the flesh without tasting it, then later excrete undamaged seeds in a pile of nutritious dung.

Imagine an animal that could swallow an acorn squash whole, without chewing. Where they live next to farmers in Africa, elephants regularly slurp down entire fields of squash, but no elephants ever lived in South America, even during the times of mastodons in Los Angeles. South America had camelids and horses, but they're too small. Squashes generally grow out of the reach of whales. Who, then, drove the evolution of the ancestral kabocha?

In my Joshua tree-related reading over the last decade, I've regularly encountered a cute little critter known as the Shasta Giant Ground Sloth, Nothrotheriops shastense, whole sole surviving close relative is the South American tree sloth. The last Shasta ground sloth died probably 12,000 years ago, when the Mojave was full of freshwater lakes and Yosemite of ice. Probable cause of extinction: the Clovis point. Until it was killed off, Nothrotheriops was a slow, shambling creature with fearsome claws, about the size of a large cow, that ate leaves and fruit in the desert southwest. Twelve thousand years is a long time, but it's not so long that some ground sloth dung doesn't still exist. In caves where there has been some protection from the elements, Shasta ground sloth dung has been preserved, and graduate students assigned the unenviable task of inventorying it. The sloths ate Joshua trees, juniper berries and twigs, and numerous other plant foods. They ate cactus fruits: the saguaro, which grows luscious, sweet seed-filled fruit atop tall spiny stems, may well have coevolved with Nothrotheriops.

(Incidentally, readers should watch this space for an upcoming, exciting Nothrotheriops-related development.)

As far as I know, there were no Nothrotheriops living in Pleistocene kabocha habitat. But the Shasta ground sloth had a cousin there, Megatherium americanum, who at 25 feet or so in height massed more than do many elephants. They ranged from the Southern Cone to present-day Texas. They had bony nodules on their skin, an effective armor against smilodons, nimravids, and the thylacosmilus, a marsupial "cat." All three animals had dagger-like carnassial teeth. Far smaller than Megatherium, the sabre-tooths' only hope for a kill would have been to ambush and stab, then wait from a distance while the sloth bled out.

I can only conjecture that Megatherium popped squashes into her mouth like candy. Then again, I can't imagine who else might have. Hundreds of generations of sloths, tens of thousands of generations of squash, and then humans showed up. They killed the sloths, ran out of meat, discovered the squash's tasty seed, began to plant the seed themselves, found a few squashes that had thicker, sweeter flesh, and saved those seeds preferentially. In an evolutionary eyeblink we had pumpkin pie, butternut squash soup, and kabocha tempura.

Much of human evolution has consisted of leveraged buyouts of coevolutionary partnerships. The same people who killed the ground sloths and mastodons, the dire wolves and short-faced bears, found themselves the possessors of incomplete ecosystems. They planted squash among the corn. They burned the prairie forests that were once uprooted by mammoths. They took long saguaro ribs, knocked ripe cactus fruit into baskets. Eventually, after a long time, a sort of equilibrium was achieved. A word to the wise, if there are any with the wisdom to heed it.

Two more kabocha swell on their long vines in my garden. The first one picked, they now grow all that much faster. Last night I delved the compost bowl, pulled out a dozen seeds, cleaned and dried them. They sit on a white china plate on the counter. They are tiny sparks of life, roots a billion years old. The genes within have been cooked in the guts of giant monsters. They will grow next summer, and I will save their seeds in turn, and welcome the ghosts of Megatherium as they reach for the top of the trellis.

Posted by Chris Clarke at September 18, 2005 08:15 AM TrackBack URL for this entry:

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I remember reading somewhere a theory that Megatherium americanum was a carnivore, based on the claws and the absence of specialized chewing molars. Your theory sounds more plausible, if only because I find it hard to imagine a killer sloth.

Posted by: Jim McCulloch at September 18, 2005 11:27 AM
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if only because I find it hard to imagine a killer sloth.







Posted by: Chris Clarke at September 18, 2005 11:32 AM
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can we assume your new kitchen is finished?

i like the idea of rosemary skewers. i often put a large sprig of it on the barbecue with chicken or fish. thanks for the botany lesson on squashes. i have noticed, growing both this year, that acorn and zucchini squash plants look quite similar.

Posted by: dread pirate roberts at September 18, 2005 01:24 PM
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My favorite simple roast chicken involves putting a large branch of fresh rosemary in the cavity of a whole chicken. Sometimes I add a cut up onion also. It produces the most amazingly flavored chicken.

Posted by: alice at September 18, 2005 01:31 PM
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Kitchen is close to finished. Still needs knobs, a firedoor, and a refrigerator. A couple pieces of trim here and there.

Posted by: Chris Clarke at September 18, 2005 02:41 PM
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My god (pardon the expression), how did you go from cooking to gardening to Pleistocene evolution and predators to delving into the oft overlooked evolution of plants, end up in the compost heap, and remain completely fluid and riveting?!?!?! Not just anybody can pull that off. The downside is, now I have to run to the store to pick up some rosemary, chicken, and squash . . .

Posted by: Jamie at September 18, 2005 06:01 PM
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end up in the compost heap,

We all do eventually.

Posted by: Chris Clarke at September 18, 2005 06:16 PM
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We all do eventually.

Good point, and pity de fool that don't see the beauty in that. You should write books; we'd buy them. But that's probably one of those things you hear so much it gets annoying. That is all.

Posted by: Jamie at September 18, 2005 06:56 PM
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Agh, Jamie stole my comment!

So... new kitchen? What's this about a new kitchen? Did I miss a post somewhere?

Posted by: Rana at September 19, 2005 10:56 AM
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No, Rana, no missed posts. I didn't really feel much like talking about our new kitchen in the last few weeks, for some reason.

Posted by: Chris Clarke at September 19, 2005 11:03 AM
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Hey Chris, I illustrated that predatory ground sloth story in Discover magazine back in the mid 90s. It was based on an interesting paper by an (I think) Argentine paleontologist, but most/all of his colleagues didn't share his conclusions.

And actually there were three (?) genera of Proboscideans that did reach S. America in the Pliocene/Pleistocene; Haplomastondon, Stegomaston and Cuvieronius, the final two lasting until the arrival of man, but the big ground sloths had a much longer history with the squashes.

Posted by: OGeorge at September 21, 2005 06:41 PM
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