Open access and fossil reconstruction

I would love to be able to say that the Ardipithecus pelvic and cranial reconstructions were open access.

The reconstruction of fragmentary fossils has in the past been more of an art than a science. An anatomical expert can eliminate some possible morphological configurations based on the remains themselves. But for many, she has only her knowledge of variation in extant species as a reference. The bones she has studied might or might not be representative of anatomical variations; variations within extant taxa might or might not be relevant to ancient species. Working with casts of a fragile specimen is fraught with problems. Missing parts or uncertain joins in the fossil material can be shored up with plasticine, but to other scientists these This process poses obvious drawbacks: the resulting reconstruction may present the appearance of features that are in fact completely sculpted out of clay.

I describe this as an “art” for one important reason: there are many barriers to replicating a reconstruction. The reconstruction ends up including the quirks of other specimens used as reference material, may have fragments misplaced due to uncertain identifications.

The pelvic reconstruction of Sts 14 is one example of how the implicit assumptions of a reconstruction can affect the interpretation of a fossil. After its discovery in 1947, John Robinson reconstructed the distorted ox coxae and partial sacrum with a rounded pelvic inlet, more or less like humans. After the discovery of Lucy’s pelvis (AL 288-1), it was clear that A. afarensis had a very broad pelvis, flattened from front to back — different from Sts 14’s apparently rounded pelvic shape. The original reconstruction of Sts 14 was revisited in the 1990’s, when it was found that a flatter, more Lucy-like shape is consistent with the specimen’s anatomy (Abitbol1995). The point is not that Robinson’s reconstruction was wrong — any reconstruction will be wrong in some details. Nor is the point that the reconstruction was not replicable in principle – at any time, anybody could have sawn apart a few casts of Sts 14 into the component bones, and then built them back in a different shape. The point is that replicating the reconstruction would have been expensive and difficult, so for forty years nobody made the effort.

With digital scanning, all the expense and difficulty go into producing the initial scans. After that, the only limit on testing a model reconstruction is the time that someone is willing to spend studying the anatomy.

In principle, this is wonderful. A whole team of researchers can easily share digital models, working on the specimen with an explicitly shared referent. The digital model can be instantly transported anywhere in the world, allowing direct comparisons with original material housed in museums. The existence of such virtual 3-d images of fossil and model allows independent scholars to apply their own models, testing a model’s assumptions without needing to handle and possibly damage the original specimens.

But many of these benefits of the technology depend on scholars being able to access the scans. Today they can’t.

I’m hopeful that in the future we’ll be able to make full use of the technology — not only enabling a single reconstruction, but multiple reconstructions and widespread comparison of digital models.