Tag Archives: Paleontology

Go Carl!

Mr. Buell makes the big time, talking (albeit briefly) about Manhattan mastodons to NPR’s science writer Robert Krulwich. A four-minute piece of audio is available at the top of the page.

That’s the second time in a couple weeks NPR has covered coevolution of plants and Pleistocene megafauna. I smell a fad. By summer, I expect an all-Osage-orange channel on basic cable.

When Carl Buell is credited as a co-author of a new book,

the thing to do is to go to the Amazon page of the book in question, find the Publisher’s Weekly review and read it:

[Donald R.] Prothero, a geologist at Occidental College (After the Dinosaurs), explains how rich the fossil record has become. His goal is two-fold. First, he wants to demonstrate the wide variety of transitional forms that have been found, many within the past 20 years. Second, he aims to discredit the creationist movement. I have tried to document how they routinely distort or deny the evidence, quote out of context, and do many other dishonest and unethical things—all in the name of pushing their crusade. He accomplishes both of his goals (though he can be repetitious regarding the creationists), and his descriptions of recent research, much of it his own, are compelling. Prothero explains that the Cambrian explosion of life forms was anything but an explosion, and presents the impressive transitional fossils between reptiles and birds, along with striking evidence for mammalian evolution, including the relationship among hominid groups. With good science and some specific rebuttals to creationist arguments, this book demonstrates the importance of paleontology to the study of evolution. 208 illus. (Nov.)

Emphasis added. 208 illustrations. Carl Buell. 29.95. That’s 14 cents per Buell. We’d be stupid not to buy it. [Carl corrects the struck-out material in comments. It actually works out to a dollar per Buell. And though I of course did not mean to slight Dr. Prothero by emphasizing Carl’s work, Carl — in typically generous fashion — corrects my slight anyway.]

There is no balance of nature

I go to the desert hoping the desert will wreak changes in me, which is more than one should ever ask of a landscape. I want the wind to peel me slowly, layer by layer and imperceptibly, until my unnecessary armor is stripped clean.

It never happens. Not that way.

I sit and wait for the change to come. I long for it. I imagine the change coming as slight and as easy as a snakeskin shed well, and anticipate the clearing of vision that comes from losing the old, used-up lenses. And I am disappointed, and restless, and then when the change comes it is less like the abrasion of thin layers and more like the cracking of a walnut. I blink hard at the new, intimidating glare.

The desert has been working on me the whole time. It is a matter of thresholds. At some point the pressure becomes too great. Running this morning, the fence lizards that lined my path saw me coming from some yards away, and yet they did not retreat stealthily, methodically. Instead they froze in place until the terror I instilled in them became too great. A trigger reached when the clomping of my clumsy feet became too much to bear, they exploded one by one into noisy flight.

This is the geometry of change in the natural world. Continuous change is uncommon, and where found it is usually part of a cycle, the increase by small increments of morning air temperature, the upward march of tides. The sun will set and the air cool, and the tides will recede, and even with those familiar examples the continuity of the change vanishes if you change the scale in which you examine them. Each tide cycle is thousands of crashing waves, each wave a torrent of turbulent collisions never to be exactly duplicated. Each degree of warming is a chaos of unpredictable breezes, air temperature rising not at all for minutes and then by jumps as a warm wind flutters over the landscape, and temperature itself a measure of the speed of random collisions of air molecules.

The San Andreas Fault slips at about an inch and a third each year across California, but some decades it moves hardly at all and then it jumps 30 feet in a second.

I am tempted sometimes to parochialize, to claim that living in the arid West with its lower biomass tonnage per acre promotes a more visceral awareness of the true nature of change. Humid environments seem more insulated against change. Growing up back East one is more tempted to believe in things such as the “Balance of Nature.” Even the ugliest scar on the land is soon cloaked by ailanthus trees. The non-botanist is tempted to take that as healing. The western landscape suffers visible change from cattle, from tire tracks, from campfires and rainstorms. Those agents of change work in the humid world as well, but their immediate effects are subtler and thus harder to discern.

The sheer fecundity of the world conceals its vulnerability to change.

Creationists seeking to argue against evolution often liken the evolution of complex organisms by natural selection to the building of a DC-10 by a hurricane blowing through a junkyard. Their conclusion? Since such an event is staggeringly unlikely, a special sentient hurricane must have built the plane deliberately. But grant a few quintillion junkyards and continuous hurricanes, and further grant the nuts and bolts and sheet metal the ability to make copies of themselves if they find themselves blown into configurations that cannot be easily blown apart by the next hurricane, and give this whole process a couple of billion years to ferment, and the evolution of machinery as complex as airplanes is almost certain. Though you might not get a DC-10, exactly.

(Come to think of it, that is how DC-10s made their appearance. Two monkeys, given 25 million years, produced not just the Shakespeare folios but every other word ever written in any language. They didn’t need typewriters to do so, but they invented them anyway. Of course they didn’t set out with that in mind.)

With a wet rock bathed in light and hospitable to the rise of complex, mutable life, it was near inevitable that complex networks of such organisms would arise, each organism trying to survive, new properties of the system emerging with each new level of complexity.

But we mistake this complexity for law.

A farmer razes a forest, plants a crop, plants another, grows old and dies. Ragweed grows up in the furrowed earth, and sumac, and silver maple. In a generation the land is forest again. We once watched that process and ascribed it to an imperative we thought the land possessed. The forest was called a climax community, as though the land had a sexual urge to grow wood. But with each razing and re-growth the character of that forest changes. It is a matter of chance what manner of tree grows in the new-bare earth, a stochastic result of which seeds first lay successful claim to the vacant territory. Sometimes no forest at all grows when the plowing ends.

