Blue Collar Scientist

NewsDaily, Shortnews, and a bunch of other outlets are reporting that Rhys Nichols has discovered dinosaur tracks while walking on the beach near Scarborough, North Yorkshire, with his father. Rhys is eight years old, proving the oft-repeated adage that paleontology and astronomy are the two disciplines to which amateurs commonly make scientific contributions.

It is reported they are probably Iguanodon tracks from the Jurassic.

“This is a great find as dinosaur prints are not normally that clear,” archaeologist Will Watts said, “Looking at the size of the prints, the dinosaur was probably the same size as Rhys.”

Umm - archaeologist?

Microraptor fossil. The image is from Wikimedia Commons, where it is licensed under the Creative Commons Attribution ShareAlike 2.5 license. Unfortunately, no author name is provided.

I’ve just finished watching the latest Nova, which aired last night (all praise be to TIVO). The episode was about Microraptor.

The early part of the documentary set up some controversy by contrasting the ideas of Larry Martin with those of various AMNH paleontologists and staff, and their collaborators at other institutions. Martin proposes that the development of flight from ground-dwelling dinosaurs¹ doesn’t make much sense, without really giving any compelling reasons. He also says that this model is necessary for the evolution of birds from dinosaurs, and again, I don’t fully understand why he thinks that. As I’m fond of saying here, just because you say something doesn’t make it true. I’m unable to think of a reason that arboreal dinosaurs developing flight means that birds can’t have evolved from dinosaurs.

He did make a reproduction of Microraptor which featured splayed femurs. The documentary covered pretty convincingly why the reproduction was not plausible - even I could see that Martin’s pelvis was flatter than a pancake. The documentary covered the similarity of the splayed rear-limb model to lizard anatomy, but I don’t think I really understood why Martin believed - even if everything else he said was true, which I wasn’t convinced of - that Microraptor could not have secondarily splayed rear limbs.

Anyone?

The AMNH team certainly seemed to be doing the better science from what Nova presented. Not only was their model constructed with some pretty rigorous methods, they recruited a multidisciplinary team of experts in various fields and hiked out to a wind tunnel to test it. It made Martin’s approach look a bit parochial. The latter half of the documentary seemed to abandon any further coverage of Martin’s work.

The wind tunnel scene was pretty interesting. I’ve been part of similar groups of scientists trying out and testing new ideas, and what Nova showed is pretty much how scientists act - on the whole very competitive, but very collegial and with few exceptions willing to admit it when the data proves them wrong. As usual, Nova was well worth watching.

1. the “ground-up” model, as he puts it, which for some reason has me picturing dinosaurs flying into airplane propellers end ending up as ingredients in my hamburger [↩]

The latest Four Stone Hearth carnival is up at Archaeoporn - have a look!

Researchers at the University of Oslo Natural History Museum have announced the discovery of an enormous marine reptile - a 50-foot (15 meter) pliosaur.

The pliosaur was found in the arctic island chain of Svalbard (the BBC reports it was found on Spitzbergen) by a “team of Norwegian paleontologists and volunteers from the University of Oslo Natural History Museum” and their principal investigator, Jørn Hurum. But at least one Alaskan, Patrick Druckenmiller, was involved with the find. A plesiosaur specialist at the University of Alaska Museum, he’s quoted in the press release as saying:

“Although we didn’t get the entire skeleton, we found many of the most important parts, including portions of the skull, teeth, much of the neck and back, the shoulder girdle, and a nearly complete forelimb (paddle)” said Druckenmiller, “Amazingly, the paddle alone is nearly 10 feet long.”

In a bit of a departure from established taxonomy practices and the usual reticince to announce such things before a paper has passed peer review, the PI says:

“From the bones we have finished stabilizing so far this absolutely looks like a new species” Jørn Hurum tells enthusiastically.

The fossil is 150 million years old, putting it in the late Jurassic.

