Messing with DNA — it's what we do

kw: book reviews, nonfiction, genetics, domestication, genetic engineering, sociology

DNA is practically designed to be tinkered with. It isn't hard to do. At age ten I was hybridizing tulips. I produced some pretty varieties. Then a master of DNA tinkering showed up: an infection by the Tobacco Mosaic Virus produced many "parrot" coloration varieties. Within a couple of years, things settled down, and some of the tulips went back to being the mostly solid-colored ones Mom had originally planted, plus a few of my 2- and 3-color hybrids, but some striped ones remained, apparently now breeding true to their new appearance.

Some time between 15,000 and 40,000 years ago, a subtler change occurred in an animal that hung around human encampments. Wolves had probably been stealing from garbage dumps for thousands of years already. Some, most likely younger ones, got used to continuing to gnaw on cast-off bones even if a human showed up, if the person didn't make threatening noises or moves. Did people domesticate wolves, did wolves domesticate themselves, or did both species domesticate each other? I suspect most humans were originally rather displeased about having scavengers around, so I favor the latter version. 

Whatever narrative appeals to you, at this remove of time, the main thing we know is that even very wolf-like dogs remain like juveniles. It's like dogs all have Peter Pan syndrome and never grow up. If you ever get acquainted with a wolf, as I have, you'll realize that an adult wolf is all business. Reach out a hand, and get back a stump. Make the kind of "hand-on-knees" play gesture that'll make almost any dog trot over to play tag, and a wolf will most likely fix you with a cold stare, "Seriously, human?" That's if it knows you well enough to stand there to watch your antics.

The critters we call "farm animals", "pets", and "livestock" are genetically very different from their ancestors. Cattle came from Aurochs, for example. On a camping trip I once awoke in the tent to find cattle grazing all around. I went out and swatted a few butts and said things like, "Get along now, my wife has to get up." They placidly moved on. Try that with Aurochs (you'd need a time machine), or even Bison. Your remains will soon be well mixed with mud.

Domestication and selective breeding are the traditional way to mess around with DNA. More recently we've gone from simple domestication to hyper-tinkering, still by cross-breeding and such. Your great-grandma's chicken weighed a pound and a half. Now a roasting chicken can weigh as much as eight pounds, and they cook twice as fast as a turkey of the same size, so when my wife and I have Thanksgiving alone (that may be what we have to do this year…will 2020 never go away?), we roast a chicken. But even fryers in the 3-4 pound range frequently have broken legs so frequently, because they have been bred to grow so fast their bones can't keep up.

Then there are all the plants we call "crops", plus "garden plants" and "house plants". Unless you go to the wilderness to get plants for your garden, everything in your environment has been genetically changed in the past centuries or longer. A long time ago I collected ferns for a large terrarium I made from a leaky fish tank. Forty years later I still have two or three of them. They are "wild", even thogh I keep them in "captivity". But the vegetables in one garden, and the lilies and irises and such in others, are far removed from their wild ancestors.

Dogs and domestic animals of all kinds are the backdrop to the opening chapters of Life Changing: How Humans are Altering Life on Earth by Helen Pilcher. The various kinds of selective breeding are just the start. Hybridization is another, like what I was doing with tulips, but more persistently and permanently. The mule is an ancient hybrid. Even though it is famously stubborn, it is stronger than a horse or donkey and eats less. It's the prototype of a sterile hybrid, which makes it a made-to-order animal that won't breed a herd of wild mules and take over a chunk of forest or field. Other hybrids are fertile and sometimes they settle down to become a new, stable species.

There are chapters that get into molecular engineering and genetic engineering, mainly the newest tool: CRISPR-Cas9. Humans didn't invent this tool, we discovered it. Microbes have been using it for a couple of billion years for their own purposes. It turns out that we can use it to cut-and-paste DNA however we like. Getting DNA from some cells and patching stuff in and out is pretty easy these days. The next step is harder. So hard, we're very early on the learning curve for putting the edited DNA into a working cell or a virus that can insert it into a living cell without horrible or fatal side effects. The next couple of decades ought to be interesting.