Climax communities were so described because they appeared stable. The living world tends toward stability, it was thought. When there is a long enough gap between catastrophes, the land cycles through a number of unstable states and reaches a stable one. It is a stable state because it lasts longer than the unstable states. On Cima Dome this week I expect to kick a number of rocks down talus slopes, most of them unintentionally. Dislodged from its place, where it might have been content to rest for centuries, each kicked stone will touch the earth in a dozen spots, none of them sufficient to hold it, until it finds a ledge or an obstructing rock or shrub to halt its downward progress, and there it will stop, at least for a time. Would we then say that tumbling rocks seek out stable states on the hillside?

Stable states last longer. This is not an insight into the fractal geometry of the world: it is a tautology.

There is no balance of nature. Or if there is, it is the balance of a teetering rock on a pedestal stable enough to hold it for the moment.

The living earth renews itself after each disaster only in the sense that what survives the disaster may, with luck, bear progeny better suited to disastrous times. Odds are those progeny will not be to our liking. It is the weeds and plagues and pests, the irruptive big-litter breeders, that repopulate the disaster areas.

North America was once trampled by huge herds of huge animals. Mammoths and mastodons, bears the size of Ford Excursions, ground sloths and camels and horses, vultures with 17-foot wingspans. There are paleontologists who hold that most of these went extinct due to hunting pressure from humans, the ancestors of present-day Native Americans. (This is not a popular notion among some, including some present day Native Americans, who feel it smacks of blame. As for me, when considering that some people armed only with sharpened stones may have killed off the short-faced bears, I can summon no emotion other than reverent awe.)

Population biologists have calculated that human hunters need have killed only a very small percentage of the North American megafaunal population each year, a few baby mammoths here and a pesky short-faced bear there, to cause a devastating ecosystem collapse in short order. When the large animals died out, everything that depended on them for food, for seed dispersal or for habitat, to compete with their enemies and rivals… all those were pushed to the brink. And change almost certainly happened abruptly, with all seeming more or less well until it suddenly all fell apart.

There are a lot more of us now, with technology far more destructive than Clovis points. We plow much of the land and trawl most of the shallow sea. We change the atmosphere, the temperature, the color of sunlight. More and more of the produce of the earth is diverted to our mouths. The balancing rock may be large, its pedestal broad, we seeming but flies alighting on it, but there will be a time when that rock reaches a threshold and falls, and we may not see it coming.

And all of our environmentalist culture is predicated on the notion that change is continuous. The sustainability ethic that environmentalists endorse is based on the assumption that that rock, seeing itself growing too light on one side, will smile indulgently at us flies and shift its weight so that we might carry on in comfort.

River of fire, river of stone

Did they look up, fox-wolves drinking the sudden
warm water? Did they even have the time
to look up at the odd glow to the east,
a second hellish sunrise, red as fire
incinerating forests? Broadleaved oaks
and ash, the lurid-leaved persimmon trees
whose fruit fattened the horses, fed the short
faced bears, leaf litter of magnolia trees
ablaze at once? The sky would have been dark
for days, the eddied stratosphere pregnant
with dust, and thin plumes of it blowing west
against the usual ocean wind, the storm
of fire stoked by a scouring blast
across the plains. Did the Eucyons flee,
or drawn by terror-stricken, injured prey
would they have chased the fire along its edge
coyote-like? (The opportunist dog
as old as Hesperocyon, 40 million
years ago.) Guile doomed Eucyon’s whelps
to leg-hold traps, to tar pits, to the leash,
so as the peccaries, pronghorn, the sloths
and rabbits ran wild-eyed and westerly,
the fox-wolves might have headed toward the fire.
No matter. They were drinking. Did the banks
glow ruddy? Did the wretched stream run dry?
The earth had opened up, and lava bled
into the Miocene Sierran streams,
ran toward the Fresno Sea. Did they look up?
That old, steep-sided river canyon might
have taken a few moments to escape.
Fish would have been turning belly up
as river water warmed, the main stem blocked
and shrinking pools filled gills with caustic ash.
They may have been distracted. When the wall
of seething rock, molten and fast, came down
the river canyon, sandbar pools in steam
subliming at its front, air crackling and the screams
of animals unable to escape
to herald it, they may have stood, eyes wide
reflecting fatal red, transfixed, and then
even the water in their veins would burn.
Who knows? The red brim-filled the rill,
burned every tree, each fish, each sprig of moss
and raptor’s nest, melted the top few feet
of gold-flaked cobble, scoured the soft rock walls
the river had incised, flowed swift until
the earth’s anger subsided, cooled, a strange
traumatic calm descended slow after
burn-out, and other fox-wolves came to eat
what meat there was, charred by the pallid fire
of trees, cool by comparison, and the new rock’s
red glow subsided over days. Rain came
and then the river, ousted from its bed
worked on the softer rock. Eucyon whelped
the wolves. The sloths died off. The salmon lost
its fangs. The land grew cold and mountainous,
ice shrouded the peaks, and fed the streams
to quarry out the rock. That river now
a long mountain, the lava all that still
remains of those old days, the canyon walls
long gone, the sea the river fed now plowed
for cotton, its flow frozen fine-grained rock,
wild oat awns nodding from its crevices,
and travelers intent on granite domes
pass by the mountain, never seeing it.

