Monday, July 26, 2010

The F-Word

Last week a colleague sent me a link to an article in the Chronicle of Higher Education. "You might find this interesting," her accompanying email said, teasingly. Like a fool, I clicked on the link. Ugh. It ended up that, with one thing or another, I had a week eaten dealing with various issues surrounding this article, which in the end boiled down to this blog post on the subject of fakes.

Long-time readers of this blog may recall Thomas Benton from a post last year regarding another Chronicle article, in which this professor English from Hope College MI modestly set out to save natural history museums from themselves. As I said at the time, his piece was the typical curate's egg that results when an intelligent, but basically uninformed writer tackles a subject with which they have a passing familiarity - there was much that was good, some that was misguided but interesting, and a fair amount that was downright wrong. I took a few cheap shots at the article and then thought no more of it. Now comes another piece and this one, I'm afraid, demands a more robust response.

The thesis of the lastest article is that natural history museums have got into the business of exhibiting "fakes." Fake, with its implication of conscious decption, is an inflammatory word to direct at any museum display, but especially ones in the sciences where we pride ourselves on adhering to vigorous standards of scientific objectivity. It is also an accusation more likely to be hurled at us by creationists and other people of an anti-evolutionary bent than by the likes of Benton, who professes to like natural history. So what gives?

When Benton refers to fakes, he's actually talking about casts - specifically the cast dinosaur skeletons that many museums exhibit in their galleries. He strongly believes that museums should display "the real thing;" to do less than this is to smash the dreams of the innocent child who asks that most common of museum questions, "is it real?" If you say "yes," you are engaging in deception; if you say "no," the child is disillusioned and an inspirational moment has been lost. To which I say humbug, or words to that effect.

Before delving into why this is a fallacious argument, I think we need to understand why museums display casts. First of all, it's important to realize that complete skeletons of dinosaurs are incredibly rare. In fact, I'm going to hazard a guess and say that there is no 100% intact skeleton of a dinosaur on display anywhere in the world today, by which I mean a skeleton in which there are no bones missing and in which every bone is complete and undamaged.

The process by which a fossil forms is highly susceptible to the vagaries of chance. As the animal's carcass rots, it may fall apart, or be pulled apart by scavengers. It might be swept away by a river or flood, and its bones scattered over a vast area. Only part of it may be buried in mud and preservered; the rest gets broken up and decays. And then, assuming that it is preserved, some of the bones may be exposed and weathered away before the fossil is discovered and excavated. The upshot is that most of the fossil animals in museum collections are far from complete.

How incomplete are they? Well, for illustration let's take a look at that most famous of dinosaurs Tyrannosaurus rex. The picture at the top of the page was produced by a former colleague of mine at AMNH, Benjamin Burger, for a long-departed web page on the history of T. rex. It shows the seven specimens of this dinosaur in the AMNH collections. The bits in the red are the fossil bones, shown on outlines of the skeleton; in other words, the bits that actually exist. Not very much, is it? In fact, of all the specimens of this dinosaur that have been discovered since it was first named in 1905, only three have more than 50% of the bones present, and the most complete (the famous "Sue" at the Field Museum) is still missing around about a quarter of the bones of its skeleton.

By now, those of you who have visited the fourth floor fossil halls at AMNH are digging back in their memories and wondering how it could be that they saw a complete, articulated specimen of T. rex. The answer, of course, is that they didn't. What they saw is a composite skeleton, which contains a mixture of real fossil bones, and resin casts taken from other fossils. The skull of this specimen is too heavy to be displayed on the mount, so it has been replaced by a resin cast. The real skull is on display in a glass case alongside it. All of this is explained in the labels that accompany the skeleton.

This is an important ethical point. Generally speaking, it's considered to be OK to display composites and casts, provided that you make it clear what is fossil bone and what is resin or plaster. Today we do this by a mixture of label copy and by using materials that are a slightly different color and texture to the bone, so that it's obvious to the visitor what is bone and what isn't. We also try to avoid doing things like mixing and matching bones from different individuals, so you don't end up with a left leg from one animal and a right leg from another.

Back in the golden age of paleontology, of course, they were a good deal less fussy. The Peabody Museum's skeleton of Stegosaurus, for example, contains bones from at least five different individuals (which are listed on the label accompanying the skeleton). The bones in our skeleton of Apatosaurus come from a single individual, but are padded out with a large amount of plaster, most of which was colored to blend in with the real bone. As a result we have no idea how much of the skeleton is bone and how much is restoration. One of the interesting things about our proposed overhaul of the fossil galleries is that we are intending to disarticulate and remount the skeleton, at which point we will finally know the answer to this question.

