Language Evolution and Computation Bibliography

In this paper, we introduce a framework for simulating cultural process. The general idea is to simulate a world in which learning agents create external structures which mediate their behavior. This simulation demonstrates the simple (but very important) concept that such a system is capable, through generations of time, of producing agents endowed with cognitive powers that are not attainable in the lifetime of any individual agent. We argue that such an outcome is possible without effecting the genetic organization of individuals. However, we also argue that the cultural process is capable of guiding both learning and phylogenetic evolution, which leaves open the possiblity of genetic organization tracking cultural process.

A complete understanding of communication, language, intention- ality and related mental phenomena will require a theory integrating mechanistic explanations with ethological phenomena. For the foresee- able future, the complexities of natural life in its natural environment will preclude such an understanding. An approach more conducive to carefully controlled experiments and to the discovery of deep laws of great generality is to study synthetic life forms in a synthetic world to which they have become coupled through evolution. This is the approach of synthetic ethology. Some simple synthetic ethology ex- periments are described in which we have observed the evolution of communication in a population of simple machines. We show that even in these simple worlds we find some of the richness and complexity found in natural communication.

A population of artificial organisms evolved simple communication protocols for mate finding. Female animals in our artificial environment had the ability to see males and to emit sounds. Male animals were blind, but could hear signals from females. Thus, the environment was designed to favor organisms that evolved to generate and interpret meaningful signals. Starting with random neural networks, the simulation resulted in a progression of generations that exhibit increasingly effective mate-finding strategies. In addition, a number of distinct subspecies, i.e., groups with different signaling protocols or 'dialects,' evolve and compete. These protocols become a behavioral barrier to mating that supports the formation of distinct subspecies. Experiments with physical barriers in the environment were also performed. A partially permeable barrier allows a separate subspecies to evolve and survive for indefinite periods of time, in spite of occasional migration and contact from members of other subspecies.

In an earlier paper it was shown that linguistic families of languages spoken by a set of 38 populations associate rather strongly with an evolutionary tree of the same populations derived from genetic data. While the correlation was clearly high, there was no evaluation of statistical significance; no such test was available at the time. This gap has now been filled by adapting to this aim a procedure based on the consistency index, and the level of significance is found to be much stronger than 10(-3). Possible reasons for coevolution of strictly genetic characters and the strictly cultural linguistic system are discussed briefly. Results of this global analysis are compared with those obtained in independent local analysis.

One of the properties that most conspicuously distinguishes human language from any other form of animal communication is generativity. Language with this property therefore presumably evolved with the Homo line somewhere between H. habilis and H. sapiens sapiens. Some have suggested that it emerged relatively suddenly and completely with H. sapiens sapiens, and this view is consistent with (a) linguistic estimates as to when vocal language emerged, (b) the relatively late 'explosion' of manufacture and cultural artifacts such as body ornamentation and cave drawings, and (c) evidence on changes in the vocal apparatus. However, evidence on brain size and developmental patterns of growth suggests an earlier origin and a more continuous evolution. I propose that these scenarios can be reconciled if it is supposed that generative language evolved, perhaps from H. habilis on, as a system of manual gestures, but switched to a predominantly vocal system with H. sapiens sapiens. The subsequent 'cultural explosion' can then be attributed to the freeing of the hands from primary involvement in language, so that they could be exploited, along with generativity, for manufacture, art, and other activities.