Xeric Conifer Woodland, then and now

Caution: do not anthropomorphize

MB said something about Joshua trees and junipers in the same field of view a few days back, and I promised a post. It’s not actually all that uncommon to see the two species growing together, as the lower altitudinal limit for junipers in the Mojave is just about where the upper elevational limit of Joshua trees lies, with some overlap due to local microclimates and such. Sometimes a fault will run through the bedrock and provide a path for groundwater to approach the surface, and junipers — which in the Mojave are generally kept from growing lower than around 6,000 feet due to drought stress — will thrive a bit lower, their roots stuck in the water table. If you climb the Sierra Club trail up Teutonia Peak on Cima Dome and look back to the east from which you came, you’ll see a straight line of old junipers stretching a mile back to Sunrise Rock. They grow at just above 5,000 feet, and though they set abundant seed each year there are no other junipers nearby. You have to climb a few hundred feet up Teutonia to find junipers growing off the fault line. On the plain between Teutonia and Kessler peaks, the junipers form a line of perforation running through the thick Joshua trees, the only real source of shade in the forest.

Go to one of the junipers, look around for a while — mind the cholla stems — and you will likely find nearby a low mound of twigs and Joshua tree leaves and cactus skeletons, sometimes two feet high by five wide. This is the home of the desert woodrat, a.k.a the desert packrat, a.k.a. Neotoma lepida. Packrats are ubiquitous in the Joshua tree forest, and the wealth of berries a juniper provides each year prove a powerful inducement to settle nearby. The rats, which are the smallest of their genus at about eight inches from nose to tail tip, are mainly nocturnal: they come out of their nests — “middens” — at night and forage for plants to eat. On Cima Dome they seem especially fond of Joshua tree leaves. Or maybe that’s just what’s there. As you walk you’ll see trees where each leaf on one side of a particular branch has been sheared off evenly — nay, meticulously and methodically, as if the branch were a cob of corn being eaten by an ex-Navy man at a Fourth of July barbecue. This is the work of Neotoma lepida, and if you look around you will find a packrat midden within 50 feet: if not a pile of debris out in the open, then a comfy sheltered midden wedged between rocks or under overhangs, which is the setup the rats actually prefer.

Thus, two important facts about Neotoma lepida: they collect plant material and their range is about a hundred feet in diameter. Add to those two facts a third: a midden, once built, may house many generations of packrats. Many generations. Hundreds. Thousands. There’s a Pleistocene-era midden in the Colorado Rockies that was used more or less continuously from 950,000 years ago to 800,000 years ago: 150,000 years of habitation, a pile of sticks and leaves with a history compared to which the cathedral at Chartres is essentially a Quonset hut, Stonehenge a tilt-up strip mall. That, my friends, is tenancy.

Middens that are out in the open suffer the depredations of rain and snow, gales and determined badgers. The rock-fortified middens are more secure. Over the years the rats will bring in leaves and twigs, fruits and shiny stones and car keys, and then new layers of material will be brought in to put atop the old, and as the woodrats carry out their daily affairs in the midden they will urinate over it all over a period of years. Woodrat kidneys are desert kidneys, rather efficient at excreting salts without too much water to carry them, and the salty mess congeals into a hard, ochrous resin.

That resin — charmingly called “amberrat” by packratmiddenographers — preserves the plant material. In a cave, or under a nice big sheltering rock, away from the elements, the amberrat can preserve the material for thousands of years.

Thus an old packrat midden is a record of the vegetation of the immediate area over the span of time in which the midden has been used. And where you have thousands of years’ worth of well-preserved plant material collected from a precise location, there you have paleontologists. (Where the material is preserved by stanky rat piss, there you also have graduate students whose job it is to clean the stuff.) The plant material is identified and dated, and then we have a bit of a picture of how the vegetation in the area changed, if at all, over thousands of years. (Given the rats’ proclivity for collecting small pieces of bone, the middens occasionally provide a glimpse into animal life as well.)

And since packrats are thick on the ground in the southwest deserts, our recapture of information contaned in packrat middens is limited primarily by the supply of graduate students. There are lots and lots of data out there. And in the Mojave, one of the things those data tell us is this: the altitudinal ranges of both Joshua trees and junipers were once very different than they are today.

17,000 years ago the desert didn’t just smell like rain, it often felt like rain. Where there are now playas and salinas at the bottoms of Mojave valleys, there were broad freshwater lakes rich in wildlife. It was a wetter time, and though the countryside was not particularly lush, there was enough water in the soil that junipers could grow far down-slope. So could Joshua trees, for that matter, and even single-needle pines. In a number of places throughout the desert, the valley floors — when not flooded — were covered in what is sometimes called a Xeric Conifer Woodland, what modern-day desert rats of the two-legged variety call “P-J,” or Piñon-Juniper Woodland. Joshua trees were a minor component of that forest.

And then the dry came. Around 16,000 years ago the drought started, and it really got underway about 10-12,000 years ago. The lakes dried up, even the deepest one in the Mojave, Lake Manly, leaving its bed in Death Valley dry and crackling in the heat except for sometimes. The valley floors got too dry and hot for PJ with scattered Joshua trees. The first creosote bushes started to sprout on valley floors, and some of those plants are still alive. With their fruit dispersed by any number of birds and mammals, piñon and juniper gained a foothold in the (relatively) wetter mountains. Joshua tree didn’t rise quite as far. But deprived of competition with their former conifer neighbors, the Joshuas now dominate their part of the Mojave — at least visually.

