Another upcoming event that may be of interest to DC-area readers of this blog:

Labels: astronomy, evolution, teaching, virginia

From the satiric weekly The Onion: Evolutionists Flock To Darwin-Shaped Wall Stain.

Labels: evolution, humor

I saw Stephen Jay Gould speak once, in 1995 or 1996, at William and Mary. He showed us a series of 'evolution' cartoons, all bearing some humorous variation on the the linear progression of ape-to-australopithecine-to-caveman-to-modern-man theme. Gould used these cartoons an an example of the traditional human way of thinking about evolution: as a linear process leading to us as its final culmination. (Gould argued against this "line" of thought -- suggesting instead that evolution is best thought of as dendritic and arborescent.)

Anyhow: since I saw that talk, I've been very aware of the variety of cartoons on this cliche of a theme. There are a lot of them. I saw another one (by Ward Sutton) this evening while reading this week's New Yorker magazine:

Labels: art, evolution, humor

Browsing around the web this afternoon, killing time when I should be working on my Geotimes cartoon, I came across this essay on the New York Times website: "Musings inspired by a quagga"*, by Olivia Judson. Good stuff, although I do get tired of hearing that old "but the extinction that caused the death of the dinosaurs wasn't even the biggest" cliche. Inspired by a visit to the Museum National d'Histoire Naturelle in Paris, Judson explores the role of extinction in evolutionary processes. Worth a read.

*By the way, mark your calendars: August 12 is Quagga Day, so proclaimed by Ed Abbey. The one this year is the 125th anniversary of the death of the last quagga.

Labels: evolution, museums

Sorry for the lack of posting lately -- end of the semester crunch.

Just thought I'd post a link today, to an article in today's Times looking at some of Charles Darwin's botantical experiments.

Also, if anyone's in the neighborhood, I'll be giving a talk at the National Science Foundation in a couple of hours: "Geology Along the C&O Canal," starting at 12noon at NSF headquarters in Arlington, VA. Free & open to the public. Come one, come all... Sorry for the late notice.

Labels: evolution, plants

You no longer have to trek over to Cambridge University in order to sift through Charles Darwin's notes and papers. Now, it's all online, for anyone to access. The papers are all scanned in, so you can see his actual handwriting, sketches, etc. The image above, for instance, is the first written instance of Darwin's questioning the orthodoxy that species are stable (unchanging) entities over time. If species aren't stable over time, that means they can change over time, and those three words can be condensed into one word: evolution.

Also, NPR did a piece on the material being made web-accessible.

Labels: evolution, websites

It's rare for a terrestrial vertebrate to give up its lungs. But this fellow appears to have done just that. It's a newly-described species of frog from Indonesia. They get all their oxygen through diffusion over their skin surface, including skin flaps coming off the arms and legs. There are a few lungless species of salamanders and as well as caecilians, but this is the first frog: in dissections of eight specimens, nary a lung was found. CNN has more.

Labels: amphibians, evolution

Yesterday, Florida's state board of education felt obliged to stick the word "theory" into their description of the teaching of evolution. See this Reuters article for all the moronic details. Of course, evolution is a theory (i.e. well corroborated by many years of scientific testing & explanatory of a wealth of biological phenomena), so I don't have a problem with this definition per se, beyond exasperation with the motivations for its inclusion. I expect we'll see another lawsuit (a la Dover, PA) regarding this move, but in the meantime, it's an opportunity for science teachers to elucidate the difference between "theory" as it's used in science versus "theory" as it's used in casual conversation. So, the battlefield for teaching proper science shifts from Kansas to Pennsylvania to Florida. What would the Flying Spaghetti Monster say?

Labels: evolution, news, politics

This is an amphibian that you wouldn't want to meet in a dark alley: Beelzebufo, a monster fossil frog from Cretaceous sediments in Madagascar. It resembles the ceratophryine family of horned toads (sometimes dubbed "pac man frogs") that are now unique to South America, which the authors of a new study published in the Proceedings of the National Academy of Sciences.

Here, artist Luci Betti-Nash's whimiscal painting of Beelzebufo has it facing extant species Mantidactylus guttulatus, the largest frog in modern-day Madagascar.

The discovery of the big croaker suggests that South America and Madagascar were linked landmasses for much later than previously deduced from other lines of evidence. However, the newly-implied gap in time is substantial. Previously, it was inferred that the two landmasses separated 120 million years ago (Aptian), but the interpretation of this new fossil is that it must have been after 80 million years ago (Campanian). I'm not sure I buy that huge jump in separation dates based on a single genus of fossil frog: 40 million years is a substantial amount of time. On the other hand, sometimes "small" pieces of evidence like this lead to the development of new paradigms in scientific thinking. It has the potential to be the proverbial thread which unravels the sweater.

