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Proceedings of the Royal Society B: Biological Sciences
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A generative bias towards average complexity in artificial cell lineages

Published:01 May 2007https://doi.org/10.1098/rspb.2007.0399

    Abstract

    The evolution of life on earth has been characterized by generalized long-term increases in phenotypic complexity. Although natural selection is a plausible cause for these trends, one alternative hypothesis—generative bias—has been proposed repeatedly based on theoretical considerations. Here, we introduce a computational model of a developmental system and use it to test the hypothesis that long-term increasing trends in phenotypic complexity are caused by a generative bias towards greater complexity. We use our model to generate random organisms with different levels of phenotypic complexity and analyse the distributions of mutational effects on complexity. We show that highly complex organisms are easy to generate but there are trade-offs between different measures of complexity. We also find that only the simplest possible phenotypes show a generative bias towards higher complexity, whereas phenotypes with high complexity display a generative bias towards lower complexity. These results suggest that generative biases alone are not sufficient to explain long-term evolutionary increases in phenotypic complexity. Rather, our finding of a generative bias towards average complexity argues for a critical role of selective biases in driving increases in phenotypic complexity and in maintaining high complexity once it has evolved.

    Footnotes

    †Present address: School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK.

    References

    Figure 1a and references to figure 15 in the electronic supplementary material are now correct. 26 February 2007

    Notice of correction

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