Technology and the Evolution of Complexity Human Complex Systems, Feb 23, 2007 W. Brian Arthur External Professor, Santa Fe Institute

How does the collective of technology evolve over time? And what does this say about the evolution of complexity?

Consider … Novel technologies are constructed from existing technologies … and offer themselves as components—building blocks for the construction of further technologies

Technology Builds Itself from Itself Technology is autopoietic or self-creating: New elements build from existing ones Complication builds from simplicity

W. F. Ogburn’s Claim (1922)

Exponential buildup of technology? Dubious: Many combinatorics possible (Simplest gives 2N – N – 1 possible technologies) Diminishing returns to novelty or to demand possible

An Experiment at FXPAL W. 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

Rules 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

Tech 20

1-bit adder

2-bit adder

Tech 33: And-3

3-bit adder

4-bit adder

We Find … Quite complicated circuits evolve An 8-bit adder (16 inputs, 9 outputs) is one of 10177,554 possible circuits

We Find … 2. Complicated circuits require intermediate steps … and intermediate needs (Cf. R. Lenski et al. Evol. Origin of Complex Features)

We Find … 3. Buildup is history dependent New technologies build on what is

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

Gales 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?

Avalanches of destruction follow a power law

Summary: 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

The 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