MoO 2013 - pathological rodent teethAnother nice display from the Museum of Osteology in Oklahoma City (previous MoO posts here and here). Check out the really gnarly ones that are indeed growing right through the bones of the face. That must have sucked.

We’ve covered rodent teeth here a few times before (one, two)–more than is probably right, for a blog ostensibly about sauropod vertebrae. Sherlock Holmes said, “Life is a great chain, the nature of which can be determined by the discovery of a single link.” I’d amend that to, “Life is a great tree, the inherent fascination of which flows through every tiny twig.”

Back when we started SV-POW!, Mike predicted that the technical niche blog was the wave of the future. That prediction does seem to be coming true, albeit more slowly than I thought it would. Nevertheless, if you are susceptible to the inherent fascination of rodent teeth, get yourself over to Ian Corfe’s Tetrapod Teeth & Tales for more geeky goodness.

Now, in a move that will possibly enrage one segment of the audience but hopefully delight another, I am going to forge even further away from the ostensible raison d’être of the blog and talk about monsters. Specifically Cthulhu–in my experience, in the Venn diagram of life, the “interested in paleo” and “interested in Lovecraft” circles overlap almost entirely. Over at my everything-except-paleontology-and-astronomy blog, I’ve been thinking about Lovecraftiana and wrestling with what a Cthulhu idol, such as those described in Lovecraft’s stories, ought to look like. If you’d like to contribute, get on over there and leave a comment. If you send* me a picture (drawing, painting, 3D render, photo of sculpture, whatever) or leave a link, I’ll include it in an upcoming post. Cthulhu fhtagn!

* Send to mathew.wedel@gmail.com, please include Cthulhu in the subject line.

Cthulhu sketch 1

I guess pretty much all researchers must suffer from Imposter Syndrome every now and then — the sense of not really belonging, not knowing enough, not getting enough done to justify our position. I particularly remember feeling this after being awarded my Ph.D: the sense that I couldn’t possibly know enough about enough to be worthy of it. Even now, several years down the line, I sometimes look at my papers and think, pfft, there’s nothing to them, anyone could have done that.

I thought of this tonight because of a a tweet I just saw from M. J. Suhonos, Digital Technologies Development Librarian at Ryerson University:

https://twitter.com/mjsuhonos/status/324963845179314177

And the advice I gave in response:

The reason I say this is because a few days ago I did a phone interview for a news piece, and was sort of surprised to find myself talking confidently and fluently, just like someone who knows what he’s talking about. Until I realised that’s what always happens when I do an interview. And that’s because, well, heck, I do know my subject (otherwise why would they even be talking to me?)

And I bet you know your subject, too. You just need to see your own knowledge against the backdrop of what a normal person knows.

Meanwhile, as a contribution to John Conway’s superb “grumpy Hypsilophodon” meme, I give you: this.

grumpy-stinking-hypsilophodon

Living dead girl

Hey, look–dinosaurs!

My spouse, Vicki, the other Dr. Wedel, is a physical and forensic anthropologist. And she’s one of a very small number of scientists who have (a) learned something new about the human body, and (b) used it to help identify dead people. And since that process involves the sciences of hard-tissue histology and skeletochronology–not to mention lots of dead folks–I reckon it might be of interest here. Hence this post.

This started about a decade ago, when Vicki was working on her PhD under Alison Galloway at UC Santa Cruz. Vicki worked with Alison on a ton of forensic cases, including some you probably heard of–they analyzed the remains of Laci Peterson and her unborn baby, Connor, for Scott Peterson’s murder trial. I had the unusual privilege of assisting a couple of times, on other cases, once to take some pictures in the lab while Vicki fished the skeleton out of the bag of skin that was all that was left of the body, and once to crawl around on my hands and knees picking human finger bones out of a muddy slough near Santa Cruz. All in all, I’m happy that my usual victims have been dead a lot longer.

CT reconstruction of skull with bullet holes. Courtesy of the National Library of Medicine

CT reconstruction of skull with bullet holes. Courtesy of the National Library of Medicine

Incidentally, the only show with forensic content that Vicki will watch voluntarily is Dexter. She cannot stand CSI, NCIS, or the other “behind the scenes” forensic investigation shows. We’ve tried watching them, but the inaccuracies drive her crazy (paleo people: imagine getting the Clockwork Orange therapy and being forced to watch Clash of the Dinosaurs). Real cases are solved by teams of specialists, not two omnicompetent protagonists; it takes weeks or months, not half an hour; and if the forensics people carry guns, it’s because they know waaaay too much about how some very bad, very organized people dispose of bodies (the short answer is, not thoroughly enough*).

