Wednesday, February 24, 2010

Evolution and Food - The Red Queen Principle

“Well, in our country,” said Alice, still panting a little, “you’d generally get to somewhere else – if you ran very fast for a long time as we’ve been doing.”

“A slow sort of country!” said the Queen. “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

“I’d rather not try, please!” said Alice. “I’m quite content to stay here – only I am so hot and thirsty!”

~ Lewis Carroll, Through the Looking-Glass



Animal, Vegetable, Miracle: A Year of Food Life is Barbara Kingsolver’s biting, articulate, persuasive bill of particulars against agribusiness for what she finds wrong about how most of the food is produced, distributed, and marketed in this country and now throughout much of the world. The agribusiness villains of the piece are damned for, among other sins, their concentrated animal feeding operations for which the adjective “cruel” is too mild, and their genetic modification of our food plants, a pernicious process protected by a legal framework that turns reason on its head.

I just finished reading this nonfiction volume (published in 2007) and, though Kingsolver ranks among my favorite novelists, particularly for the novels she wrote early in her career like The Bean Trees and Pigs in Heaven, and I have been moved by those novels, only this book of hers has caused me to rethink aspects of how I live my life. Hard to give a writer higher praise, I think. And there’s some interesting and important science here, too (or else how could I justify putting this post in this blog).

(I know I'm coming late to this book and this subject. If some venting on this subject isn’t of interest – which occurs both in the book and in the rest of this post – my apologies. Hope to see you next time.)

Animal, Vegetable, Miracle is the account of a year in which Kingsolver, her husband Steven Hopp (who contributes a number of background pieces to the book), and daughters Camille (who contributes recipes and stories of food) and Lily seek to free themselves from the reach of agribusiness by growing as much of their food – animal and plant – as possible on their small farm in Virginia, and by buying from farmers in their local area. The struggles and triumphs of that year are set against descriptions of the devastating impact of agribusiness on our food supply, our health, the nation’s small farmers, and our local communities. Theirs is an inspiring saga (that of agribusiness, not so much) and, frankly, there’s hope that a change in attitude is taking hold in the general population that will, in turn, change what we eat for the better.

Kingsolver’s message is summed up by Tod Murphy, the owner of the Farmers Diner. (At the time the book was written, the diner was in Barre, Vermont, but the operation has expanded and been relocated to Quechee and Middlebury, Vermont.) The Farmers Diner is of its local community – serving food made from local produce and meat. Murphy’s motto is:
Think Locally, Act Neighborly

In other words, a key to fixing what’s wrong with our food supply is to shift our focus to what’s grown in our extended neighborhoods and, short of raising our own food (well, perhaps trying to do a bit of that), this means buying as much food grown locally as we can, produce grown for taste not for its ability to endure many days and thousands of miles in transit. Our charge is to let local grocery stores know our preferences for fresh, local produce, shift food dollars to farmers’ markets, find alternatives to processed foods.

Why is changing our food habits so tough to do? Yes, we have multi-billion dollar conglomerates aligned against us and our best interest. But, more intriguing to me, is Kingsolver’s assertion that we are victims of evolution and that evolution helps explain why junk food accounts for about a third of our calories. She writes,

. . . humans have a built-in weakness for fats and sugar. We evolved in lean environments where it was a big plus for survival to gorge on calorie-dense foods whenever we found them. Whether or not they understand the biology, food marketers know the weakness and have exploited it without mercy. (p. 15)

Evolution plays other critical roles in the mess that we’ve created in our food supply. For example, the arms race between insect pests who attack food plants and the scientists creating ever stronger pesticides that enter the world’s food chain is one that the powerful evolutionary engine is bound to win. Hopp cites the following damning statistics: In 1948, farmers applied 50 million pounds of pesticides and suffered a 7% loss rate of their crops. In 2000, a billion (that’s a billion with a “b”) pounds of pesticides were applied and the loss rate was . . . 13%. His solution: “Organic agriculture, which allows insect predator populations to retain a healthy presence in our fields, breaks the cycle.” (p. 165) [Later edit: Hopp's data apply to U.S. farmers.]