My caution: It's important to remember that fossils which resemble one another don't necessarily imply a continuous population: there's convergent evolution to consider, as well as the possibility of a highly conserved morphology over time. Both of these phenomena could maintain similar looking populations of "pac-man-esque" frogs on unconnected landmasses. And, I suppose, there's even the less-likely possibility of a "rafting" incident, where a few individuals ride a mass of vegetation across the ocean(s) from South America to Madagascar well after the two have separated. It happened to iguanas, after all: getting from South America to the Galapagos. Actually, with amphibians, their eggs can sometimes hitch a ride on bird feet too, colonizing distant new areas with ease. I'd like to know more about the presence or absence of relevant fossil frogs in Africa during the Cretaceous in order to better evaluate this new interpretation.

Read more about it in this New Scientist article. (I couldn't find the "cited" original article in PNAS, for some reason.)

Labels: amphibians, evolution, fossils, plate tectonics

I have a confession to make. Geology was not my first love: birds were. I spent one summer in college watching cattle egrets. That research project helped me get into ornithology, & I've kept "birding" as a hobby ever since. Even these days, I don't usually manage to get through a geology field trip without pointing and shouting "Look! There goes a pileated woodpecker!" (or a Cooper's hawk, etc.) Birds are everywhere, and they're great.
Accordingly, I was pleased to get these photos Friday from my colleague, NOVA biologist Bill Gorham.

This is a female cardinal (Richmondenis cardinalis). She has a unique look: her head is white! Bill calls her Ms. Whitey.

He tells me that the bird "has been a visitor in my yard for over a year. Last winter she just had a white 'collar' around her neck, then during the summer her whole head gradually whitened."
Bill continues: "I understand the term 'leucistic' applies because it is certainly not albinism but a loss of all pigments in certain areas... I would have to guess that the progressiveness has something to do with maturity. She mated and had chicks this past summer but I think she was a youngster last winter. She is also a member of a local tribe of cardinals that get bald every summer in July and August. First it was just one male (who we called 'Baldy') but now there are several males and several females. I don't think it is mites; I think it is some kind of heat response. When they molt in the fall they get a full head of feathers again."

A few points to be made here: (1) I like sharing images of natural oddities, which is why I'm posting these images [with Bill's permission] here; (2) I like having colleagues who share images of natural oddities [I like the fact I'm part of a community of people at NOVA who are curious about the natural world] and (3) I want to know what the heck is going on with this bird: I think it's weird that it's progressive whitening like Bill describes. I mean, I can see a certain region of the cardinal embryo mutating a gene (which subsequently gets copied & copied) leading to albinism in certain portions of the body (which then remain constant over the bird's life), but I find it truly odd that the area lacking pigment has increased over time. That's remarkable! If anyone has any insights into this "rare bird," let's hear it...

Labels: birdies, evolution, nova

In the spirit of the day, check out this article about mating at the National Zoo, here in DC (and a literal stone's throw from my apartment window).

Among the information featured:
when two females cheetahs are housed together, one or both females will shut down their ovulation, which makes it impossible to breed them until they are again separated.

Shanthi, the baby Asian elephant (who's now almost as big as her mom), was the result of artificial insemination. I remember visiting the Zoo shortly after Shanthi was born, and seeing video footage of her birth. Wow! Kablooey! That's a big package to drop!

The male Panamanian golden frog (pictured), which is extinct in the wild, will attach itself to the female for up to 120 days to make sure he's the one to fertilize her. Talk about clingy!

Also, you may be interested to know that some lowland gorillas will mate face-to-face, as the Wildlife Conservation Society reported this week, and was subsequently promoted by National Geographic.

Labels: dc, evolution

For Christmas a couple of years ago, I gave my family the black death, ebola, flesh-eating Strep, and stomach ache. Lest you think me some horrible person, I should point out that all of these nasty afflictions were represented by cute plush toys, courtesy of Giant Microbes. A picture of their version of E. coli (a.k.a. "food poisoning") is shown at left. They even have a toy version of the "bacterium" found in Mars meteorite ALH 84001!

I recently got an e-mail from the Giants Microbes people, and it reminded me of their unique products. I think they're great, and I just thought I'd pass that on. Several years ago, when I took a cross country road-trip, a Shigella bacterium from Giant Microbes was the Westy's trip mascot. Choose your microbe, folks. Make sure you wash your hands after playing with them.

