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The origin of animals: can molecular clocks and the fossil record be reconciled?

Published version
Peer-reviewed

Type

Article

Change log

Authors

Cunningham, JA 
Liu, AG 
Bengtson, S 
Donoghue, PCJ 

Abstract

The evolutionary emergence of animals is one of the most significant episodes in the history of life, but its timing remains poorly constrained. Molecular clocks estimate that animals originated and began diversifying over 100 million years before the first definitive metazoan fossil evidence in the Cambrian. However, closer inspection reveals that clock estimates and the fossil record are less divergent than is often claimed. Modern clock analyses do not predict the presence of the crown-representatives of most animal phyla in the Neoproterozoic. Furthermore, despite challenges provided by incomplete preservation, a paucity of phylogenetically informative characters, and uncertain expectations of the anatomy of early animals, a number of Neoproterozoic fossils can reasonably be interpreted as metazoans. A considerable discrepancy remains, but much of this can be explained by the limited preservation potential of early metazoans and the difficulties associated with their identification in the fossil record. Critical assessment of both records may permit better resolution of the tempo and mode of early animal evolution.

Description

Keywords

Cambrian explosion, ediacaran, metazoa, molecular clocks, neoproterozoic, trace fossils

Journal Title

BioEssays

Conference Name

Journal ISSN

0265-9247
1521-1878

Volume Title

39

Publisher

Wiley
Sponsorship
Natural Environment Research Council (NE/L011409/2)
JAC and AGL acknowledge support from Natural Environment Research Council (NERC) Fellowships [grant numbers NE/J018325/1 and NE/L011409/1]. SB and JAC acknowledge funding from the Danish National Research Foundation [DNRF53] and the Swedish Research Council [2013-4290]. PCJD was supported by a Royal Society Wolfson Merit Award, a Leverhulme Trust Research Fellowship and a NERC standard grant [NE/F00348X/1].