* Once a guy who was threatening to testify against a certain criminal organization was shot in the head, his body burned, and his burnt remains scattered along the side of the road. Vicki and Alison picked the bone shards out of the roadside gravel, identified some of them as bits of skull, and found bevelling diagnostic of ballistics trauma on some of those. The way the bone had shattered showed that the gunshot had been inflicted perimortem–around the time of death–and before the body was burned. Bottom line, whatever plan you have to get rid of the body, it is probably not going to be enough to keep someone like Vicki from figuring out how you did it. That much, the TV shows do get right.

Skull being cleaned by dermestidbeetle larvae. Image from Wikipedia.

Skull being cleaned by dermestid beetle larvae. Image from Wikipedia.

Not only is hard to really, truly get rid of a human body, it’s also hard to tell exactly when a person died, especially if all you have is a body in the woods. Insects are good–there’s a whole field of forensic entomology, whose practitioners age cadavers based on what insects are present and what stages of their life cycles they’re in. But what if all that is left is a pile of bones in the woods (which happens more often that you might think, and sometimes for completely innocuous reasons)? I’m preaching to the choir here, but bones can survive for a long time, so general wear-and-tear doesn’t tell you much. Rapetosaurus looks like it died last year.

There’s another side to this, which is figuring out how old someone was at the time of death based on their skeleton. Tooth eruption is good, and fusion of the epiphyseal growth plates, but both of those processes are basically done by the time people are in their mid-20s (teeth) to mid-30s (epiphyseal fusion). After that, there are methods based on the morphology of the auricular surface of the ilium and the public symphyses, but these only narrow things down to intervals of 5 to 15 years, and that’s a lot of missing persons reports to sift through. And none of the regular skeletal methods work past the age of 55 or 60. After that, no matter how healthy you are, the primary skeletal changes are attritional (i.e., you’re wearing out), and that process varies so much among individuals and populations that there are basically no predictive guidelines.

All of this was on Vicki’s mind when she was a grad student, so she was alert to anything that might help forensic anthropologists narrow down the possibilities for identifying dead folks. She was teaching in an osteology course and one of her students, Josh Peabody, brought up dental cementum increment analysis (DCIA), which is used in zooarcheology to determine the age and season at death of animal remains found at archaeological sites. Josh wanted to know if the method worked on humans.

Image borrowed from the University of Copenhagen.

Faunal bone from an archaeological dig. Image borrowed from the University of Copenhagen.

At the time–2004–DCIA was being tested for age at death in some historical human populations from archaeological sites, but no-one had tried using it for season at death. So Vicki and Josh set out to see if it would work.

Our teeth, like those of other mammals, are held in their sockets by periodontal ligaments. The periodontal ligament of each tooth attaches via Sharpey’s fibers to the dental cementum on the tooth root(s). Cementum is laid down in annual bands, so you can count the number of bands on a tooth, add the normal age at which that tooth erupts, and get a pretty tight estimate of when the animal died. So much for age at death, which was already being done on humans in a limited way in the early 2000s, albeit in archaeological rather than forensic contexts.

But wait, there’s more. Actually two bands of cementum are laid down every year–a dark band in the winter (roughly October to March) and a light band in the summer (roughly April to September). ‘Dark’ and ‘light’ describe the appearance of the bands under polarized light microscopy. In the summer months, the collagen fibrils that make up the cementum are aligned parallel to the tooth root, so more light comes through. In the winter, the collagen is aligned perpendicular to the root, so less light is transmitted, and the winter bands appear darker by comparison. So not only does the number of pairs of light-and-dark bands tell you the number of years since the tooth erupted, the color of the outermost band tells you in which six-month period the individual died, and the thickness of the outermost band might help you narrow that down even further.

Dental cementum increments in a human tooth, from V. Wedel (2007: figure 1).

Dental cementum increments in a human tooth, from V. Wedel (2007: figure 1).

At least, that’s how it works in other mammals. Would it hold up in humans? After all, we’re pretty good at adjusting our environments to suit us, rather than vice versa. If the winter-summer banding pattern was present in humans, it would be a huge boon to forensic science. Even people in their 40s and beyond with no very reliable skeletal indicators of age could be aged to within a year or two, and their season at death narrowed down to a 2-3 month window.

To find out, Vicki and Josh had a dentist in Santa Cruz collect 112 teeth pulled from patients over the course of a year (with full IRB approval and informed consent from the dental patients). For their purposes, a tooth pulled from a live person is just as good as one from a cadaver or skeleton–extraction kills the tooth as surely as death of the body. Better, even, in that it was easier to quickly get lots of teeth with very precise extraction data.

Vicki and Josh cut a few teeth together and they found dark and light bands right away. They presented those preliminary results at the American Academy of Forensic Sciences meeting in 2005. After that, Josh got busy with his own research, but Vicki pressed on (while finishing a dissertation on different project, and being a first-time mom).