Labels: evolution, products

First things first: colugos (pronounced cho-LOO-gos) are not "flying lemurs." Though they've been dubbed that, they are not lemurs, and they don't fly. They do glide, however, and that's what we're going to focus on today.

A few years ago, I visited the Malaysian state of Sarawak, on the island of Borneo. While there, I spent a couple of days in Bako National Park, a coastal forest park. Bako was great: bearded pigs, proboscis monkeys, pitcher plants: there was a bunch of cool, weird biodiversity there. One evening, while wandering back to my cabin, I saw some guys with spotlights roaming around in the forest. They were filming something up in the trees. These spotlights they were using were bright: it was professional gear. I asked who they were, and what they were looking at. Turns out they were from the BBC, filming an arboreal animal for footage to be included in a new program. This program was later watched by millions of people around the world: it was the groundbreaking series Planet Earth. The animal the Planet Earth team was pursuing in the forest was the Malayan colugo (Galeopterus variegatus).

Late last year, in Science, a study of a genetic marker shared by colugos and all primates established that the colugos were our order's closest living relatives, from which we diverged about 90 million years ago. They are fascinating creatures, even aside from this sense of kinship. I've seen colugos in two other places besides Borneo: Palau Tioman (off Peninsular Malaysia's east coast), and in Singapore (at the Zoo, but the colugos there are wild and uncaged). Each time, I've been astonished at how odd they look: clutching a tree they look like Gollum from The Hobbit: a srawny furry thing with improbably wide eyes. But then they launch themselves into the air, and they are transformed into a sleek gliding thing, like a swift kite, or an aerodynamic doormat. They slice through the air surprisingly quickly, and then flare up (stalling) just before their chosen tree, which they then land on. They crawl up the tree to a higher level on the trunk, and then repeat the gliding act.

A new study in the current issue of Proceedings of the Royal Society addresses the kinetics of colugo flight. Researchers captured a few colugos, shaved their backs (hah!) and then glued a little accelerometer there. This accelerometer works in the same way as the new generation of video game controllers: basically it can sense in what direction the colugo is moving, and how fast it's moving in that direction. The device looks like a little jetpack on the back of the colugos (as in the photo above), and it makes them look like some race of alien: a combination of the weird almost-a-primate morphology coupled with the shiny technological gadget latched to their backside. I'm not sure that I find the insights of the study all that fascinating (they basically confirm my common-sense read of colugo flight dynamics), but I think it's cool that people are out there quantifying such things using technology like this.

Accelerometer article in Proceedings of the Royal Society B.

Genetic relatedness of colugos to primates article in Science.


Eurekalert press release on the accelerometer study.

Labels: evolution, primates, tv

A paper in the new issue of Proceedings of the Royal Society announces the discovery of fossil evidence of the largest rodent yet recorded by science. The fossil reported is a skull, found in Uruguay. Of course, South America is home to the largest living rodent (the capybara, Hydrochoerus hydrochaeris), and it's no surprise that the continent should also have been home to the largest fossil rodent. The reason is that South America was a hotbed of mammalian evolution from about 65 million years ago (Ma), when it separated from North America, until about 3 Ma, when it reconnected with North America via the narrow Isthmus of Panama.

The new species, dubbed Josephoartigasia monesi, is closely related to another large extinct rodent called Phoberomys pattersoni as well as an extant (still living) species known as a pacarana (Dinomys branickii). The image at right, from the paper, shows a reconstruction of the head of J. monesi and a comparison with a pacarana.

P. pattersoni (from Venezuela) is estimated to have weighed about 700 kg, while J. monesi's bulk (extrapolated from the relative size of the skull) must have been about 1000 kg, a full metric ton.

As a continent hosting an independent trajectory of mammalian evolution, South America offers a beautiful contrast to Australia. Both continents were isolated from other continents for tens of millions of years, and their particular blend of mammals (& other species) evolved into unique & interesting forms. The South American experiment ended when it reconnected to North America at 3 Ma. At that time, mammals from North America trooped southward through Panama, and mammals from South America trooped northward. This flux of biodiversity is referred to as the Great American Faunal Interchange, and it dramatically reshaped South America's mammal assemblage. Saber-toothed cats (Smilodon sp.) was one of the turistas from the north, and it likely fed on big fat critters like J. monesi.

