Colors ~ Fossils and a Graphic Story About Darwin

This posting was prompted when I opened a drawer full of fossil teeth from Mako (Isurus) sharks, large and aggressive creatures, a genus of shark still with us.  I was surprised by the array of colors within this single drawer.  The color of fossils . . . yes, their palette typically shows much black, gray, and brown, but it can also glisten with blobs of many other colors, such as various shades of red, orange, and white.

Many factors influence a fossil’s hues and tones, including the mineral composition of the sediment within which the fossil-to-be is buried, the amount of organic material, bacteria, and oxygen in the surrounding matrix, the temperatures and amount of pressure applied during its millions of years of sequestration, and what it experiences upon exposure.  Curiously, the basic texts on fossils I consulted say little about this coloring process and, when they do, it is usually in the context of the permineralization of wood or perhaps bone, a process in which dissolved minerals in the surrounding matrix leach into the remains, filling empty spaces.  Different mixtures of minerals, different colors.

Paleontologist Bretton Kent (Fossil Sharks of the Chesapeake Bay Region, 1994) describes the origins of fossil colors:

Internal cavities and the microscopic spaces left in fossils by the destruction of organic materials can be eventually refilled by the precipitation of inorganic compounds, such as calcium carbonate, iron oxide and iron phosphate.  These minerals help stabilize the fossil, but also alter the color from the white of fresh bone, cartilage or teeth to the various earthy shades typically found in vertebrate fossils.  (p. 124)

The basic composition of shark teeth as described by Kent – roots composed of osteodentine and crowns composed of enameloid – offers the fossilization process two different canvases to work with, leading usually to at least a bicolor fossil.  Circumstances may offer the tooth a fuller palette.  The crown appears more susceptible to becoming multi-hued.  Here, then, is a sample of my colorful Makos.  Several species are represented here and the largest of the bunch are about 1 3/8th inches in length.

What makes this process all the more fascinating is how random the painting might be.  Fossils from the same species and from the same formation, perhaps even from within inches of each other, may emerge into daylight presenting different “faces” to the world.  Though their coloring differs, the story each has to tell of the species from which it came will be the same.  Their taphonomic (post-death) experiences . . . now those will differ.

In the picture below I’ve now identified the various formations from which these teeth came.  Each is from the Miocene (most are from around the 20 million year mark within that epoch which stretched from 23 million to 5 million years ago) with the exception of the tooth probably from the Yorktown Formation which is Early Pliocene (some 5 million years ago).  The two numbered teeth were found on the same day in just about the same location.  Of course, neither of these pieces of information has probative value for this story because they were found in the wash between the Chesapeake Bay and the Calvert Cliffs.  As a consequence, though these two teeth could have been initially exposed at the exact same time, they could just as well have emerged weeks, months, or even years apart.  Similarly, they may have fossilized in the Calvert Formation in almost the same, precise location but could have spent millions of years in spots several miles apart.  Still the circumstances of these finds serves, in my mind at least, to burnish the remarkable differences in coloring between these two teeth.

Simply because I’ve been reading it and there’s a little, related, quirky element to it, these musings on colors now involve Jay Hosler’s original and admittedly peculiar graphic story titled The Sandwalk Adventures:  An Adventure in Evolution Told in Five Chapters (2003).  The book explains the basic principles of evolution through drawings depicting a conversation between an old Charles Darwin and a follicle mite living in his left eyebrow (and this isn’t even the quirky quality I mentioned).

With the exception of the covers, the drawings in this book are intended to be wholly in black and white.  But my copy has a very small handful of drawings in the opening pages that are nicely colored.  Where there was intended to be a boring and limited palette, my book enjoys in little pockets a vibrant kaleidoscope of Crayola colors, colors that undoubtedly originated courtesy of some previous owner or, more likely, his or her child.  (Ah, the joys of buying used books on Amazon.)  Here's an example from the front matter featuring a wonderful quotation.

 (I grew to like this book even with its mites; the genial Darwin who graces its pages helps.  Further, there is sound science here, particularly in the annotations to the drawings.  There . . . I think that’s enough of a “review” to stay within copyright law and excuse my inclusion of the picture above in this posting.)

