Sunday, June 13, 2010

Pathfinding Our Exhibit

Most museum paleontology galleries follow one of three well-trodden themes. These are:

1) A Walk Through Time. The layout of the gallery follows the progression of geological time. I am in the Carboniferous – here is a big dragonfly and a fern; I am in the Cretaceous – here is Triceratops, here is a flowering plant; etc.

2) A Climb Through the Tree of Life. The layout of the gallery reflects phylogenetics. This is typified by the fossil galleries of AMNH, a cathedral to cladistics complete with Stations of the Cross for the synapomorphies of each of the major vertebrate clades (Behold – Epitheria!).

3) What’s in My Backyard? The gallery is arranged according to regional geology, with examples of fossils from each of the major deposits.

In planning the new fossil halls at the Peabody, one of the first questions that had to be considered is which, if any, of these approaches we’re going to adopt. Option 3 can be discarded fairly quickly as – with apologies to all of you passionate Connecticut fossil hounds – the prospect of a gallery featuring Triassic fish and some dinosaur footprints didn’t exactly set the heart pounding. A case on local fossils is one thing, but a whole gallery just won’t fly.

A phylogenetics-based approach has a lot to commend it, especially given the research interests of our curatorial staff, but unfortunately we have a near neighbor in NYC who has already done this, and no-one can accuse us of being copycats.

That leaves a Walk Through Time, which is more or less what the current galleries are. It’s certainly the theme of the two Zallinger murals, which form a great procession of life spanning 400 million years from the Devonian to the Pleistocene. This was the approach taken by all the “prehistoric life” books that I devoured as a kid and one that the public is familiar with.

The problem is that it’s also a straightjacket. It makes it very easy to divide the history of life on earth up into little geological nuggets, each with its own set of bullet-pointed characters. It is the Pleistocene. There are ice ages. It is cold, except during interglacials, when it is warm. There are mammoths and sabertooth tigers. Then humans evolve and kill them all. That is the end of prehistory. Next, agriculture and pyramids.

It’s easy to absorb factoids like this, but cutting things up into chunks dictated by the geological timescale tends to obscure long-term changes that take place over even greater timescales and also makes people think that there are neat divisions between one period and another. One of the nice things about Zallinger’s murals is that by and large they don’t fall into this trap. Stand back and take a look at the Age of Mammals, and you can see that the climate is changing, but by-and-large, the different environments blend smoothly into each other (with the exception of the river that, like some Paleo-Styx, divides Zallinger’s Oligocene parklands from the brown prairies of the Miocene).

This is important, because the message that we’d like to get across through these displays is the dynamic nature of the Earth. The environment is constantly changing, driven by factors such as plate tectonics, mountain building, the movement of ocean currents, and the opening and closing of the oceans themselves. These changes are reflected in the evolution of the organisms living on the planet. It’s a much more fluid situation than the “ladder” of geological time suggests.

This is why, in the end, it was decided to take a “fourth way” in designing the new halls. The layout of the galleries will reflect the changing environment. It’s an attractive option for us, in that much of the research work undertaken by Peabody’s departmental partners over the last decade or so has emphasized interdisciplinary approaches, which have combined environmental sciences, evolutionary biology, and earth sciences. You can see this most vividly in the research programs of the Yale Institute for Biospheric Studies, to which many of the Peabody’s curatorial staff contribute.

By now, some of you are probably asking, how does this differ from a Walk Through Time, in that they are both progressive and have a time axis. The differences are, I will admit, subtle ones, and the best way to explain them will be to look in detail at the planning process for one of the galleries, the Fossil Mammal Hall. Which we’ll do in a future post.

[Extract from "The Age of Mammals" is © 1966, 1975, 1989, 1991, 2000 Peabody Museum of Natural History, Yale University, New Haven, Connecticut, USA; All rights reserved.]

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