If this was a movie, this is the part where there would be a montage of inspirational music to get us quickly past a lot of hard, boring work. Each of the 112 teeth had to be embedded in plastic, a section through the root cut out with a saw, that section mounted on a slide and ground down until it was translucent (this process will be familiar to bone histologists of all stripes, paleo or neo). Then Vicki had to go all the way around the perimeter of the each root to find the place where the cementum bands showed the most clearly, and count them. This part is trickier than it sounds, unless you’ve done some histo and know just how butt-ugly some sections can be under the scope.

The results? In the words of the Bloodhound Gang, which Vicki quotes in her DCIA talks, “You and me baby ain’t nothin’ but mammals”. Here’s the payoff graph:

Percent completion of outer cementum increment by month, from V. Wedel (2007: figure 4).

Percent completion of outer cementum increment by month, from V. Wedel (2007: figure 4).

The one out-of-place measurement was probably caused by the dark band not being thick enough to register clearly on the image.

Now that she knew that DCIA could be used to determine season at death in humans, Vicki started applying it in her forensic cases, of which there have been many. The vast majority of the work of forensic anthropologists is invisible to the public: after analyzing a set of remains, a forensic anthropologist writes a case report for whatever law enforcement office (or, much less frequently, law firm or other entity) brought them in, and that’s that. The case reports are almost always confidential, but they have to be written to exacting standards since they may be used as evidence in court. So forensic anthropologists spend a lot of time toiling over papers that hardly anyone gets to read.

However, sometimes a case is written up for journal publication–if it’s sufficiently novel or unusual, and if permission can be secured from all of the relevant parties. In 2008, Vicki was approached by the Merced County sheriff’s office to help try to identify the remains of a young woman who had been murdered in 1971. That’s the 37-year-old cold case mentioned in the title of this post, and rather than tell you about it, I’ll point you to Vicki’s case report (Wedel et al. 2013), published last month in the Journal of Forensic Identification and freely available here.

Vicki with the exhumed skeleton of Jane Doe. Photo by Debbie Noda of the Modesto Bee.

Vicki with the exhumed skeleton of Jane Doe. Photo by Debbie Noda of the Modesto Bee.

I wasn’t sure whether to post about this or not–as cool as they are, murder cases are not our normal stock in trade on this blog. What decided me was talking with Andy Farke. He read Vicki’s paper as soon as it came out, and he said that he really enjoyed getting to see how forensic anthropologists work in the real world. I sometimes take for granted that, since I am married to a forensic anthropologist, I get to see how this works all the time. But that’s a pretty rare experience–if paleontology is a small field, forensic anthropology is positively tiny. So if you want to see an example of the real science that CSI and the like are based on, here’s your window.

What’s next? Vicki has several validation studies on DCIA in progress, for which she and her collaborators have collected a much larger sample size–over 1000 teeth–to try to answer questions like: what tooth is best to use for DCIA? Should the histological sections be made longitudinally or transversely through the tooth root? Does cementum banding vary with latitude? And since banding patterns are reversed in the Southern Hemisphere, following the flip-flopped season, what happens at the equator? Watch this space, and keep an eye out for Vicki’s future publications–including a book due out next year–at her website, Bodies, Bugs, and Bones.

References

Folks, I just got this email from open-access guru Peter Suber (quoted with permission):

I get ominous warnings when I try to visit your blog at https://svpow.com/. The warning in the browser says, “Malicious website blocked”. The warning in a separate pop-up says, “The Web page you are attempting to visit…could potentially harm your computer.”

Both warnings are from Trend Micro, which came factory installed on my Windows-based Dell laptop. I’ve found it reliable in the past.

Has anyone else seen this? Is it something we should be worried about? Does anyone know what we can do to stop it?

(BTW., for what it’s worth I can assure anyone else who’s seeing this warning that it can be ignored. There’s no malware here.)

 

Always two there are…

October 31, 2011

…a master and an apprentice.

Here’s how the Wedel Lab rolls on Halloween:

Check out that padawan braid. It’s official, I have the world’s coolest grad student. Although Vanessa’s choice of lightsaber is a bit worrying. Great danger I foresee in her training.

(This is sort of a riff on the recent post, Tutorial 12: How to find problems to work on, which you might want to read first if you haven’t already.)

Something that has been much on my mind lately is the idea that if you don’t go too far, you don’t know how far you should have gone.

I first encountered this idea in a quote from concept artist Ian McCraig, in The Art of Star Wars: Episode I (p. 195):

People ask when I know when to stop scribbling, and decide a work is finished. I say you have to go too far and destroy it, because then you know when you should have stopped and can go back. If you don’t, you leave untold riches out there.

I’m sure McCraig wasn’t the first to formulate the idea, he’s just the medium through which I first learned of it, back in 1999.

Scott Aaronson calls brief statements of this sort “Umeshisms“, after his advisor, Umesh Varizani, who said,

If you’ve never missed a flight, you’re spending too much time in airports.