Methods more similar to the traditional interest me more. In vitro fertilization (IVF: test tube babies were the first human products, including some of my relatives) is one way to speed up the breeding process, or to cause it to happen when there are natural barriers to natural breeding (in humans, these are summed up as "infertility"). For example, IVF is being used to breed corals rapidly or to cross-breed them in an effort to produce varieties that can survive in the oceans as we expect them to be for the next couple of centuries.

That introduces another aspect of "altering life". The life we ignore, except when we go "enjoy nature" or do some "ecotouring", is being affected a lot more than we realize. Consider this: 96% of warm-blooded animals on Earth are domestic; 2/3 are birds and 1/3 are mammals. Most living birds are chickens, about 24 billion. We breed them so fast, though, that there is a total turnover about every six months because worldwide consumption of chickens is 50 billion. Cattle number about a billion. They breed more slowly; about 300 million are slaughtered for food yearly. They outweigh the chickens, probably about ten to one. Besides the space taken up by all the livestock, about half of all farmland grows crops to feed the chickens and cattle, plus swine, sheep, goats, turkeys, and so forth. The 4% of total animals that make up all the wildlife on earth have a much smaller Earth to host them.

It is heartening to read in the later chapters of efforts to "rewild" some places. The author highlights a few, such as the Knepp Estate in Sussex, England and Pleistocene Park in Siberia. Large and largish keystone species such as boars or elephants will, for free, "engineer" a landscape such that it is attractive to such a great variety of other plant and animal species, and the variety and beauty multiplies. Rare creatures (the Purple Emperor butterfly is a great example) are found at Knepp that are seldom seen elsewhere. Sturdy, Arctic-hardy horses are making Pleistocene Park better and better as a habitat for numerous small animals and the plants they favor. Mammoths, or cold-adapted Asian elephants if the Woolly Mammoth cannot be "re-evolved", would do much more to return that area to its earlier splendor.

It was such a pleasure reading this book that when the author put in a plug for her earlier book, I snapped up a copy. Stay tuned on that. In the meantime, this book is a lot more than a "gee whiz" compendium of things we can do with DNA. It emphasizes the hopeful trends that are arising. It points toward an Earth in which humans begin to play a little nicer, as we realize just how interdependent we are with "the rest of nature."

Applying a scalpel to a city

kw: book reviews, historical fiction, mysteries, plagues, folklore

New author K. Avard is a family friend. His sort-of-fiction-sort-of-nonfiction novel First, Do No Harm was released earlier this month. By his own account, he reads a great deal, possibly more than I did at his age. He spent more than a year in Austria and nearby countries, which clearly provided fodder for this book.

Background facts: 

• Vienna suffered a Great Plague in 1679, which was almost certainly bubonic plague. There is a monument to the event near city center.
• Vampires were considered very real around that time, and some historical events seemed to confirm their reality. This led to the impaling and burning of disinterred corpses that apparently had not "rotted enough".
• Alpen (plural of Alp, not related to the word for "mountain" but to "elf") were folkloric creatures similar to incubi, thought to sit on a sleeping person and suck either their breath or their blood. There is a sexual element to incubus stories that is absent in stories of the Alpen.
• Plague doctors who went to afflicted places and claimed to be able to cure the plague have been accused of spreading it as asymptomatic carriers.

I have not asked Mr. Avard of these things. They are matters of my own knowledge and research I did while reading the book. There may be another thread as well. In Bram Stoker's Dracula, a side narrative concerns an insane man in a mental hospital who worships the vampire at a distance. This man does things such as breed flies, feed them to spiders, and then eat the spiders, under the delusion that consuming so many lives, at first and second hand, will increase his own stock of "life stuff". This narrative was ignored in the various vampire movies and follow-on vampire books and films and TV dramas. But it may underlie a character in the book named Thomas, self-named Belial.