Fossil-like, my copy of The Sandwalk Adventures reflects its idiosyncratic history in its colors, though it tells the same story as its uncolored kin.

The Roads Traveled

As I made the annual trek to my summer cottage hidden far out on the north fork of Long Island, the tail of Whitman’s “fish-shape Paumanok,” I skirted (slowly) the southern edge of The City.  To the northwest, in “Mannahatta,” a tunnel-boring machine, deep underground, devoured Manhattan Schist, carving out massive tunnels for the newest line of the New York City subway system.  (Anna Kuchment, Underground Railroad: A Peek Inside New York City's Subway Line of the Future, Scientific American, July 13, 2011.)

The trinity of convoluted and folded bedrock formations beneath the Island of Manhattan – Manhattan Schist, Inwood Marble, and  Fordham Gneiss – rises and falls deep beneath the surface, dictating the peaks and valleys in the Manhattan skyline as skyscrapers seek stable bedrock.  To this amateur, the geologic history of Manhattan Island baffles.   The North American Tunneling:  2008 Proceedings (edited by Michael F. Roach) puts it nicely, "The geology of Manhattan is an open question" and proceeds to describe a complex interplay of rocks and forces.  Betsy McCully offers an accessible explanation on her website New York Nature.

The Manhattan Schist, a “blend of granite, mica, gneiss and garnet” as Kuchment describes it, perplexes the experts with apparently no agreement as to its age.  A billion years – back into the Precambrian – as McCully suggests?  Geologists Pamela and Patrick Brock think otherwise, positing that, “though its age and origin have been unclear,” it is an allochthon (a large block or sheet of rock moved a substantial distance by tectonic forces) formed approximately 570 million years ago, which would put it closer to the end of the Precambrian, in the Ediacaran Period.  (Bedrock Geology of New York City:  More Than 600 M.Y. of Geologic History, Field Guide for Long Island Geologists Field Trip, October 27, 2001.)  I find myself confused over the U.S. Geological Survey treatment of this rock.  Its online spatial data proffers a conservative estimate of the age of the Manhattan Formation that also highlights the uncertainty of it all.  The entry for “Geologic Age” for this formation is a definitive “Ordovician?”  (That would be 488 to 444 mya.)  The entire USGS spatial data description of the Formation seems composed mostly of question marks.  Yet, in a separate treatment of the geology of northern Manhattan Island, the USGS refers to the "Cambrian Manhattan Formation."

Regardless, this is very old rock and now, after being ground up to make way for commuters, it lives on, in a way.  A stream of trucks hauls away the crushed rock to city construction sites.  I don’t know if that’s a pleasing thought or not, this product of magnificent powerful forces being used for building up land or landscaping.  For some reason, I think of Rodney Dangerfield, “I don’t get no respect.”

Of course, this goes on all the time.  For better or worse (frequently the latter), we humans are equal opportunity users of the materials that surround us.  I love the buildings made of Indiana limestone that grace so many capital cities across the country.  To peer closely at these walls is to look back millions of years at massive numbers of fossilized remains (death on an incredible scale).  Curiously, I’ve never been upset about diatomaceous earth, that fossiliferous sedimentary rock, being used for, heaven forbid, kitty litter.

In contrast, I have hesitated over the generosity of the PotashCorp which trucks reject material from its Lee Creek Mine to dumpsites where the North Carolina Department of Transportation uses it to repair highways.  Now, that does seem an affront to the myriad Miocene fossil shark teeth, ray plate fragments, shells, and the like that abound in that material.  Not rarities but, to this amateur, treasures nonetheless.  The product of a few hours digging through a pile of Lee Creek reject material appears below.

Mining operations, construction crews, and highway departments can be great friends to geologists and paleontologists.  Lee Creek Mine is a premier example of a mining operation that has fueled paleontological research.  The rocks and fossils exposed at road cuts offer access to riches that otherwise lie sealed off beneath earth and forests.  The bulldozing at housing development sites tears off the top soil and, with luck, fossils see their first light in millions of years.  Sadly, it’s often a fleeting moving back of the curtain.

