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The last common bilaterian ancestor.

Douglas H Erwin1, Eric H Davidson

  • 1Department of Paleobiology, National Museum of Natural History, Washington, D.C. 20560, USA. erwin.doug@nmnh.si.edu

Development (Cambridge, England)
|June 19, 2002
PubMed
Summary

The study challenges the conventional view of the early bilaterian ancestor, suggesting a simpler body plan. This impacts how we interpret fossil evidence for animal evolution.

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Area of Science:

  • Evolutionary developmental biology
  • Comparative genomics
  • Paleontology

Background:

  • Regulatory gene similarities in Drosophila and chordate development suggest shared ancestry.
  • Conventional view posits a complex protostome-deuterostome ancestor (PDA) with modern bilaterian body parts.
  • This view implies significant ancestral complexity and early evolution of body plans.

Purpose of the Study:

  • To propose an alternative model for the body plan of the last common protostome-deuterostome ancestor (PDA).
  • To re-evaluate the interpretation of conserved regulatory genes in bilaterian evolution.
  • To adjust expectations for Neoproterozoic fossil evidence of bilaterian origins.

Main Methods:

  • Comparative analysis of regulatory gene function across diverse bilaterian phyla.
  • Phylogenetic reconstruction of ancestral bilaterian body plans.
  • Reinterpretation of existing paleontological data in light of revised ancestral models.

Main Results:

  • Evidence suggests regulatory gene conservation may not always reflect deep homology of complex structures.
  • An alternative model proposes a less complex body plan for the last common PDA.
  • This revised model offers a new framework for understanding early bilaterian evolution.

Conclusions:

  • The conventional view of a complex PDA may be an overestimation.
  • A simpler ancestral body plan reconciles gene data with fossil interpretations.
  • This research reframes the search for and interpretation of early bilaterian fossils.
Keywords:
NASA Discipline Evolutionary BiologyNASA Discipline ExobiologyNon-NASA Center

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