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Did surface temperatures constrain microbial evolution?The proposition that glaciation may not have occurred before the Cenozoic--albeit not yet a consensus position--nevertheless raises for reconsideration the surface temperature history of the earth. Glacial episodes, from the Huronian (2.3 billion years ago; BYA) through the late Paleozoic (320 to 250 million years ago; MYA) have been critical constraints on estimation of the upper bounds of temperature (Crowley 1983, Kasting and Toon 1989). Once removed, few if any constraints on the upper temperature limit other than life remain. Walker (1982) recognized that life provides an upper limit to temperature in the Precambrian. We propose a more radical concept: the upper temperature limit for viable growth of a given microbial group corresponds to the actual surface temperature at the time of the group's first appearance. In particular, we propose here that two major evolutionary developments--the emergence of cyanobacteria and aerobic eukaryotes--can be used to determine surface temperature in the Precambrian, and that only subsequent cooling mediated by higher plants and then angiosperms permitted what may possibly be the earth's first glaciation in the late Cenozoic.
Document ID
20040089513
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Schwartzman, D.
(Howard University Washington, DC 20059, United States)
McMenamin, M.
Volk, T.
Date Acquired
August 21, 2013
Publication Date
June 1, 1993
Publication Information
Publication: Bioscience
Volume: 43
Issue: 6
ISSN: 0006-3568
Subject Category
Exobiology
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Exobiology
NASA Discipline Number 52-30
NASA Discipline Exobiology
Non-NASA Center

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