But one highway maintenance crew is now on my shit list.  The other day, I wandered down from my cottage to the road that runs along the nearby railroad tracks.  The summer ritual of reintroducing myself to wild flower friends was about to begin – if past years were any indication, at least 20 different species were waiting to be saluted.  Indeed, I had the thought of trying to do a full inventory of all the species present at different times during my stay.

Not to be.  The mowers from the county highway department had cut a murderous swath along the road the day before.

Well, a few bits of color survived.  Some low lying Chicory ducked under the blades and a couple of stalks of brave Yellow Goats-beard must have swayed at just the right moment.

Perhaps this citizen scientist will travel down this road monitoring the recovery of the flowers after their mass destruction.

Darwin's Marginalia

We have all seized the white perimeter as our own
and reached for a pen if only to show
we did not just laze in an armchair turning pages;
we pressed a thought into the wayside,
planted an impression along the verge.

~ From the poem Marginalia by Billy Collins

Marginalia – a word the poet Samuel Taylor Coleridge appropriated from the Latin early in the 19th century to describe those marks and comments written by readers in the margins, between lines of text, or wherever blank space appears in a book – offer a glimpse behind the curtain at great and not so great thinkers.  The Biodiversity Heritage Library is bringing Darwin’s marginalia to us in the fascinating Charles Darwin’s Library, a “virtual reconstruction of the surviving books owned by Charles Darwin.”  To the extent possible, BHL will be putting images online of each page of each of the books Darwin actually held in his library.  Darwin’s marginalia attracts intense scrutiny, less I think for their artistry, complexity, or acerbic quality, and more for whatever insight they may provide into the thought processes of the man and in the development of his theory.

Coleridge may well have been the high priest of marginalia which he created with such consummate skill that friends lent him books so he could fill them with his wit and criticism.  In a satirical essay extolling borrowers (“opening, trusting, generous”) and deprecating lenders (“lean and suspicious”), Charles Lamb celebrated the marginalia of his very close friend Coleridge:

Reader, if haply thou art blessed with a moderate collection [of books], be shy of showing it; or if they heart overfloweth to lend them, lend thy books; but let it be to such a one as S.T.C. – he will return them (generally anticipating the time appointed) with usury; enriched with annotations tripling their value. (The Two Races of Men in Essays of Elia, p. 48)

Beyond Coleridge and Darwin, there have been other stellar practitioners of the art of the marginal note, among them, Mark Twain, William Blake, and Herman Melville.  And then there are the rest of us, we pedestrian practitioners who took a crash course in creating marginalia when we hit college.  (Yes, highlighting counts.)  Indeed, we unknown annotators find ourselves included among the well-known as the subject of serious academic study.  In Marginalia:  Readers Writing in Books (2001), University of Toronto professor of English Heather J. Jackson argues that

Given the recent shift of attention from the writer to the reader and to the production, dissemination, and reception of texts, marginalia of all periods would appear to be potentially a goldmine for scholars.  (p. 5)

She adds, “And so they are, but they are a contested goldmine.”  After looking recently at the marginalia with which I decorated (desecrated?) my copy of Milton’s Paradise Lost, some contesting of the goldmine seems warranted.

The value of marginalia may stem from the privacy of their creation.  Edgar Allan Poe posited, “In marginalia, too, we talk only to ourselves; we therefore talk freshly – boldly – originally – with abandonnement – without conceit . . . .” (Marginalia, November 1844)  Marginalia of substance may speak volumes about the reading process.  Kevin J. Hayes nicely described a book of Herman Melville’s marginalia as offering “an excellent way to see how Melville read what he read.”  (The Cambridge Introduction to Herman Melville, 2007, p. 132)

With that last thought in mind, I have dipped into Charles Darwin’s Library on several occasions in pursuit of interesting marginalia.  It’s a mixed blessing for the casual visitor because, not unexpectedly, most of what one finds are vertical lines (scores) in the margins which Darwin used to mark specific pieces of text.  That which caught his attention may have great import for the Darwin scholar, but decidedly less so for the tourist.  Less frequently he was moved enough by what he read to elevate his marginalia to words, phrases, even sentences.  For me, these are where the fun resides.  I envision him sitting in his study at Down House, he has a pencil in hand and is reading intently.  (Drawing below is from The Century Illustrated Monthly Magazine, Volume 25 – Nov. 1882 to April 1883.)