In the Antelope Valley, 60 miles from the ocean, downstream from the well-watered San Gabriels and Tehachapis, the valley floor still hosts mixed forests of Joshua trees and junipers. Or at least it does in those few square miles, like in the photo above, not cleared for development. Flickers still cut their arcing paths between the trees, and woodrats collect sardine can keys and pull tabs to perplex the graduate students of 14007 AD.

Understanding

Thanks, all, for answering the poll below. I wanted to double-check my assumptions before weighing in on the latest discussion making the rounds of science blogs, to wit: whether scientists should think about framing in discussing science with the public. For those of you not up to speed on the discussion, I’ll just say that there is disagreement over whether framing is lying or spin, or whether it’s just something people do anyway and one might as well be conscious of it. Bora has, I think, the best summary of people’s positions on the topic that I’ve seen, and some cogent thoughts of his own as well, some of which I think I agree with.

I do think framing science in mass writing is important, and on alternate days I think framing science is inevitable even when writing for an audience of scientists. When my writing here really works, I think, it’s because I’ve stumbled upon (what I will here call once and never again) a frame that compels attention, that brings the reader a new perspective on a topic. My success rate is subjectively determined, but I think I’ve hit the mark once or twice. I’m sympathetic to those who’d rather simply present their results in flat, straightforward form, but I have never once seen a scientific paper that did not in some way use metaphor or simile — frames — to get the point of the paper across to readers. Take a recent abstract of a notable article in Nature, which article we will revisit later in the post:

Did the end-Cretaceous mass extinction event, by eliminating non-avian dinosaurs and most of the existing fauna, trigger the evolutionary radiation of present-day mammals?

Where are the metaphors? There’s the “radiation of mammals,” an explicit reference to the way a phylogenetic schematic of a diversely branching clade looks. There’s an extinction that may have “triggered” that radiation. There’s the peculiar inversion of causality implied in the notion that the end-Cretaceous mass extinction event “eliminated” dinosaurs et al, when in actuality the extinction event and the dying out of the dinosaurs and ammonites and such are one and the same. There’s no escaping portrayal by metaphor, really.

But despite my I suppose postmodernist take on objectivity and its inaccessibility to the likes of us humans, I must confess to an extreme impatience with an undercurrent I see running through the defenses of conscious framing of science. There is an assumption regarding the inherent nature of that exchange that I find troubling, if not downright insulting. I metaframe that offensive frame below in graphic form:

framing science

The best, most neutral, least inflammatory, and yet still wholly disheartening summation of that undercurrent is this explicit statement by Matt Nisbet in a list of social uses of frames:

Average citizens use frames as schematic short cuts. Frames allow citizens to make up their minds about a topic with little or no other information, and to talk about their opinions with others.

I will say I don’t have an issue with that as a description of what is. But as a prescription for what ought, rightly, to be? Elitism, pure and simple.

Carl Zimmer had the best response to that sentiment, it seems to me:

[F]raming doesn’t seem like quite the right response to the fact that over two-thirds of people in this country don’t know enough about science to understand a newspaper story on a scientific subject. It seems more like surrender to me. Fixing high school science education seems a better plan. Don’t let kids come out of high school without knowing that a laser emits light, not sound; without knowing about standard deviations; without knowing what a stem cell is. Fixing high school science would be a lot harder than staying on message, but it would be a lot more important.

According to my statistically non-significant poll, a quarter of CRN readers claim to read science blogs occasionally despite science not being a main life interest. More than half read at least a few science blogs regularly. It’s a mistake to read too much, or maybe even anything, into that poll, especially given the venue, which if anything has spent the last four years collecting people tolerant of the author’s diverse and shifting attention. But a divide between a lethargic, ignorant public and an elite corps of pure scientists, it seems to me, would likely be expressed in fatter tails on that bell curve. I think this topic is worthy of further study and the NAS and NEA are thus each cordially invited to fund my important cross-disciplinary research, checks to be made out to the Consortium for the Advancement of Science Heuristics, which is a pretty long name so just put the acronym in the payable to line. Thanks in advance.

It’s a bit ironic. I decided today I’d better write something about this once I meet my paid writing deadline on Wednesday, then went off to get this week’s hay fever shots. They make me wait after, as I have mentioned, and I used the opportunity to catch up on the reading that had piled up while I spent February and March hiding under my blanket. I had missed, for instance, the fact that Jennifer had snagged a spot in the Valentine’s Day edition of Nature, which is cause for unbridled admiration and a little envy. And I read that piece, and then I turned to the above-mentioned Mammals in the Cretaceous article, the gist of which is that mammals seem to have diversified abundantly tens of millions of years before dinos went missing. There was a graphic in the article which I’d seen on people’s blogs:

Mammal phylogeny

I took a good look at the graphic in print, with reading glasses, sitting there in the allergy clinic waiting room, and suddenly the floor fell out from under me and I was doing my best to stifle sobs, and failing.

It’s a phylogeny chart, a graphic representation of the relationships among existing families of mammals, drawn roughly to scale in the time dimension to give an indication when different groups of mammals diverged from one another. The time line begins at the center of the circle, and along any path the closer you get to the perimeter the closer you get to the present day. The meat of the article is expressed in that dotted black circle, the end-Cretaceous mass extinction. Most of the branching that represents the evolved diversity among mammal families took place after that event, but a surprising amount of that diversification took place in the shadow of the dinosaurs, a cool enough conclusion in any event. The chart is color coded to represent the five major mammalian clades as described in the article: monotremes, marsupials, Afrotherians, Xenarthrans, Laurasiatherians, and Euarchontoglires. Primates are Euarchontoglires, as are rodents and rabbits, and a couple small families closely related to but not primates: the tree shrews and flying lemurs. Marsupials seem to have diversified after primates, an interesting blow to an old preconception of marsupials as somehow far more primitive than placental mammals, let alone our own vaunted order. Tarsiers and monkeys split before possums and kangaroos did.