One of the things interesting to me about this find is how many significant fossils are coming out of the arctic or nearctic in the last decade or so. Finds like Tiktaalik roseae, the Axel Heiberg champsosaurs, the Victoria Island acritarchs, the Colville River finds, the Bathurst Island vascular plants, Greenland’s Ichthyostega, and so on. This could be for any or all of a number of reasons:

• The arctic is well-mapped geologically, mainly by the oil companies, allowing paleontologists to conduct well-planned digs at carefully selected locations.
• More easily accessible areas are already pretty well prospected.
• Arctic areas don’t have a lot of trees on the ground to interfere with access to fossils.
• Until relatively recently, access was prohibitively expensive, especially if you wanted to transport fossils out.
• In this case, the Svalbard Tourism Board made the prospect of a working vacation irresistable.

Anyway, now we can chalk up another interesting arctic find. According to the BBC, they’ve done a literature search, and this is apparently the biggest pliosaur ever.

Boneyard XIV is up at Self-Designed Student - go check it out! There’s some great paleontological posts there, well worth the reading. Past and future carnivals are available at the Boneyard.

I recently did a little public outreach about astronomy, and because there were no clear skies to be had, we did a little lecture and question-answer session instead. In the last year or so, I’ve been making it a habit to start off the talk with a brief presentation on an unrelated science subject that is in the news. This time, I talked about Mesozoic crayfish and trace fossils from Australia. I hope to have the presentation file downloadable from here shortly; stay tuned.

Regular readers might remember that I covered this subject before - and now I have more of the story.

Dr. Anthony Martin, paleontologist at Emory University, is an acknowledged expert on trace fossils - that is, fossils that don’t preserve the body of an organism, but do preserve some indication of its anatomy and its behavior, such as footprints, burrows, and droppings. He’s also an expert about dinosaurs. He’s written important books about both subjects, as well as being heavily published in journals, mostly as the principal investigator.

He visited the Dinosaur Dreaming fossil site in Australia back in February, 2006. As he was walking around looking at the site on his first day, he discovered two large theropod dinosaur tracks. On the second day, he found a complex of crayfish burrows.

Crayfish burrows, 116 million years old, from Dinosaur Dreaming, Victoria, Australia. The scale card in this image is 10 centimeters long, or about four inches. Photo courtesy of Anthony Martin. Click to enlarge.

Paleontologists had been walking past the burrows for fourteen years, but either nobody noticed them, or nobody appreciated what they were. Martin saw them mainly because he was experienced and educated about what to look for - as they say, luck favors the prepared. At about 116 million years old, the burrows were an important find. Crayfish currently live on every continent except Antarctica and Africa. But many of the continents that crayfish are found on today are separated by large expanses of salt water, where crayfish can’t survive. Therefore, scientists thought that crayfish evolved and dispersed at a time when the continents they are found on were crammed together.

At the end of the Jurassic and beginning of the Cretaceous, Australia, Madagascar, South America, and India were all connected, but they had begun to move apart. If southern hemisphere crayfish had originated in Australia in the early Cretaceous, they would have had only a short time to expand to other continents. If this hypothesis were true, it suggests some specific predictions that could be made: Africa was already separated, so they wouldn’t be found there - and they aren’t. They might not have had enough time to make it to India, so they may not be found there either. It turns out that crayfish aren’t found in India, and neither are their fossils. So far, so good. And crayfish are found on Madagascar, South America, New Zealand, and Australia - all of which were connected, so this is consistent with the continental features of the time.

Another prediction can be made from this scenario: If southern hemisphere crayfish originated in Australia and expanded out from there, it would make sense if Australia to had more crayfish species today than its southern hemisphere neighbors. If it didn’t, that wouldn’t falsify the hypothesis, but if it did, it would lend it some support. And it turns out Australia does have more crayfish species - about 85% of all southern hemisphere crayfish species are found there.

There was a problem, though: although some crayfish fossils from around 150 million years ago are known from the northern hemisphere, none older than about 40 million years had been known from any of the southern continents. If southern hemisphere crayfish originated in Australia, the prediction of evolutionary theory and the theory of plate tectonics would be that crayfish body and trace fossils should be found from the early Cretaceous in Australia - fossils from sometime before 90 million years ago.

