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Fossils, molecules and embryos: new perspectives on the Cambrian explosion
J W Valentine1, D Jablonski, D H Erwin
1Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA 94720, USA. jwv@ucmp1.berkeley.edu
Development (Cambridge, England)
|February 3, 1999
Summary
The Cambrian explosion saw the rapid evolution of animal body plans. Genomic analysis suggests key developmental systems were in place before this event, with further evolution during the Cambrian.
Area of Science:
- Paleontology
- Evolutionary Biology
- Developmental Biology
Background:
- The Cambrian explosion, 530-520 million years ago, marks the rapid appearance of diverse metazoan body plans.
- Trace fossils suggest bilaterian activity by 600 million years ago, with increased complexity leading up to the Cambrian.
- All modern animal phyla may have originated by the end of the Cambrian explosion.
Purpose of the Study:
- To investigate the timing of metazoan body plan evolution relative to molecular divergences and developmental gene presence.
- To understand the role of genomic changes during the Cambrian explosion.
Main Methods:
- Analysis of fossil evidence (trace and body fossils) from the Neoproterozoic and Cambrian periods.
- Examination of molecular divergence data and the distribution of developmental control genes (Hox genes) in metazoans.
Main Results:
- Molecular divergences predate the appearance of new body plans by tens of millions of years.
- Evidence indicates a pre-Cambrian developmental patterning system, including Hox genes.
- Significant genomic repatterning likely occurred during the Early Cambrian, facilitating novel body plan evolution.
Conclusions:
- The evolution of metazoan body plans involved a complex interplay between early molecular divergences and later genomic innovations.
- While a foundational developmental system existed before the Cambrian, the explosion itself was a period of significant genetic and developmental reorganization.
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