There are lots of little tidbits like that in the chart, and I was finding them and enjoying myself, and then I noticed that Euarchontoglires and Laurasiatherians diverged about 100 million years ago. About 100 million years ago there was a population of weird little mammals, and some of them went off to become the ancestors of the Euarchontoglires, and others to become the ancestors of the Laurasiatherians.

I am, as implied above, a Euarchontoglire.

Zeke was a Laurasiatherian.

I looked at the point on that chart where the green Laurasiatherian branches and the red Euarchontoglire branches shared a common root, a hundred million years ago, and tears welled up. A hundred million years ago we diverged, our family riven, and an impossible length of time afterward we met, our lines scourged by a half-dozen mass extinctions and the good times between them none too pleasant at that. It is ridiculous to think of it as a reunion: I may as well weep to be reunited with my distant cousin the grass pollen making my eyes water, lost lo these billions of years. It’s a stretch, in fact, to think in terms of families. The chart describes populations, not individuals. The two clades may have diverged a million years after my common ancestor with Zeke perished.

I am but an untutored yokel and the complexities, the obligatory qualifiers are no doubt lost on one like me, without a Learn’d Scientist there to explain to me how I am wrong.

But a frame is a frame, and I wept in the fucking allergy clinic waiting room looking at lines on a phylogenetic map for a beloved cousin found and then lost again.

Zeke

February here is a time of reminders, of bright creased-red flowers swelling from dank wood, green renewed and moist, succulent. Downhill is a patch of Narcissus and he always stepped on them. Each year I would forget and lose myself in thought and then look up to see him trampling down the bright green stems, the leash still slack between us. My neighbors are patient people, and never complained though I saw it in their eyes. Their patience has been rewarded. The Narcissus are blooming this week, grown tall and unbent.

There is one patch of soil ungreened on the entire hill, a rectangle of upturned earth three feet by four. We went to the nursery a week after he died, bought blue flowers to plant over him. In our yard in Richmond he loved the Scilla: he would loll about for hours among the Delft-blue blooms, a wide patch of them two feet high until he rolled on them. I always meant to grab the camera. The nursery had no Scilla, but it is far too late for planting Scilla. We bought forget-me-nots.

I have been remembering a day eleven years ago, a mile down the road from my father’s house in New York, when we walked down Buffalo Creek in search of fossils. The creek was broad and nowhere more than a foot deep, sun-warmed July water slick with ropes of algae. We found a slab of shale, oddly intact and harder than its surrounding rock, with crinoids and brachiopods, horn corals in it, and I lugged it back a quarter mile to the truck. Craig and Allison were there with Becky, Zeke and me; we waded back upstream and then Zeke trapped himself on a little island, paced back and forth along the shore as we climbed the bank on the far side. He cried, grew a little frantic. It was only fifteen feet or so across, and no more than a few inches deep, a riffle really over shallow stones, and I called encouragement to him from atop the old abandoned bridge on which we’d parked. He didn’t listen. Before I could go back down to help him cross he’d run the other way across five times as much water, and up the far bank to reach the bridge from the other side. He flew up to us smiling. A cloudburst off Lake Erie hit and drenched us all before we could get in the truck.

The sun shone the day after he died, and we dragged ourselves out in it. South of us is the Heart Place, a ridge cloaked in pines, a reservoir atop it, and both of us went there alone with Zeke. Becky took him there when I was callous, and he’d drowse in the thick pine needles as she wept. I took him there when she was gone. We sat there together the day after he died, the trail up to the ridgetop a teary blur, our howls thrown at the unfair world below us.

It rained the whole next week.

Rain a bit on our dry soil and the soil comes up alive and green. Plums blossom all at once in February on the Pacific Coast, the quince and currants with them. There is a pink currant in our garden, and a yellow one, and both show color now. The creek is up. Mallards delve beneath submerged grass stems. I have been to the creek at least twice a day since we buried him, and I have not seen the egret flying once. Instead, he stalks the creek on foot.

I stalk the creek on foot. I run down to the bay and along the shore, race the trains rolling slow past the crew resetting sidetrack ties. Each morning I leave, walk stupidly to the closet door for the leash until I remember, go downhill beset by ghosts. At this corner I lifted him over the curb his last few weeks, when his feet were too unsure to land safely without help on the slanted pavement below. My right arm around his waist, my left hand under his breastbone I would lift him over, and steady him for a moment when his feet touched asphalt. At that long patch of ivy under oaks he would stop, smell the leaves that overhung the curb. His last visit to the park we lingered beneath that plane tree. He was stretched out on the lawn and I sat leaning up against the trunk, telling myself I would bring a book next time. On the way back up the hill he would stop again at that patch of ivy, look imploringly at me until I hoisted him, and he would lean against my shoulder for the next two steep blocks.

I turn the key in the lock and I hear him jump up to greet me and he is not there. I walk into his room and from the corner of my eye I see him lift his head from his bed to look at me through clouded eyes and he is not there. Until a week ago the sparrows foraged between his feet, trusting and unafraid. They pick over seeds and ants on the upturned soil now, and an Anna’s hummingbird browses the rosemary flowers next to him, its red head patch now dull, now brilliant through the breath-fogged window.

