For more information contact Luis Rocha at rocha@lanl.gov
Last Modified: November 1, 2002
This is the abstract of a talk prepared for the International interdisciplinary seminar on new robotics, evolution and embodied cognition (IISREEC).12th to 15th November 2002, Lisbon, Portugal
Abstract: Scientific theories typically make sense of phenomena at a given level of explanation. Occasionally, phenomena that seem to belong to one level unexpectedly influence an entirely different one. These interactions are strange loops. In evolution and learning, one such strange loop, the Baldwin effect, was proposed over a century ago, and has been studied computationally for the past 15 years. In this study, we use computational techniques to explore a second strange loop, which we call genetic redistribution.
Deacon has recently proposed that complexes of genes can be integrated into functional groups as a result of environmental changes that mask and unmask selection pressures. For example, many animals endogenously synthesize ascorbic acid (vitamin C), but anthropoid primates have only a non-functional version of the crucial gene for this pathway. It is hypothesized that the loss of functionality occurred in the evolutionary past when a diet rich in vitamin C masked the effect of the gene, and its loss effectively trapped the animals in a fruit-eating lifestyle. As a result, the complex of abilities that support this lifestyle were evolutionarily bound together, forming a multilocus complex.
In this study we use evolutionary computation simulations to explore the thesis that masking and unmasking can transfer dependence from one set of genes to many sets, and thereby integrate the whole complex of genes. We use the vitamin C example, but emphasize that in this study we investigate the computational consistency of the thesis, rather than its biological credentials. We used a framework based on Hinton and Nowlan’s 1987 simulation of the Baldwin effect. Additional gene complexes and an environmental parameter were added to their basic model, and the fitness function extended. The simulation clearly demonstrates the computational consistency of the genetic redistribution effect, showing an initial advantage of endogenously synthesized vitamin C, followed by transfer of the benefit to the complex of genes that together allow the acquisition of vitamin C from the environment.
As is well-known in the modelling community, the Baldwin effect only occurs in simulations when the population of agents is “poised on the brink” of discovering the genetically specified solution. Similarly, the redistribution effect occurs in simulation under specific initial conditions: too little vitamin C in the environment, and its synthesis it is never fully masked; too much vitamin C, and the abilities required to acquire it are not tightly integrated. Both the Baldwin and the redistribution effects can be considered strange loops in the interactions between genotype and phenotype in evolution.
The Baldwin effect has been hypothesized as a potential mechanism for developing language-specific adaptations like innate Universal Grammar and other highly modular capacities. Our simulations support Deacon’s argument that the process is likely the inverse, and that the extensive neural and other anatomical consequences would not be in the form of specific innate adaptations. Instead, the power of symbolic communication as a masking agent should unmask selection on an extensive and highly distributed constellation of capacities that would collectively come under selection for their fractional contributions to the acquisition and use of language.