So with this discovery of 116 million year old crayfish burrows, these predictions are fulfilled. The burrows are of the right size and configuration for crayfish, and no other organism is known to produce just this morphology in their traces. In addition, the geology of the area supports a freshwater habitat favorable for crayfish. Everything was pointing to a significant find.

Having recognized the crayfish burrows, Martin asked the site director, Lesley Kool, the obvious question: “Do you have any crayfish body fossils from here?” It turns out they did not, but a crayfish body fossil had been dug up in Dinosaur Cove, another fossil site in Victoria, almost twenty years before. It had been sitting in the Museum of Victoria unstudied all that time.

Crayfish fossil, 106 million years old, from Dinosaur Cove, Victoria, Australia. Photo courtesy of Erich Fitzgerald.

One of the remarkable things about this fossil is how close it came to being destroyed by a rock saw. You can clearly see the slot sawed into the rock coming up from the bottom of the picture, slicing through the pincer, and heading toward the crayfish abdomen. There’s another saw cut that took out a chunk of rock that made up this crayfish’s upper back. It just goes to show that not all fossils - and not all important fossils, at that - are as clean and polished as the dinosaurs we see in museums. In addition to this fossil, fossilized claws from two other crayfish were found in the museum’s collections.

So, as a result of happening across the burrows, which led to asking about body fossils, Dr. Martin was able to describe the only crayfish fossils from the age of the dinosaurs in the southern hemisphere. Having written the paper, he saw it rejected twice, but got it published on the proverbially charmed third try.

In such haphazard ways is human knowledge advanced. In a lot of cases, paleontologists have already found interesting and important fossils - they just haven’t had an expert on that field around to recognize them or appreciate their significance. Gaps in our knowledge are caused not only by not having discovered important fossils (yet!), but also by not having studied the ones that have been discovered. This is how science works - it isn’t always in clean labs with white coats and microscopes, and it isn’t usually with perfect specimens. Sometimes it is considerably harder - and luckier - than that.

Andrew Kitchen, Michael M. Miyamoto, and Connie J. Mulligan report in PLoS-ONE on their development of a three-stage model for the colonization of the Americas by Homo sapiens. This issue is of deep interest to anthropology outreach in Alaska, and I’m accordingly very interested in the paper. The attention that these ideas will likely receive in Alaska suggests several major avenues for effective public outreach:

• It provides an opportunity for “what is the nature of science and knowledge” education. The concepts of falsifiability and refinement of knowledge over time are particularly rich opportunities with these new results.
• It provides an opportunity to provide some “cutting edge” science to students. As noted below, many of the interpretive materials in greater Anchorage on these subjects reflect what was “cutting edge” twenty years ago, but which is now largely rejected in paleoanthropology.
• This paper is largely about analysis of genetic populations, and statistics. Therefore, it is an open door to talk about mutation rates and evolution, and some simple statistical exercises could easily be devised to give students an idea of what the authors are doing in their analysis.
• It provides an example of multidisciplinary work in science. The authors present a genetics analysis but subject it to controls imposed from other fields.
• Because some broadly similar studies of the past have not been subject to those controls, it provides an example of why there might be apparent disagreement about knowledge amongst scientists. For example, I’ve heard about genetic data that supports migration into the Americas both much earlier, and significantly later, than well-dated archaeological sites. By not imposing constraints from other fields of study, such findings result in apparent disagreement, without necessarily being valid disagreement. The distinction is worth teaching since organized antiscience uses such cases as a wedge.

The authors propose that the population of Amerind ancestors expanded out of east central Asia between 43,000 and 36,000 years ago, and occupied Beringia, the easternmost portion of Asia and the western part of Alaska, including the sea floor which was exposed at the time. A stable population of 8,000 to 10,000 people remained there from that time until around 16,000 years ago, at which time 1,000 to 5,400 of them rapidly expanded into the Americas. The study conforms to prior hypotheses that this expansion occurred either through an ice-free corridor in eastern Alaska and western Canada, or along the coast.