The protagonist Dietrich is a medical doctor who finds himself in the middle of a sudden onslaught of plague. He becomes the central player as he and several companions, including his formidable sister and a very compassionate bishop, must become detectives to determine whether the epidemic is an entirely natural phenomenon, or is there a supernatural element? Are Belial and the plague doctors partly angelic, as they claim, and thus doing God's work? Are they Alpen? If they are angels, are they angels loyal to Jehovah, or are they fallen angels loyal to God's enemy? The denouement provides only a partial answer to all these queries, which testifies to the author's skill and understanding of the ambiguities of real life.

If I go into more details of the plot, it could spoil the enjoyment of other readers. Some may be like me and enjoy comparing the narrative to the facts of history. Others may prefer to read it undistracted by such things. The book offers delights for both.

The absence of a colophon and some other indications show that the book was self-published. The author did speak to me of a distributor, so he apparently did nearly all the work himself but found it best to farm out the advertising and distribution. One result of self-publishing is the lack of a copy editor. I am a compulsive proof-reader, so I found a few items that I'll pass on to Mr. Avard, so he can brush up the text if he decides on a second printing. Most will escape notice by most readers. 

I would advise him and other self-publishers: Locate a friend who can read with care and clear up typos and solecisms, or hire a professional copy editor to give the text a run-through. The rather small number of items I found testify to the author's care, but also show that nobody's perfect. I read and copy-edit everything I write, and I sometimes find things I missed when I read again at a later date.

I hope author K. Avard continues writing, and offers lovers of mystery and historical fiction further delights in the future.

A narrow view of art

kw: musings, poetry, art

I work the puzzles in the daily newspaper, including a feature titled Cryptic Byword, compiled by Luis Campos. A few days ago the deciphered quote was this:

"The best poetry jolts and shocks; it mines language for what we have not seen, have not heard" —Canadian Poet Dionne Brand.

My first reaction was, "What a stupid statement! This 'poet' lacks imagination." Of course, I had to look her up. Ms Brand has impressive credentials, including a term as the Poet Laureate of Toronto (9/2009 - 11/2012). From the bits of her writing available on various web sites, I find she is indeed an very talented writer. She has also, as a past Professor of Women's Studies and now a Research Professor of Theater and English Studies, ensconced herself in a narrow academic setting in which perpetual outrage is encouraged and rewarded. She is doing great work in her chosen field, so I do not blame her for the view expressed above, though the adjective "polemic" should be inserted before "poetry".

Before looking up her vitae, I mused about poetry, and about art in general, and its purposes. I like poetry, but I don't obsess over it as some do. I have bought precious few of the multitude of poetic anthologies, and most of those I own were gifts. According to the accepted taxonomy, poems come in three species:

• Structured verse with meter and rhyme. For generations this was "poetry," whether the heroic couplets of so much English verse including Shakespeare's frequent rhymed couplets, the dactylic hexameter of Homer and classical Greek poetry in general, or the tight structures of the few subspecies of Sonnet. Even Limericks and Clerihews, which the "serious" literati might despise, have solid structures that require creativity.
• Blank verse. This is a specialty of playwrights of the Elizabethan theater. There is the metrical structure (variously violated, particularly by Shakespeare) of the ten-syllable iambic line, but with no rhyme scheme.
• Free verse. This is the prevailing genre of the Poetry Slam, where jolts and shocks abound. I look upon most free verse as prose with the lines broken in sundry places. Some free verse is very well written. Some.

Whichever species a poem belongs to, what functions does it perform? Must it shock? I have at hand Sonnets From the Portuguese by Elizabeth Barrett Browning. The turns of language may induce the occasional jolt, but such is not the poet's aim. She was expressing her emotions during her courtship with Robert Browning, before they married. A simple view is that her aim was to express Love. In a more nuanced view she was working through the cloud of feelings surrounding her growing love, first her doubt and fear and then affection and awe, and finally acceptance and comfort. They show her growth until, in the 43'd of the 44 sonnets, she could pen one of the most famous lines in English: "How do I love thee? Let me count the ways." She goes on to enumerate seven, with clear indications that she is just beginning, but has run out of "sonnet space"!

