Thursday, February 4, 2010

The Decline of Documentation

I'm a huge fan of Matt Wedel's "Measure Your Damned Dinosaur" philosophy. For those of you who aren't familiar with his post on the topic (and seriously, it's probably one of the best pieces of research blogging from 2009), the title is pretty self-explanatory. Despite scads of new techniques, a bloatload of journal options, and the rise of endless supplementary data files, we paleontologists just ain't doing our job anymore when it comes to publishing measurements of specimens. As Wedel said,
"It blows my damn mind that a century ago people like Charles Whitney Gilmore and John Bell Hatcher could measure a dinosaur to within an inch of its life, and publish all of those measurements in their descriptions, and lots of folks did this and it was just part of being a competent scientist and doing your damn job. And here we are in the 21st century with CT machines, laser surface scanners, ion reflux pronabulators and the like, and using a narf-blappin’ TAPE MEASURE is apparently a lost art."
Just for giggles, I decided to find out if things really were better in the past, or if we're just waxing nostalgic for a golden age of documentation that never existed. Being someone who is number-inclined, I grabbed a bunch of ornithischian data from The Open Dinosaur Project. Using some handy-dandy spreadsheet functions, I extracted data for the year of publication for a series of measurements as well as the number of relevant limb bone measurements for that paper that made it into our database.

Then, it was time to run statistics! I wanted to see if there was a correlation between year of publication for a specimen's measurement and the number of measurements published for each specimen. So, I ran a non-parametric test of correlation (Spearman's rho, or ρ). Care to guess what I found?

Sadly, Wedel is right. There is a negative correlation between year of publication and number of measurements: ρ = -0.44, P less than 0.0001.

So then I thought, there are a lot of papers that have just published a single measurement of an isolated bone, or a whole table of single element specimen measurements (e.g., femur length for 20 different species). Maybe that was biasing the dataset. Thus, I trimmed out all of the entries that had only one measurement. Still, there was a significant negative correlation (ρ = -0.27, P less than 0.0001). The average paper published between 1920 and 1930 had 18.5 measurements; between 2000 and 2009, 14 measurements.

Have our dinosaur skeletons gotten less complete? Or have we given in to the need to squeeze less information in less space, and perhaps a little laziness on the side? What will it take to change this trend? It's all food for thought.

Caveat: This is a highly unscientific, probably very non-random sample. Oh well.

10 comments:

Mike Taylor said...

Andy -- show us the graph!

And this should be included in the Discussion section of the initial ODP paper in PLoS. It's an important and relevant observation.

Zhijie (Jack) said...

Measuring was the one of the first things I learned to do! Maybe a periodic refresher in "basic training" is required for some people...

220mya said...

I think there are many factors causing the decline in published measurements. Possibly one of them is that size in and of itself has become less important for taxonomic and systematic arguments. Size alone is no longer a valid criterion for separating taxa, although it used to be. That said I also think the reasons you brought up had just as much of an effect. None of this though justifies the decline - measurement data are still very valuable and a basic thing to report.

Anonymous said...

I think the decline in measurements is because many researchers do think it "old school," and, coupled with the rise of cladistics, I think morphometric data got short-changed. I suspect that will change -- what good is a phylogeny if you can't use it for something like morphometric comparisons among related taxa, etc.

And I point out I like cladistics and think its a good tool.

Matthew said...

Anonymous is Matthew Bonnan -- I guess I don't know how to blog. =)

Schwarzkophf said...

Nice article ..
Very interesting!

Heinrich said...

nice to see a gut feeling confirmed. not so nice that it is this specific gut feeling :(

I guess many people feel that numbers are boring, useless (how many badly measured dinosaurs have I seen? 20? at least...), do not tell us anything about important issues like ecology and evo-devo, and besides, it takes TIME to take them, write them down, correct all the screw-ups. Much like detailed lists of material: too often I read '...a partial skeleton including a complete left leg, parts of the tail and a right humerus'. HELLO? What exactly have you losers found????? And what is NOT in your list? Ah, I see, it is not important, you can't be bothered to type the names of 17 bones.

That also applies to measurements - and here comes my confession: I did not include any measurements in my submitted and accepted papers on Plateosaurus. For a very simple reason: it is a bother to measure, and I can supply high res digital files of the beast. You want measurements? Well, just email me, and you can take exactly those measurements you want yourself. No need to trust me, no need to deal with my typos, no need to deal with differences in how distances are defined. 'Max length' is what you want it to be, 'min diameter' is in the place you want it to be. And that, I think, is the minimum we all should do: if we do not measure and publish, at least enable others to measure for free (i.e. at their own computer). Make you CT scan or laser scan or whatever data available!

Astaga life style on the net said...

what is ornithischian data?
do you have any photos..?

umuts said...

thank you

Beth said...

Measuring dinosaurs can be done through a laser scanning device. I am an artist and I discovered that I can have a perfect impression of a thing by using a 3D laser scanning equipment. Since then, I keep looking for Faro arm for sale and a laser scanning equipment in order to perform my measuring tasks.