The Watchmaker's Manual

1. Before you start

What you are looking at

In the mid-1980s, while writing The Blind Watchmaker (1986), the biologist Richard Dawkins wrote a program on his Apple Macintosh. He wanted to see whether the simplest possible model of evolution, random mutation plus selection, repeated over many generations, could build something that looks designed. The result was this program. The screen in front of you is a faithful recreation of it (version 1.1, 1993), right down to the black-and-white pixels.

The little drawings are biomorphs, a word Dawkins took from the zoologist and surrealist painter Desmond Morris, who used it for the animal-like shapes in his paintings. Each biomorph is grown from a short list of numbers, its genes. You never draw a biomorph. You choose which ones get to have offspring, and the offspring inherit their parent's genes with occasional small copying errors: mutations. That is all. Everything you will see, from trees to insects to things that look like chandeliers, comes from repeating those two steps.

Four of Dawkins' own biomorphs, from his "Exhibition zoo" file.

Working a 1980s Macintosh

The original ran on a Mac with a 9-inch black-and-white screen, and the recreation behaves the same way. A few habits from 1986 are worth knowing.

• Menus. Press on a menu title (say Operation), slide down to an item and let go. Or click the title once to open it and click the item. Items in grey are not available at the moment.
• Keyboard shortcuts. Most menu items show a ⌘ letter. You can type just the letter: press B to Breed, E for Engineering, and so on. Avoid ⌘W and ⌘Q in the browser: they close the tab or quit the browser. Use the File menu to quit.
• The pointer tells you the mode. A cross means breeding; a die means Hopeful Monster; a syringe means Engineering; a hand, scissors or gun mean you are rearranging a pedigree. During animations the pointer disappears. Nudge the mouse and it comes back.
• There is no Undo. If you like a biomorph, save it before you move on (Edit ▸ Add Biomorph to Album, or just press A).

How a biomorph grows

A biomorph is not stored as a picture. It is grown, a little like an embryo, by following a simple rule over and over. Start with a trunk. At its tip, sprout two branches, one leaning left and one leaning right. At the tip of each of those, sprout two more, and so on. Gene 9 says how many times to repeat the forking, so each extra step doubles the number of twigs.

The same tree with its forking repeated 2 to 7 times (gene 9). Everything else is identical.

The other genes set the lengths and angles of the branches at each kind of fork. Because the same few numbers are reused at every fork, one small change to a gene alters the whole drawing at once. That is the important idea: genes are a recipe, not a blueprint. A blueprint would have one number per twig; a recipe describes a process, and the shape emerges from it. Real genes work the same way, through development.

The sixteen genes

The strip across the top of the screen has one box per gene. Point at any biomorph and the strip shows its genes. Dawkins' first version, the one described in the book, had only the first nine. He added the rest a few years later (see Investigation D).

A small black dot in a gene box marks a gradient: in a segmented biomorph, that gene grows (dot at the top) or shrinks (dot at the bottom) from one segment to the next, so the segments are not all alike. On gene 9 a dot means tapering: thick trunk, thin twigs. That is why the starting tree has a sturdy trunk.

One insect with the three settings of gene 13: Single, UpDn and Radial.

2. Your first ten minutes

Open the program (or reload it). It starts by breeding a litter from Dawkins' starting tree. Then try this.

1. Choose a goal. Pick something definite: the tallest, skinniest tree you can make; something with wings; something that looks like a spider. Write it down. A goal turns you into a consistent selector.
2. Look at the litter. Most of the fourteen offspring look almost exactly like their parent. Some are identical: no mutation happened to land on a gene that shows. A few differ in one small way.
3. Click the offspring closest to your goal. It glides to the centre and becomes the next parent. A line flashes out to each box (an umbilical cord, Dawkins called it) and a new litter is drawn.
4. Repeat for twenty or thirty generations. Don't wait for a perfect child: take any step in the right direction.
5. When you like the result, press A to add it to the Album, then carry on breeding. Press H at any time for the program's own help on what you are doing.

If you get stuck

Nothing seems to change.

Click the parent itself (the centre box) for a fresh litter. If change is still too slow, choose Engineering and raise gene 15, the mutation size, by clicking the right-hand third of its box; then choose Breed again.

My biomorph is cut off at the edges.