Consistent with other recent work, this paper proposes a single migration, as opposed to studies of the past that considered Amerinds, Na-Dene, and Eskimo-Aleuts to be the result of different migrations. This hypothesis gained popularity in the mid-1980’s, and is the model adopted by a number of interpretive materials in and around Anchorage. The model has been in disfavor for some time in the professional literature, and it seems likely that this new study would help to change these interpretive aids (assuming that scientific evidence trumps political expediency).

The authors point out that the genetic studies to date have strongly supported a single-migration model, but that they have varied significantly concerning the proposed date of the migration, with dates anywhere from about 13,000 years ago, to 40,000 years ago. As a result, that data has been interpreted by a variety of scenarios involving additional migrations, migrations of various ages, and so on. At least from the layman’s perspective, many of these seemed like clever possibilities that had the unfortunate air of being ad-hoc about them.

The new study accommodates some of the more puzzling aspects of the prior genetic studies, particularly ones that come up with very old dates of 30,000 years or more for the migration. A stable population in Beringia for some thousands of years would explain those results, and also explain why there are no American archaeological sites older than around 15,500 years old, while accommodating nicely the archaeological evidence that Homo sapiens was in northwest Beringia by about 30,000 years ago.

The study incorporates data from both nuclear and mitochondrial DNA of both Native Americans and Asians. Mitochondrial DNA evidence was cited in 2005 (with quite a bit of publicity, at least in Alaska) to support the idea that the population colonizing North America was extremely small, so it appears to me that the re-analysis of the mitochondrial data is of particular interest. Also of interest is that this study, unlike some in the discipline, uses archaeology, geology, and paleoecology as opportunities for imposing controls on the analysis of the genetic data. Some of the genetics studies of the past have given the appearance of being statistical analyses that avoided giving very much consideration to what is known from other disciplines. The study constrains divergence time to 15,000 years ago, and by trying out different migration rates between Asia and Beringia (and back), it is shown that the lower (and “more biologically realistic,” as the authors put it) the migration rate the larger the population of Amerind ancestors:

Our results demonstrate that smaller estimates of Ne depend upon a substantial level of migration from Asia to account for present-day levels of Amerind genetic diversity, e.g. Hey’s estimate of ≈70 founders is associated with a mAsia→NW > 9.0, which is twice the migration rate for contemporary Europe (m = 4.3).

Emphasis mine. I agree with the authors that the high migration rates assumed by other studies are implausible. Intuitively, I have a hard time accepting that the rate of migration on a modern industrial continent serviced by jets and trains is substantially lower than that found in east Asia in the Pleistocene, but I’m not an expert.

The authors also build into the paper a very nice opportunity for those doing outreach to talk about “what is science:”

Our goal is to provide a comprehensive model for the initial settlement of the Americas that generates new testable hypotheses and has high predictive power for the inclusion of new datasets. In light of our results, we propose a three-stage model in which a recent, rapid expansion into the Americas was preceded by a long period of population stability in greater Beringia by the Paleoindian population after divergence and expansion from their ancestral Asian population.

In other words, science produces conclusions that are testable. When you come to a conclusion, you are sticking your neck out a bit - because by definition a scientific finding is subject to being disproved at some point by someone who has better data, or is better at interpreting your data than you are.

One of the most interesting aspects of this paper, from an outreach perspective, is the opportunity to discuss how we know the dates. Here in a single paper are incorporated various methods for dating prehistoric events and materials (carbon dating, stratigraphy, genetic statistics, and surely a few others), and all of the methods agree that this recent event in world geological history still took place thousands of years before some believe the world was even created. The contrivances that are required to refute these vastly different, yet mutually-supporting dating techniques are awesome in their implausibility, and that’s where the teaching opportunity comes from.

–

This blog article is about:

Kitchen, A., Miyamoto, M.M., Mulligan, C.J., Harpending, H. (2008). A Three-Stage Colonization Model for the Peopling of the Americas. PLoS ONE, 3(2), e1596. DOI: 10.1371/journal.pone.0001596

Intelligent Design Creationists have said for some time that bats pose a problem for evolutionary theory.