My all-time favorite books of poetry are When We Were Very Young and Now We Are Six by A.A. Milne. I have the 1956 editions, given me by my parents when I was about ten years old. Surprised? Although I love Frost and Dickinson and Stevenson (I have A Child's Garden of Verses), it is to Milne I most frequently turn…for what? For humor, for insight into the child within, and for their lovely sound! I read them aloud. Our son used to love it when I would recite "Disobedience", which begins

James James Morrison Morrison Weatherby George Dupree
Took great care of his mother, though he was only three.

Opening each line with a dispondee (two long, stressed syllables) is genius personified! The following anapestic feet, and variations on them, keep the poem galloping along. Although there is a shock when a reader realizes the boy's mother is not returning, the light tone of the poem indicates it is an object lesson, not a report of a tragedy. It is a poem of turning-the-tables.

A.A. Milne's children's poems remind me to smile, to slow down and smell the flowers. I have a rather dour personality, and therein I find balm for my soul.

While I prefer rhyming verse, I can be stirred by blank verse…but it has to be very good! There is nothing better than the inspiring speech from Henry V by Shakespeare known as "St. Crispin's Day", which brought "band of brothers" into the English vocabulary. This is poetry that both ennobles and motivates.

Do I have any favorites among the lengthy ranks of purveyors of free verse? Not a one. Having read a few poems by Professor Brand, I can admire her skill, but I am otherwise left cold. I have also partaken of portions by Tony Morrison; though she was not a poet, her prose has poetical power (I have read only portions, no complete novels, because they go places I don't wish to go), and is frequently polemical also. I can analyze a work and discern its polemical intent—and so far, everything of Brand's I have seen has polemical intent—but I am not motivated. Polemics are for motivating, but you have to hit the right buttons. Sorry, Ms Brand!

And what of the other arts? There are painters and sculptors who make it their business to jolt and shock, but they are generally inferior, if not in craft, then in vision. There is "art" that demeans, and I don't mean only pornography. In the performance arts in particular, a few modern comedians carry on the uplifting tradition of Jack Benny or Red Skelton, but they are few. Far more must be "blue" to be funny, although they elicit mostly snickers rather than honest laughter.

In my folk-singing-in-coffee-shops years, I was sometimes asked why I sang certain songs. I would reply that I wished to raise my audience up, not knock them down. Every artist, of any genre, has this choice: ennoble others, or debase them.

I would agree with the second half of the quote above, that poetry ought to "mine language". To what purpose? Here is my shorter proverb (and you can substitute "art" for "poetry"):

The best poetry helps the reader grow.

The Jurassic wasn't all dinosaurs

kw: book reviews, nonfiction, monographs, paleontology

After reading a monograph about paleontology in northern Egypt, published by the New Mexico Museum of Natural History and Science, I saw the museum has a series of monographs available freely as e-books. I followed up with their Bulletin 23, Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A., by John R. Foster. The contents of the monograph, published in 2003, form the major part of Dr. Foster's PhD dissertation.

This is not light reading for "escape", unless you are like me and can wade through the necessary details that are the stock in trade for scientific monographs. Paleontology is one of my loves, and who doesn't love dinosaurs? The Morrison Formation, composed of rock layers with ages from 155 to 148 million years, is the most famous dinosaur fossil source in the world. Thousands of dinosaur specimens have been recovered from a great many quarries around the Rocky Mountain region that includes portions of the states of Arizona, Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming.

I have a particular fondness for the Morrison Formation because it makes up one "ring" of exposures around the Black Hills, where I spent several years during graduate school. Although my study area required rock samples of the Precambrian rocks in the core of the Hills (granite, gneiss, graywacke, and schist, primarily), I hiked all over the area and enjoyed seeing the spectacular cliffs of Morrison mudstones and limestones.

After an Introduction, the author proceeds in standard form, beginning with Methods and closing with Results and Discussion, and Conclusions. The three chapters between these bookends describe the localities and quarries from which specimens were obtained, the species studied, and the ecological categories found in the various areas where the Formation crops out.

Boiling down the science-speak, I can share a few of many interesting matters. Firstly, the number of species of all sizes is impressive. While big dinosaurs get all the press, and had a combined biomass that totaled perhaps half of all animal biomass, smaller dinosaurs, lizards, turtles, frogs, salamanders, mammals of many kinds (all small), one snake specimen, and several kinds of fish were the components of a complex food web, or rather several food webs in environments ranging from semiarid to stream-and-lake areas.