The plums will bloom, and then the cherries, and then the Bradford pears. When the crape myrtle blooms this summer we will travel, we tell ourselves. We will hike together unburdened by our love for him. The oaks will flower, and the grasses. The hills will brown. The wind will shift from the east. In October, or not long after, I will look up and notice rain. I will remember congratulating him, by that patch of ivy, for making it to one more season of rain, and not long after the plums will bloom again. The memory will fade and soften. I will forget him an atom at a time.

That day in New York I breathed hard putting the slab of Devonian shale in the cab of the truck, in the hollow behind the driver’s seat, and laid his blanket over it. He would sleep on it as we drove west the next two weeks, step around it for eleven years after that. He grinned in the downpour as Becky loaded him in the truck bed, climbed in after him with our niece. He was always so afraid we’d go on without him. The slab is twenty feet from him now, a jumble of Devonian crinoid stems and modern California dust. We found brachiopods that day, hard dull gems of the detail of life preserved. They shaped the rock around them. Years of proximity welded sediment into rock, a perfect imprint of the animal, and then the animal dissolved away into the world and left a void in its exact shape. The fossils we held were that void filled, a bit of dust at a time and pressed into the creases, a representation of the lost one finely detailed but still without life.

There will be years and years, each small forgetting a betrayal, each small betrayal a comfort, each small comfort another death. There is no lesson here, no lesson. Narcissus sought himself reflected in the world and found only death. Plums will bloom until there are no more plums. I will join him diffused into the soil, our component atoms intermingled one day soon, a dog and a man who walked together for a time, a brief spark of sweetness in an aching world.

And so like

Carl and I are all like emailing each other about the Pleistocene banner this morning, and he’s all:

What a shame about the teratorns.  If only they could have made it through the past few thousand years, they would have found a niche created expressly for them in the American highway system.  On my drive to the store this morning I passed enough small carcasses to keep a half dozen of the big guys fed for a week. I can see the “TERATORN LANDING ZONE -next 10 miles” signs along Rts 80 and 395 now.

You know? And then so like I go

Road sign

About the banner graphic

Hi, I’m Chris, and I’ll be your guide on this tour of the marvelous Rancholabrean Pinole Creek scene in the banner painting, brought to us by the fantabulous time machine of the wonderful Carl Buell. Please keep your arms and heads inside the blog as we get going. Thank you.

Continue reading

Biplanes of the Mesozoic

Kat sends along this very cool BBC story:

An initial assessment of Microraptor fossils from China suggested the animal spread its legs out laterally and maintained its wings in a tandem pattern, in a similar manner to dragonflies.

Now, researchers Sankar Chatterjee and R Jack Templin offer an alternative hypothesis.

Their evaluations of the limb joints and feather orientation indicate that a tandem wing design would neither have achieved suitable lift, nor enabled Microraptor to walk on the ground easily.

Instead, the scientists report that its hind legs were positioned below the body, in a bi-plane fashion.

Every time I think I’m as impressed with biotic diversity as I can be, life comes along and whomps me upside the head.

 

Timeline

Time expressed in years before present day.

~2,000,000,000: Paleoproterozoic era, possibly during the Orosirian Period. Sediments are laid down in a shallow sea teeming with the newly evolved Cyanophyta, or blue-green algae.

~1,700,000,000: Probably during the Stratherian period, after the evolution of multicellular life, intense heat and pressure cook the above sediments into metamorphic rock, the Vishnu Schist. Intrusions of volcanic rock, the Zoroaster Granite, occur at about this time.

~1,200,000,000: During the Stenian period, as the supercontinent Rodinia is assembling, a layer of dolomite sediments out atop the Vishnu schist and Zoroaster granite. This will be called the Bass Limestone. After a relatively brief period of time, perhaps only a few million years, the sea from which the Bass Limestone was deposited recedes, and river deltas along the advancing shore lay down mud, silt, and sand that will become the Hakatai shale. These wetlands are home to stromatolites, large reef-like structures made by colonial cyanobacteria. The Hakatai emerges above sea level, is eroded away in part along with any overlying layers, and then re-submerged, after which sands are deposited —these will become the Shinumo Quartzite — and then tidal flat sediments upon the sands, which become the Dox Formation.

~1,100,000,000: A series of volcanic eruptions cover the area in basalt up to 1,000 feet thick. This will be called the Cardenas Basalt.

~1,050,000,000: After the Cardenas Basalt (and the rocks below it) is uplifted and eroded, shallow marine sand accumulates in some places: the Nankoweap Formation.

~1,000,000,000: For the next 175 million years, the sea advances and retreats. As it does so, it lays down alternating layers of coarse (delta or near-shore) sediments, and finer (deeper-water) sediments. These become, in order of decreasing age, the Galeros, Kwagunt, and Sixtymile formations.

~800,000,000: Tectonic faulting activity breaks up the landscape, creating fault-block mountain ranges and tilting all the strata from the Bass Limestone to the Sixtymile Formation to about 15 degrees from the horizontal. A hundred million years or more of erosion commences, in most places removing all trace of the Nankoweap through Sixtymile formations, in some places scraping the earth clean down to the Vishnu Schist.

~550,000,000: The region is once again slowly submerged in ocean water. This ocean water now has multicellular animals living in it, some of them, such as trilobites, brachiopods, and crinoids, with hard shells. As the shore advances over the landscape the Tapeats Sandstone is laid down, consisting of coarse beach sand and conglomerated cobbles.

