1

Technology and Technology and the Evolution of Complexity the Evolution of Complexity

Human Complex Systems, Feb 23, 2007

W. Brian Arthur External Professor, Santa Fe Institute

2

How does the collective of technology How does the collective of technology evolve over time?evolve over time?

And what does this say about the evolution of complexity?

3

Consider … Consider …

1. Novel technologies are constructed from existing technologies

2. … and offer themselves as components—building blocks for the construction of further technologies

4

Technology Builds Itself from Itself Technology Builds Itself from Itself

Technology is autopoietic or self-creating:

– New elements build from existing ones

– Complication builds from simplicity

5

W. F. Ogburn’s Claim (1922)W. F. Ogburn’s Claim (1922)

“It would seem that the larger the equipment of material culture, the greaterthe number of inventions. … The more there is to invent with, the greaterwill be the number of inventions. When the existing material culture issmall, embracing a stone technique and a knowledge of skins and somewoodwork, the number of inventions is more limited than when the cultureconsists of a knowledge of a variety of metals and chemicals and the use ofsteam, electricity, and various mechanical principles such as the screw, thewheel, the lever, the piston, belts, pulleys, etc. The street car could not havebeen invented from the material culture existing at the last glacial period.The discovery of the power of steam and the mechanical technology existingat the time made possible a large number of inventions.” -- Social Change,1922.

6

Exponential buildup of technology?Exponential buildup of technology?

• Dubious: Many combinatorics possible– (Simplest gives 2N – N – 1 possible technologies)

• Diminishing returns to novelty or to demand possible

7

An Experiment at FXPALAn Experiment at FXPALW. Brian Arthur and Wolfgang PolakW. Brian Arthur and Wolfgang Polak

Idea

- Create an artificial world in which the technologies are logic circuits

- Give this world “logic needs” to be potentially fulfilled

- Allow the system to create technologies to fulfill these

by combining previous technologies

8

Rules of the ExperimentRules of the Experiment

1. Start from one primitive (NAND gate)

2. Make circuits by random combination of existing elements

3. Check to see if any needs (target logic purposes) are fulfilled

4. If so, these novel circuits become new building blocks

5. Better versions (simpler ones) replace previous versions

9

Tech 20Tech 20

10

1-bit adder1-bit adder

11

2-bit adder2-bit adder

12

Tech 33: And-3Tech 33: And-3

13

3-bit adder3-bit adder

14

4-bit adder4-bit adder

15

We Find …  We Find …  

1. Quite complicated circuits evolve– An 8-bit adder (16 inputs, 9 outputs) is one

of 10177,554 possible circuits

16

We Find …  We Find …  

2. Complicated circuits require intermediate steps

– … and intermediate needs

– (Cf. R. Lenski et al. Evol. Origin of Complex Features)

17

We Find …  We Find …  

3. Buildup is history dependent

– New technologies build on what is

18

Figure 5: Implication, being invented before negation in this example, is used more heavily. Usagedeclines over time as better technologies are invented.

19

We Find …  We Find …  

4. Sudden appearance of key circuits (enabling technologies) then quick use of these

– Full adder appears after 32,000 steps; 2,3,4-bit adders

quickly after that

20

Gales of DestructionGales of Destruction

When a technology disappears (is replaced) a technology it used may have no further use. That tech then disappears … etc.

Q. Are these gales “sand-pile avalanches”? –I.e. is the system at self-organized criticality?

21

Avalanches of destruction follow a power lawAvalanches of destruction follow a power law

22

Summary: a different viewSummary: a different view

• Technology is a self-constructing “chemistry”(-cf. genetic regulatory networks)

• Technology bootstraps in numbers and complication

• Innovation: places of generative interaction important – Where a chemistry is generated, harbored, nurtured

23

The Process as Evolutionary AlgorithmThe Process as Evolutionary Algorithm

• Our algorithm creates a library of functionalities by constructing new objects from previously existing ones

• Differs from genetic algorithm or GP in several ways