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There's now a "How to Evolve" Instructable

I've now posted an instructable that explains how to evolve a balloon animal.

How to evolve a balloon animal

Evolve a unique genetic code by playing a word game, then learn to twist the balloon animal that your genetic code describes! Over 200 kids at World Maker Faire NY 2012 participated in this hands-on activity that introduces the concepts of genotype/phenotype mapping and mutation.

Materials:

• paper and pencil
• a #160 balloon (#160 balloons are nominally 1" diameter and 60" long when inflated)
• a small-diameter pump suitable for inflating #160 balloons

Sources: Qualatex makes reliable #160 twisting balloons and a suitable pump (the #47512 pocket pump.) You can find them sold online.

The Word Game

The game starts on an empty page and proceeds to generate a new word through a sequence of insertions and edits. At each stage in the word's development it encodes a real balloon animal—one you may opt to twist later. In this sense your word's development traces an evolution.

First Rule:
You can insert ud or np anywhere.

On the first line of your empty page, write either ud or np. It's your choice. (We'll always use lowercase letters because the shape of the letters will become important.)

OK, let's apply the same rule again. There is now a choice of three sites at which to make an insertion: at the beginning, between the two letters, or at the end. Mark with an editor's caret the site where you choose to make an insertion. Above the caret, in small letters, write your choice of what to insert, ud or np. Rewrite a clean copy, including the insertion, on the next line.

We now have even more sites for insertion, but let's hold off applying rule one again and see if you have a chance to apply the second rule.

Definition: according to the direction of their strokes, there are two kinds of letters: the up letters, u and d; and the down letters, n and p.

Second Rule:
An up letter can shuffle past a down letter.

Putting it another way: if an up letter is right next to a down letter (in either order) they can trade places. See if your word has an up letter right next to a down letter. If it does, you may opt to invoke the second rule. As an editor's mark, make a tie connecting the two letters you will be switching. Rewrite a clean copy, including the transposition of the two letters, on the line below.

(Both of these rules can be made reversible. The first rule is reversible if we also allow ud or np to be deleted anywhere we find them. The second rule reverses itself whenever it is applied a second time to the same letters.)

Play the word game as long as you like. Make as long a word as you like.

Now, make a clean copy of your word at the stage in its evolution when it is just four letters long. That's an ample length for your first attempt at balloon twisting.

Read Your Genotype

Turn your four-letter word 90 degrees counter-clockwise so that you are reading it from the bottom up. Notice that there are fundamentally two shapes of letters: open letters (u and n), and closed letters (d and p). We'll say that open letters throw something, and closed letters catch something. Also, some letters have strokes that point to the left (u and d), and some letters have strokes that point to the right (n and p).

Scrutinize the shapes of your letters. Try reading them out loud, from bottom up, using the terms throw/catch and left/right. For example undp reads, "Throw left, throw right, catch left, catch right."

Now you're ready to twist.

Twist Your Phenotype

Insert the pump in the nozzle of a #160 balloon and inflate it until there is only about one inch (3 cm) of balloon left un-inflated at the end. (That will leave space for the air displaced by twisting.)

Squeeze the nozzle of the balloon to prevent its deflation; remove it from the pump; stretch it; tie it in an overhand knot; and pull it tight.

By "twisting" a balloon, we really mean, "pinch—then twist." The pinch accurately locates where the balloon will twist. We are going to aim at twisting balloons in consistent  three-inch (8 cm) segments that we will call links. Discover a part of your hand that is three inches wide and refer back to it frequently as a reference when making your pinches. Consistently twisting three-inch links allows you to twist the phenotype of a 6-letter word from a single #160 balloon.

Pinch at a place 3 inches from the knot of your balloon, then twist the balloon about a full turn. (It is natural to fear the balloon will pop while twisting, but this is quite rare.)

Try letting go of the balloon now and you will discover a problem. Until the twisting reaches a certain state (coinciding with the completion of a letter) it is prone to untwist if not continuously grasped. To grasp multiple links it is convenient to fan-fold them in your hand as they are completed. If there is too much balloon for your hand to hold, use your chest to help. (Each time you complete a letter, you can let go.)

Your first letter is always an open one. To make an open letter, twist off three links, then twist the last two links together around their common base. This creates a doubled link. It is these doubled links that we imagine the open letters "throw" and the closed letters "catch."

Between letters, take time to organize your balloon so that the "left" and "right" throw of each open letter is correctly oriented. You will find that the doubled links rather obligingly move to the correct side when pushed.

The "catch" indicated by a closed letter is made by twisting a single link and threading it through the nearest doubled link on the specified side. After threading through, force the neck of the link up against the outer neck of the doubled link—it will snap into place right there almost as securely as if it was knotted.

At the last letter there is a special rule: stretch the nozzle of the balloon (the place where you started) and wrap it around the twist where you finished. Ta da!



You started with an abstract word in a four letter alphabet (the genotype) and have twisted the observable entity it specifies (the phenotype.) Each edit in the derivation of the word can be seen as a mutation.

Can these particular mutations ever produce a word with an odd number of letters? A word that ends with an open letter?

Can more than one word specify (map to) the same phenotype?

Why do we allow only one mutation per generation? (Is it ever likely that two closely interacting mutations would originate in a single individual?)

If we splice or insert one of these genotypes into another genotype, is the result still a word we can twist?

For longer words, you will need to stop after completing the last letter the current balloon can accommodate. Then stretch and wrap the nozzle of the next balloon around the last twist, and keep going!