The Camarasaurus and Allosaurus shown in the image above were the most common larger dinosaurs. However, the more familiar Brachiosaurus, at 44 tons, was much larger than the Camarasaurus, which weighed 14 tons (these are averages for large adults). A grown Allosaurus weighed around one ton. It is unlikely that an Allosaurus, or even a pack of them, could overcome a grown Camarasaurus, let alone one of the larger sauropods. Juveniles, when they could be separated from a herd, were more likely prey, as were smaller herbivores and smaller carnivores such as Velociraptor. This is a similar to the situation today with lions, that leave mature elephants alone, but will sometimes go after a young one. Lions prefer animals their size or smaller. A grown wildebeest (gnu) weighs about the same as a lioness.

Secondly, the variety of mammals was greater than I had considered before: 29 genera, frequently with more than one species represented, although the author studied them only at the genus level. The mammals were numerous but small. I had to learn some new terms to get a clear impression of the mammal ecology. For example, I was rather intrigued by the name Triconodont, which means "three-cone-tooth." The molars of modern carnivorous and omnivorous mammals (including humans) have either two or four cusps. These small carnivores (half the weight of a small house cat, maybe 1.5-2.5 pounds) had molars in one jaw with three cusps, such as the four on the left illustrated here, and a single cusp in the opposing jaw, which fit between the three, as seen in the three teeth on the right.

This reconstruction of Triconodon mordax, with neutral coloring (I had to hunt for something not fanciful and stripey; this is from Encyclopedia Britannica), shows an animal a little smaller than a common opossum. It probably had a similar diet, unless it ate no plant matter at all; opossums are omnivorous, but prefer meat whenever possible.

Rather than go on and on, I'll close here with the note that the author writes well, with a readable style that comes through the required stodginess of scientific monograph writing. This Bulletin is worth reading to learn about what was living all around the dinosaurs in their day.

Peashooter versus straw man

kw: book reviews, nonfiction, politics, governance, polemics

A relative who dearly wishes to turn me against President Trump sent me a book. He included a note that he hoped I would not find it "fake news." I promised to read it, and over a couple of weeks, alongside reading other books that are easier to stomach, I did read it, all of it. Luckily it is rather short.

Afterwards I recalled something I heard once, "The elephant labored and brought forth a mouse." I've used that line to describe the Mueller Report on the supposed collusion with Russia by Candidate Trump. Let's see if it applies to this book: The Fifth Risk by Michael Lewis.

The book has two prevailing themes. Firstly, it presents a dark picture of the "transition" from the Obama administration to the Trump administration in 2017. Secondly, it outlines as praiseworthy the lives of several people in various departments of the Federal bureaucracy. Before long I put this analogy to the pattern: art analysis. Perhaps you had a class in Art Appreciation in high school or junior college. It used to be a common "easy A" class for college freshmen who needed to keep their GPA above 2.0.

There are two ways to analyze a work of art, whether a painting by Renoir, a sculpture by Rodin, or a Shakespeare play or sonnet. One is to examine every bit in great detail, to understand the artist's technique, and the other is to look more broadly at the themes, to discern the artist's aim or goal. Taking the first method to an extreme, one might literally disassemble the work at a nearly atomic level. With this in mind, I liken The Fifth Risk to the result of looking at parts of a line drawing, a caricature, and picking off all the bits of black ink and gathering them into a little bowl; followed by snipping out some of the bits of white paper, untouched by the ink, and gathering them into another bowl. With the two bowls in front of him, the author then described them in "See how black these are!" and "See how white those are!" terms. The original drawing itself has been left a sliced-up mess in which no discernible pattern or image remains.