Consider his marginalia in Colonel Charles Hamilton Smith’s Dogs (volume ten of the Naturalist’s Library, published in 1840).  Often, as he read Dogs, Darwin marked with pencil certain lines with a wobbly scoring and underlined others.  Sometimes, as he did on page 104, he scored lines in the left margin with a very curious slash and hump (a two-stroke marking or perhaps a single-stroke reverse check).  Consummate creators of marginalia have been known to resort to a shorthand to convey meaning through a quick glance long after the book is finished, or to avoid the tedious repetition of similar comments.  In his copy of Robert Southey’s Joan of Arc, “Coleridge came up with so many objections that he had to abbreviate them, as in ‘L.M.,’ for ‘ludicrous metaphor,’ and ‘N.,’ for ‘nonsense.’”  (Ian Frazier, Marginal, The New Yorker, June 28, 2010.)  Was the reverse check in the left margin such a code?

Frankly, I don’t know when Darwin read Dogs nor what he thought of the book’s overall value, though I suspect his review may not have been favorable.  On a few occasions while reading it, he did dash off a comment.  At a couple of junctures, Hamilton Smith apparently sufficiently tried his patience that Darwin allowed himself to inscribe a cutting remark.  On page 113, he fashioned his own footnote for a half dozen lines which he scored.  Next to the scoring, he scribbled an “a” in a bracket and then at the foot of the page he placed a corresponding “a” and bracket and wrote in legible but apparently hasty script,

a most unclear rigmarole of old names, all these latter pages

Later in the book, on page 162, when Hamilton Smith wrote about the breeding of greyhounds in Ancient Greece and elsewhere, Darwin marked the passage with two exclamation points and then dashed off,

How little he knows of Selection

 I’m certain there’s more to be gleaned from the marginalia in Dogs but it would require a heavy amount of study of a volume that Darwin may well have considered of limited value or worse.  Hamilton Smith actually does appear in On The Origin Of Species for a thesis about stripes in horses, though Darwin summarily dismisses it as “highly improbable.”

Darwin was capable of the truly cutting and dismissive comment.  The naturalist Louis Agassiz believed in the special creation of species, asserting that the geographical distribution of animals was a reflection of the “order of succession” in God’s plan of creation, that animals lived where they had been created.  With the publication of On The Origin Of Species, he became the primary American foe of Darwin’s theory of evolution.  (For more on Agassiz, see Louis Agassiz:  A Life in Science by Edward Lurie (1988))   But before Darwin published his masterpiece, Agassiz’s Contributions to the Natural History of the United States of North America (part 1 of volume 1) appeared, published in the United States in 1857.  In it, Agassiz wrote that the geographical distribution of animals “stands in direct relation to their relative standing in their respective classes, and to the order of succession in past geological ages, and more indirectly, also, to their embryonic growth.”  (p. 120-121).  To which Darwin commented succinctly in the margin

All rubbish

To my mind, one of the most amazing pieces of marginalia in Darwin’s library resides in the left margin of page 442 of volume 2 of Charles Lyell’s Principles of Geology, 5th edition, published in 1837.  Knowing when he wrote it would be fascinating, particularly because it would allow us to map it against what is known about Darwin's development of the theory of evolution.  An article in the Washington Post on BHL’s Charles Darwin’s Library brought it to my attention (Notes that Darwin Made in His Books Reveal How He was Thinking, Elizabeth Pennisi, June 28, 2011, online version of article at this link)

In the passage in question in Principles of Geology, Lyell recapitulated what he had written in the last several chapters regarding “the reality of species in nature.”  For his 4th “inference,” Lyell described an absolute limit on possible variation in individuals within a species.  To which Darwin added a revealing piece of marginalia, in a voice so fresh and alive,

if this were true adios theory