Other southward-bound groups included deer, bears, squirrels, rabbits, raccoons, and camelids (which went on to diversify into llamas & their kin). Northward-bound groups colonizing North America were fewer in number: the armadillos, the opossum, ground sloths (now extinct), and porcupines. Today, about 50% of South American mammal species have a North American origin, while only 20% of North American mammals have a South American origin. One of the reasons suggested for this lopsided distribution was that North America had been periodically connected to Eurasia (both east and west) via landbridges during the Cenozoic, and therefore North American mammals had been continually tested against the biggest continent's most competitive species. The North American mammals had already been forced to prove their mettle. South American mammals were living a life of blissful ignorance & luxury, and they experienced a rude awakening when their neighbors from the North came stampeding in. The competition between the two groups resulted in a lot of extinctions, and one of those appears to have been J. monesi. The fossils were found in a sedimentary unit usually interpreted to be about 2 Ma.

The image below shows the sheer size of the J. monesi skull by comparing it to a handheld rat. (Maybe a Norway rat? I can't tell, and the image from New Scientist doesn't specify the species.) It's a pretty extreme difference, of the same order of magnitude as the difference between an elephant and a hyrax.


Evolution can be really fruitful given a sufficient easing of competitive pressure. Island biogeography gives us some weird creatures (Komodo dragons, dwarf elephants, and Homo florensis come to mind as three Indonesian examples) if isolation is maintained over time. This new discovery from South America confirms the larger pattern by showing us that gigantism has happened in the rodent family, too. Discoveries like this (and the recent giant ape reported from China) prompt me to imagine other possible evolutionary trajectories: what about giant bats, or mouse-sized whales? Could evolution produce arboreal deer, or bears the size of Chihuahuas? I welcome your thoughts & creative speculations on potential record-breaking mammals.

Reference: Rinderknecht, Andres, and Blanco, R. Ernesto. The largest fossil rodent. Proceedings of the Royal Society, B. doi:10.1098/rspb.2007.1645 Published online.

For those without a subscription to the Proceedings, you can check out New Scientist's write-up of the research here.

Labels: evolution, fossils

In last week's issue of Science, Paul Silver (of DC's own Department of Terrestrial Magnetism at the Carnegie Institution) and Mark Behn (formerly a post-doc at Carnegie, and now at Woods Hole in Massachusetts) published a paper putting forward an intriguing idea: maybe plate tectonics proceeds in fits and spurts.

Silver and Behn note that most of the world's subduction zones are located in the circum-Pacific belt, and that the Pacific is getting smaller over time. (Subduction destroys oceanic crust, and since the Earth presumably isn't increasing or decreasing in volume, subduction in the Pacific is balanced by seafloor spreading elsewhere, like the Atlantic.)

The Pacific is "predicted" to close in about 350 million years, assuming that the tectonic plates continue to move at about the same rate they're moving now. The death of the Pacific would come as the Americas smash into eastern Asia and Australia, raising up a Himalayan/Appalachian style mountain belt. Silver and Behn posit that this would basically end subduction on planet Earth for a time. This was a startling idea to me at first, but then I thought, "Why not?" Then I thought, "I wish I'd thought of that."

My understanding of mountain belts comes from the Appalachians, which built up in three successive episodes called orogenies. Check out the diagram below (from the excellent textbook Essentials of Geology by Steve Marshak, that I use in my Physical Geology course at NOVA) and follow along so you can see why this new concept startles me a bit (but in a good way):

There used to be a big ocean basin off the "east" coast of North America that closed via subduction over the course of the Paleozoic Era. This extinct ocean goes by the name of Iapetus. This was not a simple event: it was more like a pile-up on the highway than a simple head-on collision. This ancient ocean basin was not just empty ocean. It also included islands and small chunks of continental crust ("microcontinents" like modern-day Madagascar). First a subduction zone developed out there in the ocean, closing a portion of it. This brought a chain of volcanic islands closer & closer to North America. The islands hit North America (around 460 million years ago), in a mountain-building event called the Taconian ("Taconic") Orogeny. Once that had happened, a new subduction zone developed on the ocean side ("outboard") of the islands/accreted terranes. That began to close another part of the Iapetus Ocean. Around 360 million years ago, that episode of subduction ended when a microcontinent (dubbed Avalonia) smacked into North America. This collision caused more mountains to rise: the Acadian Orogeny. Then yet another subduction zone, outboard of the newly accreted Acadian terrane, kept the closure of the Iapetus Ocean going, until finally the continent on the other side of the ocean (Africa) smashed into North America, raising more mountains. This is the Alleghenian Orogeny (sometimes spelled "Alleghany"), which really crumpled up the landscape, starting around 300 million years ago. The moment the Iapetus died was the moment Pangea was born.