~530,000,000: Shallow seas deposit silt, which will become the Bright Angel Shale.

~516,000,000: The sea is deeper now, and deep-water calcium carbonate precipitate accumulates on the sea floor, which will fuse into the Muav Limestone. For more than 150 million years afterward, any sediment laid down on top of the Muav Limestone will be eroded away — if any is in fact laid down, which we do not know.

~350,000,000: Water erodes channels in the top of the Muav Limestone, and this water is rich in calcium, likely from dissolving the Muav. Some of that calcium is left behind as precipitate. It forms the Temple Butte Limestone.

~330,000,000: The area is now near the equator. A shallow tropical sea teeming with Devonian animals and aquatic plants covers the land. Thick layers of limestone and dolomite are deposited on the floor of this sea, entombing and fossilizing many of its inhabitants. This will become the Redwall Formation.

~325,000,000: Tidal estuaries deposit mud and silt, which becomes the Surprise Canyon Shale. This rock is friable, and all but a very small amount of it is eroded away over the next fifty million years.

~285,000,000: Shallow estuaries and tidal flats cover the land. The sediments laid down in them become shales, siltstones, and limestones. Some of the layers — collectively known as the Supai Group — contain fossils of early amphibians and reptiles.

~265,000,000: After another dry period in which rock layers are eroded, the water returns: riparian wetlands in a generally arid climate deposit a torte of mud, silt, and rust in many thin layers. This will become the Hermit Shale.

~260,000,000: Chronic drought hits the area, and the landscape becomes a desert of pure quartz sand, which becomes the 600-foot-thick Coconino Sandstone.

~251,700,000: In an event perhaps related to the chronic drought, almost all life on Earth dies.

~250,000,000: Surprise! The sea comes back, comparatively devoid of living things. As it advances and recedes, occasionally leaving behind chemical-rich lagoons of water to dry out and leave their dissolved salts behind, layers of sand and calcinated silt and gypsum are deposited atop the Coconino sands to become the Toroweap Formation. Starting at about this time, braided coastal rivers deposit thick layers of silt and sand, the Moenkopi Formation, all of which will then be eroded away — at least in the area we’re discussing.

~225,000,000: Another sea, or series of seas. These deposit calcium carbonate, which will become the Kaibab Limestone, some of the youngest rock in the area. But not the very youngest.

~75,000,000: After being walked all over by dinosaurs for 155 million years, the land begins to rise up. It is the start of the Laramide Orogeny, which may or may not have anything to do with the Farallon Plate subducting under the North American Plate at the latter plate’s western edge, which is now along North America’s west coast, in Utah. For whatever reason, the whole countryside starts to lift up into the air.

~35,000,000: Another pulse of uplift. Watercourses in the area respond by digging deeper.

~5,300,000: Geologists will disagree in the early 21st century as to what happens now. Some will say that the Hualapai drainage system, digging ever deeper and eastward into the Kaibab Plateau, breaks through into the drainage system of the Ancestral Colorado, which until now had flowed southeastward into a lake basin. The opening up of the Gulf of California by the San Andreas Fault likely plays a role, as the Hualapai had also formerly drained into a lake basin. The lowering of the watershed’s bottom end to sea level greatly increases the cutting power of the river. Other geologists will maintain that stream capture alone could not produce the landscape of the 21st Century, and that the lake the Ancestral Colorado fed probably overflows into the Hualapai’s drainage. Either way, a catastrophic flood takes place, and the carving of the Grand Canyon begins in earnest.

~3,000,000: The climate gets wetter during the Pleistocene, and more water cuts the Canyon more deeply.

~1,800,000: Volcanoes erupt, forming the youngest rock in the Grand Canyon. The eruptions dam the river at least a dozen times over the next 1.4 million years, causing gigantic reservoirs to form. Some of the lava dams are 1,000 feet high, with the full force of the Colorado flowing over them in impossibly huge waterfalls as it cuts troughs through them. The Canyon reaches nearly its current depth about now.

~10,500: There are definitely people passing through here by now. How long they’ve been doing so we don’t know.

~4,000: There are definitely people living here year ‘round by now.

~1,200: The Ancestral Puebloan people build remarkable and sturdy edifices in the area.

138: John Wesley Powell rafts the Colorado through the Canyon singlehanded.

113: Much land around the Grand Canyon is declared a preserve by President Benjamin Harrison.

99: Grand Canyon National Monument is established by Theodore Roosevelt.

88: Grand Canyon National Park is signed into existence by Woodrow Wilson.

40: My friend Dave prevents the building of two dams within the Canyon.

6: President George W. Bush, an avowed fundamentalist Christian and smirking denier of scientific fact, is sworn into office.

3: The National Park Service approves the gift-shop sale of a book claiming the Canyon is just 6,010 years old while denying other new books shelf space. Park Service brass stonewalls in defense of the decision, despite sharp criticism from the non-ignorant community, until the present day.

2: I trace the delicate outline of a crinoid stem in a block of Redwall Limestone that has fallen a few hundred feet from its place of origin, far above the trail. It exists, for now, until the wind and water break it and it runs out to the fetid water of Lake Mead to add its silt to the reservoir. A million of its compatriots are still encased in the rock above. I look for the mold, the negative impression of the stem where the rock has split, and find it. The texture of the living crinoid is pressed into the rock, a Devonian cuneiform, and a far more hallowed scripture than any ever written by the hand of humans.

