The Museum That Changes

There is a beautiful image in Richard Dawkins’s Climbing Mount Improbable.

Imagine a museum containing every possible shell.

Not every shell that has ever existed. Not merely every shell that evolution might one day produce. Every form of shell that can be generated within the dimensions of variation we have chosen to describe.

The museum extends in all directions. Each dimension corresponds to some feature of form: curvature, aperture, coiling, thickness, ornamentation. Walk in one direction and the shells become longer; in another, more tightly coiled; somewhere else, the aperture changes shape. There are galleries upon galleries of forms.

And most of them are empty.

Dawkins’s point is not simply that nature has produced many extraordinary forms. It is that the forms we actually encounter occupy only a tiny region of a much larger space of conceivable forms.

Evolution, in this picture, is a journey through the museum.

It does not visit every gallery. It follows particular paths, constrained by developmental possibilities, inherited structures, environmental conditions and the contingencies of history. The shells we find are not scattered randomly throughout the museum. They form trajectories.

It is a wonderful image.

It also connects to two even more wonderful images.

Borges imagined a Library containing every possible book that could be constructed from a finite alphabet. Dennett, extending the idea into biology, imagined a Library of Mendel containing the possible genomes. Dawkins gives the abstraction a visible form: instead of all possible books or genomes, we can walk among all possible shells.

There is something intoxicating about such a place.

For a moment, possibility seems almost tangible.

One can imagine wandering through the galleries and seeing forms that no organism has ever inhabited, alongside forms that have appeared repeatedly in the history of life. Evolution becomes a kind of exploration: a movement through a pre-existing abundance of possibilities.

And yet there is a small difficulty.

It is not really a difficulty with the museum.

It is a difficulty with the walls.

For what determines the shape of the museum?

We have specified dimensions of variation. We have specified what counts as a shell. We have specified the rules by which one form can differ from another. Given those specifications, we can construct a space of possible forms.

That is perfectly legitimate.

Indeed, it is extraordinarily useful.

But perhaps we have quietly moved from saying:

Here is a space of possibilities generated by these rules

to imagining:

Here is the space of everything that could possibly exist.

Those are not quite the same thing.

A space of possibilities is always a space relative to something.

The Museum of All Shells is generated by a particular way of describing shells. The Library of Mendel is generated by a particular conception of genomes and their possible combinations. Borges’s library depends upon its alphabet, its format and its rules of combination.

Change the rules, and the museum changes.

This becomes more interesting when we return to evolution.

Perhaps evolution is not simply a matter of organisms wandering through a museum whose architecture was already there.

Perhaps, occasionally, something happens that changes the relations from which the museum itself is constructed.

A new developmental pathway can alter what forms are accessible. A new organism can transform an ecological relation. A new ecological relation can make other forms viable. A change in one participant can alter the conditions under which another participant can exist.

The history of becoming can therefore change the conditions of further becoming.

And now the museum begins to look rather different.

Instead of one enormous building containing every possible form, perhaps there is a succession of museums.

A possibility becomes actual.

The actualisation changes the relations among things.

Those changed relations make some possibilities more available and others less so.

And so a new museum begins to take shape.

Museum₁ → becoming → transformed relations → Museum₂ → becoming → transformed relations → Museum₃

The point is not that the old museum disappears. Much of its architecture may remain. Existing possibilities can persist. Old forms can continue to recur. But the structure of what can happen next is no longer exactly what it was.

The museum has acquired a history.

This also changes how we should think about the empty galleries.

An empty gallery need not represent something that nature has simply failed to discover.

Perhaps the form is unavailable under the relations that currently obtain.

Perhaps another relation would make it accessible.

And perhaps some possibilities that once existed can disappear when the relations that sustained them disappear.

Possibility, then, is not merely a matter of how many forms can be imagined.

It is also a matter of what the world currently makes possible.

That distinction is subtle, because a model can still be enormously valuable. We can still draw the museum. We can still map its dimensions. We can still ask why evolution has occupied one region rather than another.

Indeed, those questions become more interesting once we recognise what the map is doing.

The map gives us a space of model-relative possibility.

History gives us something else.

History changes the relations within which possibilities become available.

And this means that becoming is not merely a movement through possibility.

Sometimes, becoming changes possibility itself.

The shell that appears on the museum floor is not simply a destination reached by a wandering evolutionary process. Its appearance may alter the relations that determine where the next corridors can lead.

The traveller has become part of the architecture.

Perhaps that is why the Museum of All Shells is such a beautiful image after all.

We need not abandon it.

We only need to imagine that, somewhere behind the curator’s desk, there is a rather mysterious workman carrying a hammer.

He is not adding new shells to the collection.

He is knocking through walls.

And when we return tomorrow, there may be a corridor where yesterday there was none.

The museum does not merely contain the history.

The history changes the museum.