One reason the book took me extra time to read is that I checked into many of the claims the author makes. The first, that there wasn't much of a transition, and that its leader, Chris Christie of New Jersey, was fired along with several of his team, can be largely substantiated by public statements former Governor Christie made during interviews in 2017 and 2018. However, he clearly missed the point behind the firing. Candidate Trump had promised to "drain the swamp." The initial team was moving towards perpetuating it. President-Elect Trump had no intention to replace outgoing swamp creatures with more swamp creatures, so he left many of the bureaus to run themselves until he could get other matters out of the way. He has a long history of letting people who are doing a job "well enough to avoid jail" continue while he puts out fires elsewhere.

This is an important concept. He seems to agree with a statement attributed to General Norman Schwarzkopf: "People don't go to work every day intending to do a bad job." Let's put that together with one of my proverbs: "Does the Devil know he is evil?" Contrary to the public caricature of Donald Trump, he has great street smarts. He knows that most people do a good job regardless of the administration under which they work, but some people think they are doing a good job, even that they are doing God's will, when they do the Devil's work. James Comey and Robert Mueller are two such.

Let's look a little further. I checked into other claims the author makes. I'll just touch on one to show a principle. Pages 69-77 are devoted to discussing the Hanford nuclear site, where a lot of plutonium was made, and the cleanup that has been carried on for many years since the site was shut down. The author claims that President Trump has proposed cutting the budget for cleaning up the Hanford site. It didn't take me long to find an article at energy.gov by Dan Brouillette (look under Hanford Cleanup Process). Briefly, the Plutonium Finishing Plant building was demolished and a large amount of contaminated soil was moved away from the Columbia River to a safer location. These reduced ongoing costs. Budget cuts the President introduced were based on the projected reductions.

This is a typical case. For all the cases I could check the reason a decision was made was not mentioned by the book's author, or the item was based on hearsay and truly is Fake News. This is not collecting black ink from a line drawing. This is adding black ink where there was none. In the end, I find that most of the black chips in the bowl of black ink are similarly false.

Do I think that Donald Trump is some kind of saint? No, not at all. I was not a fan of his in 2016, but I voted for him because a shuddered at the horrendous thought of a Hilary Clinton presidency. It didn't take long for him to win my approval. The reasons are listed (sadly, with numerous typos) in the web site Promises Made, Promises Kept. A few months ago I downloaded the list and dropped it into a Word document (default settings: 11 pt Calibri). It fills most of seven pages.

The "portrait" with which Michael Lewis began was a caricature, and a poor one at that. How does he do describing the people he admires, the ones who did keep things running in spite of the President's "benign neglect" (my term; I am sure author Lewis would object)? Cutting through the tendency to hagiography, I find a pattern. They are all dedicated, all found themselves practically backing into a job in government service, all doing a good job with little direction, either before or after the "transition".

Let me ask this: Why do they all still have their jobs (those who have stayed)? If they are part of the swamp, why haven't they been targeted and in some way forced out. I think most of us know that you can't fire someone from a Civil Service job unless they commit a felony and are convicted. But it is quite possible to exile someone to a useless position and let boredom have its way with them. To answer: the majority of the Swamp Creatures are the uppermost management … the scum rises to the top.

And while I think of it, was there really some kind of purge of "climate change believers"? It seems there was indeed a list-making exercise, not of all who "believe" in climate change, but of those who cry "Wolf!" about it, when that's outside their bailiwick. I note that there are plenty of folks in place who still do so, and the President hasn't "purged" them.

Here are a few things that would have happened already if President Donald J. Trump were the kind of anti-science tyrant that his enemies claim:

• James Comey, James Clapper, John Brennan and Andrew McCabe would have been not only fired, but taken out and shot, all during the first few weeks after Trump took office.
• Robert Mueller would have been fired within the first month of his "investigation". Anybody objecting would have been jailed.
• Nancy Pelosi, Charles Schumer, Adam Schiff and Jerrold Nadler would have been jailed or shot, a year or two later.
• Barack Obama, both Clintons and Joseph Biden would be in prison as we speak, charged with treason.
• The Department of Energy (and a few others) would have been summarily disbanded.
• Thermonuclear bombs would have been used against Beijing, Tehran, and Pyongyang.

The fact that none of these things has happened should give Trump haters pause.

