Reduced complexity

Measuring complexity in living organisms finds that they are less complex than expected in developmental patterns:

Nature 433, 152 - 156 (13 January 2005)

The simplicity of metazoan cell lineages
RICARDO B. R. AZEVEDO1, ROLF LOHAUS1,2, VOLKER BRAUN2, MARKUS GUMBEL2, MURALIKRISHNA UMAMAHESHWAR1, PAUL-MICHAEL AGAPOW3, WOUTER HOUTHOOFD4, UTE PLATZER2, GAËTAN BORGONIE4, HANS-PETER MEINZER2 & ARMAND M. LEROI3
1 Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001, USA
2 Division of Medical and Biological Informatics, German Cancer Research Center, D-69120, Heidelberg, Germany
3 Department of Biology, Imperial College, Silwood Park, Ascot SL5 7PY, UK
4 Department of Biology, Ghent University, B-9000 Ghent, Belgium
Correspondence and requests for materials should be addressed to R.B.R.A. (razevedo@uh.edu).

Developmental processes are thought to be highly complex, but there have been few attempts to measure and compare such complexity across different groups of organisms. Here we introduce a measure of biological complexity based on the similarity between developmental and computer programs. We define the algorithmic complexity of a cell lineage as the length of the shortest description of the lineage based on its constituent sublineages. We then use this measure to estimate the complexity of the embryonic lineages of four metazoan species from two different phyla. We find that these cell lineages are significantly simpler than would be expected by chance. Furthermore, evolutionary simulations show that the complexity of the embryonic lineages surveyed is near that of the simplest lineages evolvable, assuming strong developmental constraints on the spatial positions of cells and stabilizing selection on cell number. We propose that selection for decreased complexity has played a
  major
role in moulding metazoan cell lineages.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL 35487-0345 USA
    bivalve@mail.davidson.alumlink.com

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Received on Thu Jan 13 18:08:28 2005