Biomorphs are never shrunk to fit; they are clipped by their box, as in 1986. Choose smaller offspring for a while, or use View ▸ Fewer Columns for wider boxes. Rows and columns always stay odd, so that there is a middle box for the parent.

It has become enormous and slow to draw.

Pick offspring with fewer twigs, or lower gene 9 in Engineering.

I changed the grid and now there is only one biomorph.

That is normal. Choose Breed (B) to start a new litter in the new grid.

I lost a good one.

There is no Undo. Save as you go: A adds the current biomorph to the Album, and File ▸ Save Biomorph keeps it on the disk. Better still, turn on the Fossil record before you start (next tip).

A menu item is grey.

It does not apply in the current mode. For example, Play Back Fossils only works from the breeding screen.

3. Feature reference

One section per menu, in menu-bar order. The first menu, under the little biomorph at the far left, holds About Blind Watchmaker. Click anywhere to close the About box.

File

• Load to Album... L opens a file of biomorphs and adds them to the Album. The disk called "Blind Watchmaker" holds five of Dawkins' original files, including his Alphabet zoo and Exhibition zoo. Click Drive to open a file from your own computer instead.
• Load as Fossils... O opens a file as a fossil record and plays it back.
• Save Biomorph..., Save Fossils... F and Save Album... S save to the disk. Files saved to the disk stay in this browser on this computer. To keep a copy elsewhere, or hand one in, click Drive in the Save dialog to download it.
• Close Album empties the Album (it offers to save first).
• Quit leaves the program.

Edit

• Copy C puts a picture of the current biomorph on the clipboard, ready to paste into a report.
• Paste V and Clear work on Album slots: Clear empties a slot, and Paste fills an empty slot with the last biomorph you copied.
• Highlight Biomorph lets you pick any biomorph on the breeding screen without breeding from it: click one and its box turns black. It becomes the "active" biomorph that Engineering, Drift, Save and so on will use.
• Add Biomorph to Album A files the current biomorph on the next free Album page. The page flashes up, then you are returned to where you were.
• Show Album shows the Album. With more than one page you first see miniatures of all the pages: click one to open it, then click a biomorph to select it.

Operation

Breed B

The heart of the program. The current biomorph becomes a parent in the centre box and its offspring fill the rest. Click an offspring to make it the next parent; click the parent for a new litter. Point at any box to read its genes in the strip.

Drift D

Mutation without selection. The biomorph changes by one random mutation after another, and nobody chooses. Drift only runs while the pointer is inside the window: move up to the menu bar to pause, and choose another operation to stop. View ▸ Drift Sweep shows the lineage spread across the boxes instead of one picture at a time.

Engineering E

Change genes directly, like a genetic engineer, instead of breeding. Move the pointer up into the gene strip ("the chromosome"). Over the left third of a box it becomes a left arrowhead: click to lower that gene. The right third raises it. Hold the button to repeat. In boxes 1–9 and 11, the middle third sets a gradient: upper part = increasing, middle = none, lower = decreasing. Elsewhere the pointer is a hypodermic syringe that does nothing (try it twice and the program will tell you so).

Hopeful Monster M

A biomorph with entirely random genes, as if made by one enormous mutation. Click anywhere for another. (The name comes from the geneticist Richard Goldschmidt, who thought new species might appear in single large jumps.)

Fossils: Initialize Fossil Record I, Play Back Fossils, Recording Fossils R

Recording starts switched off. Initialize Fossil Record empties the record and starts recording: from then on, every parent you choose while breeding is saved, oldest first. Recording Fossils switches recording off and on. Play Back Fossils (from the breeding screen) opens a window with a scroll bar. The newest fossil is at the top; drag the scroll box down, or click the arrows, to sink back through the strata. Drag the window by its title bar and resize it from the bottom-right corner. In the Exit menu, Breed from Current Fossil starts breeding again from the ancestor on show, and Close Window returns you to the breeding screen.

Triangle T

Explore "Biomorph Land", the space of all possible biomorphs. Three anchor biomorphs sit at the corners of a triangle. Every point inside is a blend of their genes, weighted by how close it is to each corner. As you move the mouse, the pointer itself becomes a tiny picture of the biomorph you would get there. Click to draw it full size. Points outside the triangle extrapolate beyond the anchors.