I looked into the bio of Michael Lewis and found that his prior books, including a best-seller or two, were about sports. "Cobbler, stick to thy Last." The Fifth Risk is barely 200 pages in length. It has a prologue and three chapters, but no index. As noted above, the research is thorough in a specialized way, but the result is sloppy and grossly misleading. Somehow, author Lewis thinks it hilarious to take a cheap shot at Brian Klippenstein, about his liking for sheep farming; the ugliest cheap shot I've ever seen in print. One would think his mother trained him better. He may be an expert in sports, but in politics and governance he is a dilettante. He isn't an elephant who brought forth a mouse, he is a weasel.

Footprints that are almost forever

kw: book reviews, monographs, nonfiction, science, paleontology, trace fossils

"Take nothing but pictures, leave nothing but footprints." This advice for visiting national parks and other sensitive areas is ironic in its assumption that footprints are ephemeral. They usually are, but not always. The big footprint in the middle of the picture below is more than 100 million years old.

My wife took this picture in 1994 when our son was six. We were on a family trip to Colorado and nearby states. While I attended a business conference the two of them did some sightseeing. Right at the center of the picture is a "Bronto Bulge", the footprint of a giant dinosaur. The reddish rocks are mudstones, and while the mud was soft the creatures' feet left deep impressions.

Our son has his hand on the layer the Brontosaur (or other sauropod) stepped in. Just above is a thin, gray layer of ash, and then more mudstone, which filled the footprints. There are several Bronto Bulges along this exposure. They are an example of trace fossils. They occur in a great many places.

Prehistoric Trackways National Monument was set up in 2009 on a bit over 8 square miles northwest of Las Cruces, New Mexico. Its purpose is to preserve the greatest assemblage of trace fossils in North America. The 48-page brochure Traces of a Permian Seacoast was published in 2011 by the New Mexico Museum of Natural History and Science to illustrate the riches of this unique area.

The brochure cover shows a trace fossil in the making; a Permian proto-lizard walking in mud, leaving tracks. On rare occasions (that occurred millions of times over millions of years), footprints and other traces of animal activity have been preserved, to be seen today.

I once thought of fossils as seashells or bones found embedded in rock. When I was a geology student I took a course in Invertebrate Paleontology, There I first learned that worms crawling on sand and mud or burrowing into it, or the scuttling of crabs and trilobites, leave marks on or under a surface that can become trace fossils.

There are many more invertebrates (every kind of animal without a backbone) than there are vertebrates, by a factor of millions. Thus, most trace fossils record the presence or passage of worms, crabs, clams, and so forth. But a small number (still many thousands) have the tracks of vertebrate animals such as lizards, frogs, and turtles.

This picture shows a common type of trace fossil: worm burrows. Any time you are at a place with soft sediment, and animals are crawling, walking, burrowing, or squirming around, take note of the trails they leave. If another layer of sediment is soon deposited on top, particularly if it is of a contrasting type, like sand over mud or vice versa, there is the potential that, long in the future, those tracks will be seen again as a trace fossil.

The brochure illustrates and describes a number of kinds of animal life recorded in their traces. This picture shows the "discovery slab". The footprints are not those of a dinosaur. The National Park is a Permian site. The Permian period preceded the "age of Dinosaurs" which began after 250 million years ago; the Permian period was from 299 to 251 million years ago. The Park's rocks are primarily aged about 280 million years.

Thus, the footprints seen at right are from a reptile that may be similar to the one on the brochure's cover, but more likely belong to a species of  "sailback lizard" such as Dimetrodon. The biggest tracks in this picture are from that animal, and their are tracks from a few smaller reptiles, plus worm or insect crawl marks. Since the area was discovered in 1987, many fossils of animals new to science, plus their footprints or other traces, have been found there.

Dimetrodon is such an iconic creature that models of them are frequently included in packs of toy dinosaur models. They are not dinosaurs. They were present between 292 and 270 million years ago. The first dinosaurs arose about 230 million years ago, 20 million years after the end of the Permian period.

The brochure whets my appetite for spending a few days there. I love the national parks, and I'd like to visit this one.