Things are even tougher for the evolutionist with the knowledge that the ‘oldest known’ complete fossils of bats … show indications of a fully-developed echolocation system.

Evolutionary theory predicts that in such cases, transitional forms did exist, and are possibly waiting to be discovered in the fossil record. And today, Carl Zimmer reports on his blog about a newly discovered bat fossil.

The ear bones in its head don’t have the distinctive shape found in living bats that echolocate, suggesting that it had to rely on sight and sound to catch prey–insects, judging from its teeth. Flight evolved first in bats … and echolocation only came later.

Oh. That must really suck to be an intelligent design creationist who thinks that bats popped out of nowhere with echolocation fully developed, then.

It turns out this bat fossil is the most primitive bat ever found, and it has several other transitional attributes:

1. Evolutionary theory predicts that early bats would have body proportions similar to that of the walking mammals from which bats evolved. This fossil has shorter arms, and longer legs, than modern bats. Prediction fulfilled!
2. Almost all modern bats have only a single claw. Evolutionary theory predicts that early bats should have a full compliment of claws, and that bats who lived in between these times should show a gradual loss of claws. Many bat fossils are single-clawed with vestigial claws on other fingers, thus fulfilling the prediction as far as was able. But this bat completes things - it has claws on all five fingers, just like evolution predicts.
3. Evolutionary theory predicts that as a lineage evolves flight, early fliers will be less strong, less powerful flyers than later ones. Some evolutionary biologists have also hypothesized that powered flight most likely evolved from early gliding. Most modern bats fly with a full-time power stroke, flapping their wings continually during flight. But this fossil’s wings suggest that it alternated between flapping and gliding. Prediction fulfilled!

This is just a summary - go read Carl’s story. It’s outstanding, and it has pictures.

The BBC, LiveScience, and others are reporting on the discovery of a new pterosaur found in north-east China. The find also confirms a prediction of evolution. From the BBC story:

“It is very likely that this pterosaur represents a lineage of arboreal creatures that lived and foraged for insects in the gymnosperm forest canopy of north-east China during the Early Cretaceous,” the researchers write in PNAS.

They conclude this from curved bones in the feet, which are similar to those found in perching birds. This pterosaur is also smaller than most others, of a size that makes sense for perching on branches. Cladistics suggest that this pterosaur was close to the ancestors of the giant pterosaurs, including Quetzalcoatlus, which had a 30-foot wingspan. Thus the new fossil is transitional, being in some ways less derived than later specimens but more derived than the pterosaur’s hypothesized concestor.

“It is interesting to see some clear arboreal adaptations in this species,” said [Smithsonian paleontologist Matthew] Carrano, who was not on the research team.

“It confirms a suspicion we had, that pterosaurs were more diverse in their habitats than we knew from the [fossil] record.”

Let’s be a bit more direct here, in the interests of effective science outreach and clear communication. The notion that pterosaurs were more diverse (in their habitats, or in their phenotype - both apply) than the fossil record previously demonstrated is a prediction of evolutionary theory, not merely a suspicion of paleontologists. There are actually two predictions here, both of which are confirmed by this fossil.

1. Evolution predicts that some species will be absent from the (known) fossil record, and that some of them, if they were known, would illuminate the evolutionary development of their lineage. Here we have an example of a fossil which was unknown until recently, and which does just this. Score one for evolution.
2. Evolution makes the more specific prediction that, when you have lots of fossils of lots of species with specialized adaptations - such as pterosaur fossils - that less derived species will exist earlier in the lineage. Not only that, but it says that most of the characteristics that are common to most or all of the more specialized species will be present in the less derived one. Again, from what’s been published, this fossil confirms this prediction.

Seems I’m on a paleontology kick lately. Undoubtedly this is a result of spending so much time in museums over the last month, looking at fossils. Fair warning - there’s at least one more of these in the pipeline. I’ve had some interesting information and photos from the PI of the crayfish fossils I reported on earlier that I’m working up.