Even more troubling to me is the loss of diversity in our crop plants. Kingsolver, who did graduate work in evolutionary biology, lays it out clearly. This is where the Red Queen principle spells trouble. A descriptive label drawn from Through the Looking-Glass, it was first used by evolutionary biologist Lee Van Valen to describe the constant evolutionary point-counterpoint that marks the relationship between predator and prey in which the former evolves to gain a small advantage only to have it countered shortly by a change in the latter – a never-ending process (well, we hope it’s never-ending), one involving running as fast as a species can in order to stay alive and propagating in the same place. Our crop plants and disease are co-evolving, locked in a struggle for survival, but the loss of diversity in the former takes potentially vital genetic variety out of the plant arsenal, leaving plants at risk of being unable to respond to the newest development in the disease community. Kingsolver points to the Irish potato famine as but one example of how the danger may play out. Today, agribusiness has ensured that just a few varieties of corn and soybeans are the source for many of our calories. As she puts it,
Our addiction to just two crops has made us the fattest people who’ve ever lived, dining just a few pathogens away from famine. (p. 54)

How much of change this book will make in my food habits is an open question. There are a few small signs that something’s stirring, but only time will tell. A couple of days ago the seductive smell of baking bread, made from scratch, drifted through the house for the first time in probably 15 years. As I waited for it to be done, I ate slices of Rome apples (admittedly, not an adventurous choice) grown in an orchard some 117 miles up the road, and, later, I made a meat loaf for dinner using free range turkey from a farm in the same direction up that road. It’s a beginning.

Oh, of course it’s particularly hard to start down a path like this in late February. Fresh, local produce? Our local farmers’ markets wont really get going for roughly another couple of months. And I don’t have a freezer stocked with produce from the past summer. Kingsolver speaks directly to me in this situation:
Eating locally in winter is easy. But the time to think about that would be in August. (p. 309)

A grand book (with a useful website).

Postscript [added later]

A current Wired magazine article highlights the importance of maintaining genetic variety among our crop plants, telling the dramatic story of the fight against the Ug99 stem rust fungus that has devastated wheat crops in Africa, moved into the Middle East, and may have set its sights on China and India. (Red Menace: Stop the Ug99 Fungus Before Its Spores Bring Starvation, by Brendan I. Koerner, Wired, March 2010). In a great deal of the wheat raised worldwide, the line of defense against stem rust consists of the Sr31 gene, bred into wheat from rye during the Green Revolution in the latter half of the 20th century. Now, with the emergence of the Ug99 pathogen (discovered in Uganda in 1999), this line of defense has been breached and wheat production worldwide is threatened. Too many eggs in one basket, it appears. It is fascinating to read of scientists scouring the world for wheat varieties that can be tested for resistance to Ug99, to the point of raiding a collection of seeds gathered during the 1930s from wild wheat varieties (yes, there is a reason to encourage the gathering and planting of seeds from heirloom varieties of plants). The hope now? Diamondbird wheat is proving resilient, able to contain stem rust, and, in contrast to the wheat strain with Sr31, this wheat has an array of minor genes manning its defenses – apparently a better tactic than the one that scientists previously relied on. Altogether, a compelling argument to stem the mounting loss of genetic variety in our crop plants that apparently has accompanied U.S. food policy over the last half century.

Monday, February 15, 2010

On The Cutting Edge

The entire ocean is a tomb and I a tooth.

~ from the poem “Shark” by Richard Grossman



Playing Around

How to capture the image of a fossil continues to frustrate me. Would that I could draw like those 19th Century artists who specialized in fossils, artists like Joseph Dinkel. But, absent the necessary talent, I rely on digital photography supplemented on occasion by amateurish sketches. Lately, though, I’ve been playing around with Inkscape, a free vector graphics drawing software program. Working from photographs, I created the two profile images (below) of a fossil tooth from a sand tiger (Striatolamia striata, Paleocene epoch, about 60 million years ago).These images precipitated an exploration of the cutting edges of fossil shark teeth – certainly nothing avant-garde or truly cutting edge about my efforts. As will become evident, this exploration triggered mixed emotions. (In these drawings, the cutting edge on either side of the tooth is the middle dark line that tracks up the crown, beginning about a third of the way up from the root. The tooth is approximately 1 7/16 inches long and somewhat worn.) [Later edit: I should have noted that the drawings don't show how the lower two-thirds of the crown is striated, a hallmark of teeth from this species. The striations are faint, probably due to wearing, and mostly do not appear in the photos upon which the drawings are based.]



Cutting Edges of the Shark Kind

The cutting edge on a shark tooth is a more or less prominent ridge that can run down either margin of the crown and was “developed for slicing flesh” (Kent, p. 92 – full citation below). As best I can figure, there are two basic types of cutting edges on shark teeth – smooth and serrated. Each type comes in various flavors. For example, cutting edges may extend the complete length of the crown margins or just some portion of them. Serrations, described by Frazzetta as “a series of small projections or scallops” that run down side of the crown, may be simple or complex (p. 97 – full citation below). The latter are serrated serrations.