I go into all this because the model of plate tectonic convergence the Appalachians display is one that says collisions between plates don't stop the overall convergent forces. As soon as one subduction zone is snuffed out, a new one develops outboard of the continent, where the weaker, denser oceanic crust gets shoved downward.

But does it actually work that way all of the time? Silver and Behn suggest maybe not. Maybe it's an "on-again, off-again" affair. They cite among their evidence an earlier orogeny, the Grenville Orogeny, which sutured together many continents at a much earlier time (about a billion years ago). When that collision had ended, the supercontinent Rodinia was born. Silver and Behn note a lack of volcanic activity around the world for hundreds of millions of years after the Grenville Orogeny (most volcanoes are caused by subduction). Rodinia did eventually break up amid much volcanic activity (including the eruption of the mid-Atlantic's infamous Catoctin Formation), and giving birth to the Iapetus Ocean basin in the process -- but that didn't happen for a long time after Rodinia got assembled. What gives? Does that mean subduction was inactive during that period?

They also offer a modern example: India and the Himalayas. 20 million years ago, India was a microcontinent out in the Indian Ocean, with a pavement of oceanic crust separating it from Eurasia. India moved north, the oceanic crust got subducted, and eventually India plowed into Eurasia, raising the Himalayas. But why hasn't a new subduction zone developed south of India? That would be what would happen if India's orogeny were following the Appalachian example.

Maybe plate tectonics has periods of intense activity (lots of subduction), but then has periods where it's "clogged up," and the movement of the plates slows. Eventually heat builds up in the underlying mantle (the source of plate movement) to the point where the mantle begins to convect more vigorously, and the plates start getting dragged around again. It's kind of a cool notion. I'd be interested to hear what you think about it. Please post any thoughts you have in the comments section below.

The whole idea reminds me of the concept of punctuated equilibrium, a model of biological evolution which bucked the long-standing notion (originated by Darwin himself) that evolution proceeded slowly and methodically over time. Thanks in part to an eye-opening appreciation of the Earth's immense age, the prevailing wisdom was that evolution was gradual, smooth.

Then (in 1972) Niles Eldridge and Steve Gould published a landmark paper that suggested otherwise. Instead of "gradualism," they argued, changes in populations of living organisms may have happened suddenly, experiencing a lot of change in a short period of time. Once equilibrium was achieved, the new status quo was preserved as a non-dynamic scene for a long time. (See image at left, which came from Wikipedia).

They cited the fossil record as their primary evidence: most of the change seen in fossils is a sudden switch of biological "regimes," with new fossils showing up, lasting a while, and then abruptly vanishing. I'm oversimplifying here, but I hope the analogy is clear: if evolution can do it, why not plate tectonics? Is there any reason to think plate tectonic motion couldn't happen in spurts of more activity followed by periods of quiescence? Ponder it...

Reference: Silver, Paul G., and Behn, Mark D., 2008, Intermittent plate tectonics?: Science, v. 319, p. 85-88, doi: 10.1126/science.1148397.

For those without a subscription to Science, you can read the press release about Silver and Behn's work that Carnegie put out by visiting their website.

Labels: appalachians, evolution, iapetus, plate tectonics

An article in the current issue of Current Biology describes a fascinating experiment with profound results. Like the best science, the experiment is simple and elegant. Researchers took blind cave fish from two different cave systems and mated them. The offspring had fully functional eyes. It turns out that different parts of the developmental system had broken down in the eye-producing mechanisms of these two different fish populations. In essence, they represented two different evolutionary trajectories. Technically, a certain spot in the genes for making one part of the eye mutated in one population of cave fish, and another spot (or "locus") mutated in a second population. The fish were both blind, but they were blind for different reasons. What was wrong with one was right with the other, and by breeding them good genes cancelled out bad, at least in some of the offspring. The remarkable implication is that researchers produced sighted fish from two populations that hadn't seen in over a million years! It's a powerful confirmation of their independent origins in different cave systems -- basically a subterranean example of how evolution takes populations of organisms in different directions based on their own individual circumstances and histories.

A summary of the work is found at National Geographic's website, for those of you who don't subscribe to Current Biology.

Labels: caves, evolution

The National Academies of Science released a new book yesterday about evolution. Aimed at the layperson, it explores the molecular, organismal, and fossil evidence in favor of evolution. The book suggests that accepting this evidence does not require losing one's religious faith, but instead that the two are compatible ways of viewing the world. The book is entitled "Science, Evolution, and Creationism." A PDF brochure offering an overview of the book is here, and the book can be ordered online here. Perhaps as a sign of things to come, the entire book is also available online, and you can access it here.

Labels: books, evolution