Joshua trees and extinction

Yesterday’s mail included Keys Views, the membership newsletter of the Joshua Tree National Park Association. (The name is a play on Keys View, a popular viewpoint in the park.) The lead story, entitled “Oh Say Can You See… a Land Without the Joshua Tree?”, describes a study of the potential effects of climate change on the park’s namesake tree species.

From the article:

Predictions of the Joshua tree’s retreat from the Mojave were contained in a 2005 report whose lead author, Dr. Kenneth Cole, is a climate scientist for the federal government’s Colorado Plateau Research Station in Flagstaff, Arizona. Dr. Cole and his colleagues examined climatic conditions within the present range of the Joshua tree; they studied the Joshua tree’s climate tolerances and its potential to shift its range; and then they applied predictionsof future climate change to determine the likely effects of global warming on our beloved yucca grande. To quote from the report:

“The future potential range of [the] Joshua tree (Yucca brevifolia) is not only reduced and shifted northward by climate change, but the plant’s lack of dispersal mechanisms should reduce its actual extent by at least 90%”

Cole et al released some of their data last year in poster form at a meeting of the U.S. Climate Change Science Program in Arlington, Virginia. The maps below are from that poster. First, Cole and colleagues took what we know about current Joshua tree distribution:

20th Century Joshua tree distribution

…which is fairly accurate at this point: scientists have covered nearly every square mile of the plant’s habitat on foot, which wasn’t always the case. Then they took projections of future Mojave desert climate in a world with twice the atmospheric carbon dioxide we had in the 20th century, calculated the likelihood of Joshua tree survival due strictly to climatic factors, calculated the rate at which the trees disperse new seedlings to potentially more welcoming habitat, and mapped the species’ projected range in the mid-late 21st century.

Or they tried to. But the projections didn’t include any Joshua tree stands large enough to show up on the map. So they assumed that the trees would somehow disperse their seeds ten times more efficiently than they have been found to, and they got this map:

projected 21st Century Joshua tree distribution

Even in this extremely optimistic scenario, the Joshua tree will become extinct in Arizona and Utah. No Joshua trees will survive in Joshua Tree National Park, nor will these at my usual campsite on Cima Dome:

cimasunset

The problem is seed dispersal. Joshua trees don’t do it well. Oh, ladder-backed woodpeckers will hammer at fallen fruit to get the worms that live inside, thereby spilling seeds all over, and packrats will pick up seeds and fruit and carry them fifty feet from the tree or so, and there are a few other birds and rodents that play a role in moving Joshua tree seeds around. Every once in a while, a coyote might eat a fruit and shit it out ten miles away. But unless the tree is on a long, steep hill, its golf-ball-sized fruit tend to stay within a few meters of the parent tree. The seeds are large, and seem to have no adaptations allowing birds to carry them long distances by accident: no sticky burrs, no sweet pulp surrounding a gut-proof seed coat, nothing but a delicate little black flake. Most of the time when something eats a Joshua tree seed, it kills the seed.

I started wondering a few years back, as I learned more and more about Joshua trees, whether there might not be some missing puzzle piece. Joshua trees are tall, heavily defended plants with fleshy fruit growing at the top, sometimes thirty feet off the ground. There are quite a few plants in the Americas that, like the Joshua tree, seem ill-adapted to seed dispersal because their fruit isn’t designed for any living animal to disperse efficiently: the Osage orange, the pawpaw, the avocado. Many of these plants have been linked to the giant extinct animals of the Pleistocene, big critters who could denude a pawpaw or avocado tree of all its fruit, walk a ways and excrete the tree seeds, seasoned only slightly by digestive juices. Could Joshua trees be another such plant, dependent for seed dispersal on an animal species that will never come back?

Turns out at least some scientists share my suspicion.

Nothro y nosotros

Nothrotheriops shastense, the Shasta giant ground sloth — pictured here with a couple no-good desert layabouts in a painting by Carl Buell, who by the way started blogging again while CRN was temporarily out of service — lived throughout the range of the Joshua tree in the Pleistocene, up until about 12,000 years ago. That’s recent enough that you can still find its mummified dung in caves in the southwest. Said dung has often been found to contain the remains of Joshua tree fruit, with seeds that likely would have been viable when excreted.

The Joshua tree’s historic range, in other words, may already be a fossil of sorts, an artifact of a relationship with a species that no longer exists. The big problem with extinction is not so much that those species go extinct — though each is a huge loss — but in the extinction of the relationships that species had with every other species it encountered. No species exists in an ecological void, and each provides either sustenance for or competition with many other species. Each species lost is a node untied in that mesh of relationships.

There is nothing to keep Joshua trees from growing well outside their current range. A grove of them has been growing at the Tonopah Airport, one valley north of their present limit, since World War Two. There are mature Joshua trees growing in Ione and Fallon, Nevada, more than a hundred miles north of their current range. The trees would likely find the climate of the hills around the San Joaquin Valley salubrious, and if they dispersed as fast as oaks do they’d be there in fifty years — there are several distinct populations within an hour’s blue jay flight. But unless the scientists’ deliberate optimism pans out, an unlikely prospect, global warming may very well kill off the last of the wild Joshua trees. And that’s not even accounting for increased fire danger, and then there’s the fact that small mammals eat Joshua tree “bark” in dry years, a measure of desperation that may have killed thousands of trees in Joshua Tree National Park alone

I need to get that book written. Major life decisions that would free up writing time have been put off. They can’t wait much longer.