The picture on the left below is of a fossilized tooth from a snaggletooth shark (Hemipristis serra) with simple serrations that stop before reaching the top of the crown, conveniently leaving a point for puncturing flesh (the serrations are then in a great place for major cutting). The picture on the right shows a fossilized tooth from a tiger shark (Galeocerdo cuvier) with a closeup of the serrations on the shoulders of the crown. Examined closely and it’s evident that the serrations are serrated. Both of these specimens are from the late Miocene epoch, about 5 mya. The third picture below is of a modern Galeocerdo cuvier – the serrated serrations are much clearer on this specimen.













S. striata With A Twist


There is a complex diversity in cutting edges, influenced greatly by overall tooth shape. I wont go into that here, other than to return the two drawings above of the S. striata tooth. These drawings highlight a feature of the shape of the teeth (particularly the anterior ones) from this sand tiger species and others – they can be gracefully sinuous – often described as sigmoidal. From the root, the crown first curves out, away from the tongue (the prominent protrusion in the root points toward the tongue), then arches back and, finally, at the apex, bends toward the lip. Frazzetta observed this “reverse curvature” at the tip and likened it to the shape he saw in the teeth of pythons and boas, and some viper fangs. The general shape, apparently, is useful for penetrating and holding.

I wonder if there aren’t some interesting tradeoffs in developing these curved teeth, beyond the mechanics of their use. Presumably, the curvature allows for a longer cutting edge on a tooth that doesn’t take up as much vertical space, perhaps allowing them to fit in a smaller mouth. More bang for the buck? Just a thought.

The very process of capturing an image of a fossil, whether it’s by drawing or photographing, sometimes forces me to register features for the first time. In this case, it was the puzzling aspect of the S. striata tooth – a difference in the cutting edges on either side of the crown. In the drawing on the left above, the cutting edge has a final, little twist at the apex, seemingly joining the lingual side of the crown; while, in the drawing on the right above, the cutting edge appears to become one with the labial, relatively flat side of the crown. I’ve reproduced the first drawing below with the twist circled.




It’s not a function of the drawings; it’s really in the tooth and, in my limited experience, this twist isn’t unique to this particular specimen of S. striata, nor to just this particular species of sand tiger. There are two issues actually – why does the cutting edge do this little flip or twist only on one side of the crown, and why have I not seen it described in the literature?

Maybe I haven’t looked hard enough or smart enough. My tried and true references appear to be silent on it. I had high hopes for Cunningham’s article on the dentition of Striatolamia macrota (full citation below – it’s relevant since some folks argue that S. striata is the same species), but, the twist doesn’t appear.

Surrounded by Cutting Edges


I mentioned Frazzetta’s work earlier. It’s intriguing as much for the methodology as for the analysis. He found no available literature on how cutting edges rend materials that are flexible, that is, have give to them, materials such as, oh, say, . . . flesh. So, to explore how shark teeth do their deadly deed, he gathered various smooth and serrated metal blades, including saws, and then closely observed the mechanics of what happened when the cutting edges were brought to bear on such organic materials as fish, cow leather, and shark skin, and on some inorganic materials including paper and cloth.

His article triggered the sickening realization that I am surrounded by cutting edges.

At this juncture in this Mid-Atlantic winter of our discontent, the cutting edge on the snow shovel I’ve been using has been worn dull. Given that it’s plastic, it has suffered from encounters with ice, concrete, and asphalt. The other morning, as I walked through my garage to get the shovel, I passed two band saws hanging on the wall. They’d been doing their job as recently as a couple of weeks ago, cutting up some of the limbs and branches from three (I think) trees that came down in the farthest reaches of my backyard during a day of high wind (not knowing for sure how many trees fell suggests the extent of the mess and, of course, all parts of said backyard are buried under more than three feet of snow). Back in those pre-snow days, the jaggedly notched cutting edges of those band saws tore through pine and locust, scattering sawdust, and on occasion catching on my gloves. At that point, hidden and protected in my right glove was a bandaged finger, nicked as I prepared dinner a few days earlier, a thin serrated knife failing to distinguish chicken from human flesh.

Just consider the myriad utensils in the kitchen drawers, the edges of the boxes in the pantry that hold plastic wrap or wax paper, the razors, scissors, and clippers waiting in the bathroom. Wander through the house, they’re everywhere. A mouth full of teeth, probably the most varied collection of different cutting edges each of us typically has. All of this designed to puncture, tear, rip, break up (and down) . . . . Nasty, brutish.

