Testing the Cambrian explosion hypothesis by using a molecular dating technique

Testing the Cambrian explosion hypothesis by using a molecular dating technique

^*Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom; ^‡Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom; ^§Department of Bioanthropology, University of Oxford, OX2 6QS, United Kingdom; and ^¶Theoretical Biology, Massey University, Palmerston North, New Zealand

Edited by James W. Valentine, University of California, Berkeley, CA, and approved August 9, 1998 (received for review June 3, 1998)

Abstract

Molecular studies have the potential to shed light on the origin of the animal phyla by providing independent estimates of the divergence times, but have been criticized for failing to account adequately for variation in rate of evolution. A method of dating divergence times from molecular data addresses the criticisms of earlier studies and provides more realistic, but wider, confidence intervals. The data are not compatible with the Cambrian explosion hypothesis as an explanation for the origin of metazoan phyla, and provide additional support for an extended period of Precambrian metazoan diversification.

Footnotes

↵ † To whom reprint requests should be sent at the present address: Department of Zoology, University of Queensland, St. Lucia 4072, Australia. e-mail: LBromham{at}zoology.uq.edu.au.
This paper was submitted directly (Track II) to the Proceedings Office.
↵ ‖ The fossil dates used to form pairs of sequences were (in millions of years before present): Diptera-Hymenoptera, 240; Diptera/Hymenoptera-Orthoptera, 300; Collembola-Pterygota, 390; Diplostraca-Anostraca, 390; Aranaea-Scorpionida, 405; Arachnida-Merostomata, 520; Cephalochordate-Chordate, 530; Dipnoi-Tetrapoda, 412; Coelocanth-Dipnoi/Tetrapoda, 418; Osteichthyes-Dipnoi/Tetrapoda, 428; Agnatha-Gnathostoma, 510; Asteroidea-Echinoidea, 500.
ABBREVIATION:

Ma,

million years ago