View

• More / Fewer Rows and More / Fewer Columns change the breeding grid (always odd numbers; up to 99 boxes). Choose Breed afterwards to fill it.
• Thicker Pen and Thinner Pen (Engineering only) change the line width, for bolder pictures.
• Drift Sweep switches Drift between one picture at a time and a sweep across the boxes.
• Make top / left / right of triangle replaces a Triangle anchor with the current biomorph.

Mutations

Each item switches one kind of mutation on (ticked) or off. A switched-off kind is frozen: those genes are inherited unchanged. Genes 1 to 9 can always mutate.

Pedigree

A family tree you grow by hand. Display pedigree 1 puts the current biomorph in the middle of the screen in a box with a double border. A double border marks an Adam: a biomorph with no parent. Then:

• Draw Out Offspring 2: press inside a box and drag outwards. A line follows the pointer; let go and a mutant child is born where it ends, joined to its parent by a line. With Single Mirror 4 or Double Mirrors 5 you draw out two or four children at once (No Mirrors 3 returns to one).
• Move 6: drag boxes around. They stack like little windows, and the lines follow.
• Detach 7: snip a biomorph (and its descendants) away from its parent. It becomes a new Adam.
• Kill 8: remove a biomorph and all its descendants. There is no Undo.

Help

Help with current operation H shows the program's own short help for the mode you are in. Miscellaneous Help covers the grid and the Mutations menu.

Keyboard summary

4. Investigations

Each investigation stands on its own and takes 10 to 25 minutes. They are ways of asking the program questions about evolution. Work in pairs if you can: one at the mouse, one keeping notes, then swap. Each one ends with questions to think about. There are no trick questions, but the best answers connect what you saw on the screen to what happens in real populations.

5. Questions, glossary and further reading

Big questions to discuss

1. The biomorphs look designed, but nobody designed them. What, exactly, did the designing?
2. Why does evolution by cumulative selection need small steps? Could it work with large ones?
3. Most mutations made little visible difference, and a few made a big one. Is that realistic?
4. The program shows that cumulative selection is powerful. What does it not show about evolution in nature?
5. If you ran your breeding session again from the same tree with the same goal, would you end up with the same biomorph? What does that suggest about replaying the history of life?

Glossary

Adam

In a pedigree, a biomorph with no parent (shown with a double border).

Artificial selection

Breeding in which a person chooses which individuals reproduce, as with crops, pigeons and dogs.

Biomorph

One of the program's computer creatures, grown from a short list of genes.

Biomorph Land

Dawkins' name for the space of all possible biomorphs, in which every biomorph sits next to those it differs from by one mutation.

Cumulative selection

Selection repeated over many generations, each one starting from the results of the last, so that small improvements add up.

Development (embryology)

The process by which genes build a body. In the program, the recursive branching rule.

Drift (in this program)

A lineage changing by random mutation with no selection. Not quite the same as genetic drift in a population.

Epistasis

When the effect of one gene depends on the state of others.

Evolvability

The capacity of a lineage to produce useful variation. Developmental innovations such as segmentation can increase it.

Genotype and phenotype

The genes (the numbers in the strip) and the body they build (the drawing).

Gradient

A gene whose value changes from one segment to the next.

Hopeful monster

A form produced by a single large mutation. The phrase is Richard Goldschmidt's.

Mutation

A random change in a gene when it is copied into an offspring.

Pleiotropy

When one gene affects several traits.

Segmentation

A body built from repeated units. Gene 10 in the program.

Single-step selection

Hoping that random variation produces a finished result in one go.

Further reading

• Dawkins, R. (1986). The Blind Watchmaker. Longman / Norton. Chapter 3, "Accumulating small change", introduces the biomorphs and the weasel.
• Dawkins, R. (1989). The evolution of evolvability. In C. G. Langton (ed.), Artificial Life. Addison-Wesley. Where segmentation and the other new genes were introduced.
• Dawkins, R. (1996). Climbing Mount Improbable. Viking / Norton. More computer creatures, and the idea of climbing the gentle slopes of an evolutionary landscape.
• Darwin, C. (1859). On the Origin of Species. Chapter 1, "Variation under domestication", the artificial-selection argument behind the whole program.