It is extremely absurd that I hunt for, and have drawers full of, fossil shark teeth, objects with wonderfully efficient cutting edges, cutting edges that I find quite beautiful . . . on shark teeth. To be honest, cutting edges and I should not mix. I do very poorly at the sight of blood, I even blanch at reading those poems by Sylvia Plath (“Cut”) and Robert Frost (“Out, Out – ”), and . . . point made. I’m already feeling faint.


Sources

Henri Cappetta, Chondrichthyes II: Mesozoic and Cenozoic Elasmobranchii (1987)

Stephen B. Cunningham, A Comparison of Isolated Teeth of Early Eocene Striatolamia microta (Chrondrichthyes, Laminformes), With Those of a Recent Sand Shark, Carcharias taurus, Tertiary Research, June 2000

T.H. Frazzetta, The mechanics of cutting and the form of shark teeth (Chrondrichthyes, Elasmobranchii), Zoomorphology, Vol. 108, p. 93-107, 1988

Bretton W. Kent, Fossil Sharks of the Chesapeake Bay Region (1994)

Wednesday, February 10, 2010

Warring Nature

The inanimate works of nature – rock, ice, snow, wind, and water – all warring with each other, yet combined against man – here reigned in absolute sovereignty.

~ Charles Darwin, The Voyage Of The Beagle, June 8, 1834.


Darwin was describing a cove near Mount Sarmiento in the Chilean portion of Tierra del Fuego. Yet, as the second blizzard in five days rampages here, it could just as well have been somewhere in the Mid-Atlantic States.

On the Chesapeake Bay, perhaps.

I wonder what fossils are now tumbling in the inaccessible surf beneath the Calvert Cliffs.

Saturday, February 6, 2010

Type Specimen Amid the Tubas

This post is about a fossil, a type specimen, whose story is interesting on its face. Still, there seemed to be such potential for more that I spent time tracing back some of its details. In the process, I learned a bit about a geologist of the first half of the 20th century, and about a Texas town’s use of local stone in its buildings. But, in the end, I came back to the original story with nothing profound to tie all the pieces together. Sometimes the parts don’t make a whole. So it goes.

Terminology and Expectations


Type specimen is the specific specimen upon which the description of a new species is initially based. It is usually chosen by the person naming a new species as “the standard of reference to represent his or her concept of that species.” (Donald R. Prothero, Bringing Fossils to Life: An Introduction of Paleobiology, p. 59.)

Given the importance of these specimens, Prothero also observes:

Normally, type specimens are deposited in a major museum or other reference collection with scientific access, so other scientists can examine them. (p. 60, emphasis added)


Then, again, this expectation may not be realized because a type specimen may not end up in a museum or any collection at all. It may have to stay where the person doing the naming found it, wherever that might be. And that wherever may drastically change who has access to it.

Wherever

In the early 1930s, a slab of limestone containing a dramatically well-defined, three-toed dinosaur track was cut out of the bed of the Paluxy River, at the so-called “fourth crossing” of the river, a spot some six miles west of the Texas town of Glen Rose. This piece of Cretaceous period limestone, replete with dinosaur track, was then incorporated into the wall at the base of the town’s bandstand in front of the Somervell County Court House, where it remains.

In 1934, a year after it became part of the bandstand, geologist Ellis W. Shuler from Southern Methodist University visited the dinosaur track. He returned a year later with a small team to examine the track more closely. Measurements were taken (25 inches from heel to end of the middle toe, and 17 inches across the toes) as was a cast. Shuler shot the picture below.



Presumably based on, among other details, the features of the foot revealed by the track and the overall length of the stride (the track was one of a series of four in the riverbed), he concluded:

The individual dinosaur making the track was most certainly of the flesh eating type, catching its prey by high bursts of speed. The name Eubrontes (?) glenrosensis sp. nov. is suggested for this species.

~ “Dinosaur Track Mounted in the Band Stand at Glen Rose, Texas,” by Ellis. W. Shuler, Field and Laboratory, Volume 4, Number 1, November, 1935, p. 13

In one fell swoop, Shuler both gave a name to this ichnofossil (trace fossil) and took it back, well, at least, partially. (He was naming the trace fossil, not the animal that actually made the track.) The question mark following Eubrontes denotes doubt that this ichnofossil belongs to the Eubrontes ichnogenus. And, apparently, there remains some doubt among paleontologists today.

Shuler

As I wrote this out, I realized there has been a recurrent feature in this blog -- small biographical portraits of the people who do science, particularly paleontology.

I assume that Ellis Shuler, as one the first faculty members hired at Southern Methodist University in 1915, initially constituted the entire geology faculty at the institution. The Harvard-trained Shuler served at SMU for 35 years, retiring in 1952, the last of the original hires to retire.

