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IADIS International Conference WWW/Internet 2010Figure 2. Rapid growth of Wikipedia and its structureAn analysis of the March 2010 English language complete Wikipedia data dump reveals that the numberof new Wikipedia articles created and the number of new infoboxes have increased rapidly. After firstappearing in 2002, the infobox addition rate stabilized at approximately 1/10 of the article creation rate in2006, and has since closely followed the pattern of article creation.3. CULTURAL EVOLUTION LEADS TO STRUCTURENatural languages have many structural features that aid communication. For example, compositionalityallows listeners to understand a completely new word if they understand the parts from which it is composed,while syntax means that users can reliable interpret completely novel sentences by relying on the relationshipbetween the words and the way they are strung together.A dominant linguistic paradigm postulates a sophisticated, genetically inherited cognitive tool that turnssparse linguistic exposure into language competence (Chomsky, 1965 and 1995; Briscoe, 1997). As aconsequence of this assumption, many researchers link the biological evolution of cognitive abilities to agradual increase in linguistic structure (Pinker, 1992; Gould, 1979), such that less cognitively capableancestors would have spoken less structured languages. However, a new linguistic structure gene does notbenefit the individual, as he has no one who can understand the more structured language he speaks. Instead,as with infoboxes, the benefits come only from a shared structure.Regardless, the time elapsed since Wikipedia's introduction in 2001 precludes concurrent biologicalevolution as an explanation for the evolution of its structure. Cultural evolution, which substitutes learningand imitation in place of genetic inheritance, moves much faster and could be responsible. One view ofcultural evolution simply replaces genes with memes and relies on the relative net benefit of these "units ofculture" to dominate the population of cultural items, Wikipedia articles in this case, just as the genes for asuperior language ability might have come to dominate early human populations. However, this explanationrequires a recognized net benefit for relatively more structured articles, while the largely unrecognizedbenefits of structure apply across articles rather than to single articles.Fortunately, the Iterated Learning Model (ILM) is a cultural evolution framework that provides a memefreeexplanation for the evolution of language structures such as recursive syntax (Kirby, 2002),compositionality (Smith, 2003), word order universals (Kirby, 1999) and the regularity-irregularitydistinction (Kirby, 2001). In a typical ILM (Figure 3), learners are exposed to linguistic data as input, usuallyin the form of pairs of meanings and signals. From this input they attempt to form a hypothesis of thelanguage which they use to reproduce the language as output. The linguistic output is then provided as theinput to a new learner, and the cycle is repeated.If the input is unstructured then there are no patterns or relationships between meanings and signals, suchthat similar meanings have similar signals, and no way to interpret the meaning of a novel signal or predictthe signal for a novel meaning. As such, the learners would need 100% exposure to the unstructured training341