A follow-up post, reporting the results of an Umeshism contest among his readers, also has some gems.

For the sake of completeness, I should note the very economical general formulation of this idea from Tagore Smith, in a comment on Mike’s blog that Mike later promoted into a stand-alone post (the comment, not this excerpt):

I haven’t gone too far yet so I am not sure if I have gone far enough.

Here’s the larger lesson Aaronson drew from his advisor’s airport quip:

In a single sentence, Umesh was communicating an entire philosophy of life: concentrate on the high-order bits. The squash player who runs back and forth to attempt every shot, the student who’s never late with an assignment, the researcher who stalks an unimportant problem like Captain Ahab: all have succumbed to the tyranny of the low-order bit. They need to realize that, as in a randomized algorithm, occasional failures are the inevitable byproduct of a successful strategy. If you always win, then you’re probably doing something wrong.

One of the reasons this is so much on my mind is that I did an editing pass on a manuscript Mike is working on, and he took some of my suggestions, but not all of them. And I realized that that is probably a good thing; if he’d taken all of my suggestions, it would mean that I not edited hard enough. And it occurred to me that the Umeshism philosophy can probably be more effectively implemented by two people than by one. One can’t be an iconoclast all the time and still be productive; you have to settle down sometime. Also, two sets of eyes are going to see more ways to push the edge of the envelope.

“The researcher who stalks an unimportant problem like Captain Ahab” is also worth thinking about–specifically, to wonder which among my many concurrently developing projects are high-order bits, and which are not. Mike and I refer to our lists of works-in-progress as POOP, or Prioritized Ordering Of Projects, but we (or at least I) tend to slip into using “priority” to mean, “what am I working on next”, and not, “what should I be working on next”. I have let many projects slip into limbo while pursuing others, and it would be worthwhile to periodically reassess whether I’ve let the right ones slip. I strongly suspect that it has not always been the case. I just wrote in Tutorial 12 that any productive researcher is going to die with a mountain of intended work left undone. It is probably not too early for any of us to look at our array of projects and ask, “Which among these most needs rescuing from that mountain?”

The long Aaronson quote above also raises the specter of the costs of catching mistakes, which Paul Graham and Mike have both written essays about. Both basically boil down to “safety is expensive”. And that is sort of what I meant in Tutorial 12 when I wrote, “If you’re not feeling stupid, you’re too comfortable, and it might be time to do an audit and see if you’re actually contributing to science at all.” Feeling stupid–in the scientifically productive way–is a symptom of being out of your safety zone, where you are more likely to learn valuable things and have new ideas. I also argued that you have to sift through a lot of facts and ideas to hit on the handful that might meaningfully become part of your research. Most of the stuff you encounter will not be relevant to whatever it is you’re trying to do, but that’s okay. If all of your ideas seem like good ones, either you’re playing it very safe (and therefore the ideas aren’t actually that good), or you’re having delusions of grandeur.

I remember seeing somewhere–irritatingly, at this point I have no idea where–some guy arguing, maybe half-seriously, that any project was plagued both by errors that one knows about and also by other errors or biases of which we are ignorant, and that therefore he always tried to make sure that his known errors were bigger, because that way he was in control (the original was more cleverly and economically phrased).

All of this interests me, because so many forces in our lives conspire to make us afraid of making mistakes, and often even more afraid of admitting to them once they’ve been made. But we all make mistakes, all the time. So what are we going to do about it?

Right now my Gmail sig quote is a line from Clay Shirky:

To put yourself forward as someone good enough to do interesting things is, by definition, to expose yourself to all kinds of negative judgments, and as far as I can tell, the fact that other people get to decide what they think of your behavior leaves only two strategies for not suffering from those judgments: not doing anything, or not caring about the reaction.

The hardest reaction to not care about is your own. Doing good work demands the capacity to take mistakes in stride and keep moving forward. Doing great work might require another level of perspective, in which some kinds of mistakes are just indicators that you’re on the right path.

Just noticed this over on ScienceBlogs:

Tetrapod Zoology conquers the world!

SV-POW!sketeer Darren’s Naish’s other blog Tetrapod Zoology has — rightly — often featured strongly in the Readers’ Picks sidebar; but this is the first time I’ve seen it, or indeed any blog, completely monopolise the list.

ScienceBlogs has other blogs that get more hits and more comments than Tet Zoo — mostly because they consist of flamebait — but when you want solid chunks of meaty, scientific nourishment, Tet Zoo now seems to be pretty well established as king of the hill.  On the slight chance that any SV-POW! readers aren’t already regulars at Tet Zoo, let me recommend it in the strongest terms: I know of no other blog that does such a good job of presenting hardcore science in a readable, approachable manner.

So congratulations to Darren, and long may it continue!