The roots of his attraction to geology and paleontology lie in his childhood in Virginia. It’s a story recounted in the opening of his book, Rocks and Rivers (1945):

My first lesson in geology came in singular fashion. A boy of fourteen, I had just finished reading The Last Days of Pompeii when a series of earthquakes shook the little town of Pearisburg, Virginia, where my father preached.

This was probably in 1895. His father prevailed on the U.S. Geological Survey to send a geologist to look into the origins of the earthquake. Marius R. Campbell arrived and reassured the boy that a volcanic eruption was not imminent. Campbell then joined the Shuler family as they journeyed to a summer resort up near the top of Salt Pond Mountain. They trekked by foot along a road up the mountain. Recalled Shuler,

As I tramped barefooted by his side, Mr. Campbell discovered for me a new world in the shale beds by the roadway.

“These are fossils, sea shells,” he said.


With Campbell’s guidance, the boy filled his pockets with fossils, some quite rare.

The following day, boy and man stood at the top of the mountain. Campbell set up a camera to capture the vast landscape of river, valley, lake. Shuler asked, “Mr. Campbell, what makes mountains?” Campbell looked at the boy and said, “You are a funny kid.” And then proceeded with a lesson in geology.

Beautiful.

I have to assume that Shuler intended Rocks and Rivers to be one of the crowning achievements to his career. It may well have been. An accessible, somewhat technical exploration of different key features of the natural geological landscape, the book clearly was a labor of love. Given the dry and fact-driven writing that he saw permeating professional writing in this science, Shuler set out to do something different. The book, he wrote, was “an adventure” and he hoped “that the romance and occasional levity in this volume may be pardoned.”

But, it has not aged well, I fear. When I first learned about Rocks and Rivers, I lost little time finding it in a used book store, hoping it would be an unheralded treasure. If only the tone, style, and intimacy of “A Personal Foreword” which opens the book (and is the source of the quotations above) marked the entire effort, any dated geological explanations would not have been sufficient to condemn the book to the out-of-print and unread world where it now resides. Among other limitations, without benefit of the theory of plate tectonics, it struggles for explanations of some landscape features. Still, I did like parts of the book besides the Foreword, including a chapter on glacier action shaping the landscape. A very solid treatment of that subject as far as I can tell. Alas, though, for me, those few, intimate, almost lyrical pages of the Foreword, which are the highlight of the book, promise much that isn’t delivered.

Buildings in a Small Town

What’s missing in Shuler’s picture above of the track inset in the bandstand wall is any hint of what surrounds the slab of limestone. The entire base of the bandstand has a facade of inlaid pieces of petrified wood.



Petrified wood turned up so frequently in local farmed fields that, beginning in the 1920s, it became a common decorative material for buildings in the Glen Rose area, being used in buildings ranging from homes to hotels, from restaurants to gas stations. The county courthouse behind the bandstand shares in that town custom. Indeed, this decor for buildings in Glen Rose is so common that the town, reportedly, is known as the “Petrified City.”

Back to the Wall

An outdoor bandstand is probably not the best place to keep a type specimen. After three-quarters of a century of exposure, this piece of Glen Rose limestone, laid down in the Cretaceous, is eroding. And with this erosion, details of this type specimen of Eubrontes (?) glenrosensis are fading.



But, still, for 75 years, this type specimen has been available for study by anyone, and I mean, anyone – tuba player or tuba lover or . . . .

I wonder whether other type specimens have been this accessible.



Postscript and Credits


In an effort to preserve as much detail of the fossil as possible in its present condition, SMU paleontologist Thomas L. Adams has used a portable scanner to create three dimensional digital models of this specimen. It was news coverage of his work that first interested me in Eubrontes (?) glenrosensis and Ellis Shuler. Photographs in this posting are by Ellis Shuler and Thomas L. Adams of SMU. They are reproduced by permission, and appear in the SMU Research blog in the 2009 article entitled Portable 3D laser technology preserves Texas dinosaur's rare footprint by Margaret Allen.

Other Sources


An interesting look at the town is provided in Glen Rose, Texas, by Gene Fowler and the Somervell County Historical Commission, a book in the Images of America series, 2002.

Dinosaur Valley State Park is near Glen Rose and abounds with dinosaur tracks. The site is managed by the state of Texas’ Parks and Wildlife Department. A brochure can be found here.

The Park is also a National Natural Landmark, participating voluntarily in this U.S. National Park Service program. A brochure about the Landmarks and the program can be found here.

Of interest (and a subject I chose not to get into) is On the Heels of Dinosaurs: An Informal History of the Texas "Man Track" Controversy by Glen J. Kuban. Link here.
 
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