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Proc Natl Acad Sci U S A. 2009 Jan 6;106(1):24-7. doi: 10.1073/pnas.0806314106. Epub 2008 Dec 23.

Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity.

Author information

1
Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305, USA. jlpayne@stanford.edu

Abstract

The maximum size of organisms has increased enormously since the initial appearance of life >3.5 billion years ago (Gya), but the pattern and timing of this size increase is poorly known. Consequently, controls underlying the size spectrum of the global biota have been difficult to evaluate. Our period-level compilation of the largest known fossil organisms demonstrates that maximum size increased by 16 orders of magnitude since life first appeared in the fossil record. The great majority of the increase is accounted for by 2 discrete steps of approximately equal magnitude: the first in the middle of the Paleoproterozoic Era (approximately 1.9 Gya) and the second during the late Neoproterozoic and early Paleozoic eras (0.6-0.45 Gya). Each size step required a major innovation in organismal complexity--first the eukaryotic cell and later eukaryotic multicellularity. These size steps coincide with, or slightly postdate, increases in the concentration of atmospheric oxygen, suggesting latent evolutionary potential was realized soon after environmental limitations were removed.

PMID:
19106296
PMCID:
PMC2607246
DOI:
10.1073/pnas.0806314106
[Indexed for MEDLINE]
Free PMC Article

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