Another famous example of composite skeletons are the various dodos scattered around the world's museums. Not one of these represents a single animal - they were, for the most part, reconstructed from thousands of jumbled bones that were excavated from the Mare aux Songes, a marsh on the island of Mauritius. The closest thing to a complete skeleton from one individual is the head and foot on display in the Oxford University Museum of Natural History - in that case we know that they are part of one animal because it was brought back from Mauritius alive in the 17th Century.

Of course, many museums don't even have partial skeletons of dinosaurs, so they choose to display cast skeletons. Casts are made from the original fossil bones present in museum collections - it's an exacting job which takes highly skilled workers and there are very few companies in the world that can do it. The end result is a precise reproduction of the original specimen - as close to the fossil as its possible to get without actually owning it. Casts are heavily used in paleontology because of the scarcity of fossil specimens - they are exchanged between museums and sent out on loan to researchers. We assign them catalog numbers and treat them in the same way as we would treat any museum specimen.

Casts are real, in the sense that they could not exist if there was not also a real specimen somewhere. Of course, there are anomalies. Modern technology makes it possible, for example, to digitally scan the right femur from a dinosaur, mirror it, and use the data to produce a cast of a left femur that has never actually existed. Is this ethical? I would say yes, provided the process is made clear to the visitor in the exhibit label. As long as you do this, the specimen cannot be labelled as fake.

All of this has demonstrated (I hope) that 1) fossils are incredibly rare, 2) complete fossil skeletons are almost non-existent, 3) to counter this, museums have a long history of reproducing fossils for research and display, and 4) there are a series of ethical safeguards employed to make certain that visitors are aware of this. Complaining about the presence of casts in museum displays is a little like complaining about photographs in a book on the Grand Canyon - yes, they are a poor substitute for actually visiting the Canyon, but if you can't do that then photographs serve an important purpose.

Casts are much more impressive than photos. They convey a sense of the sheer scale of these long-extinct animals in a way that no photograph or film can ever do. I can still remember, as a child, the sense of awe engendered by seeing the massive skeleton of Diplodocus at the Natural History Museum in South Kensington, London. My youthful wonder was not at all diminished by knowing that it was actually a cast of a specimen from the Carnegie Museum. Was it “real?” Absolutely, in the sense that there was once an animal that looked like this, we have the bones to prove it, and this exhibit specimen could not have been made without those bones.

Ultimately what we're trying to do in museums is to generate that feeling of awe; to find the best possible ways to inspire people with a sense of wonder at the natural world and the evolutionary processes that underpin it. To equate this with the antics of P.T Barnum and throw accusations of fakery at us does no-one any favors.

3 comments:

  1. There are of course also other reasons you don't mention for displaying casts (I assume simply to focus on one main point): displaying a cast means the actual specimen remains available for study, casts are considerably lighter than actual specimens so are logistically easier to handle, etc.

    A very nice post, I have to say.

    ReplyDelete
  2. In my heart, I sympathize with those who want to see the real fossils rather than casts. However, that is not always the best way to serve science. The Carneigie NHM had to take down many of it's real bones because they were being eaten away by acids or moisture or something in the air. They were literally turning to dust. Of what scientific value is a crumbling specimen? As you know, many skeletons are unique in that they show specific morphologies, like the injuries to "Big Al," or "Sue". Some bones, like an Alioramus skull may be one of only four ever found. Even a skull from a plentiful species, like Triceratops may be important because it represents part of a series of growth stages (Torosaurus/Triceratops argument). I love to see real bones, but not if it means risking future research. Nothing ends an argument between researchers like a trip to see the real bones.
    Also, cast offer a museum a chance to show visitors a range of fossils they might not ever see otherwise. I am probably not ever going to be able to afford to go to China or Argentina to see certain specimens, and for some species (Giganotosaurus), there are not enough real skeletons around for many museums to have one yet. Travelling exhibits offer one solution to both problems, so that the real specimens can be seen outside their home countries, but space and money considerations make some of those hard to do.

    ReplyDelete
  3. Excellent post. I had a discussion with a friend about this in the newly revamped Royal Ontario Museum.

    Since the renovation, they've put colour-coded illustrations on their placards showing how much of the fossil on display is real material. A friend was disappointed. I welcome the change: it's more honest, and leads to a better understanding of how precious fossils actually are.

    As you say, there aren't any complete ones.

    (H/t to Michael Barton for sharing this blog post via Google Reader.

    ReplyDelete