The universal ancestor

June 9, 1998
95 (12) 6854-6859

Abstract

A genetic annealing model for the universal ancestor of all extant life is presented; the name of the model derives from its resemblance to physical annealing. The scenario pictured starts when “genetic temperatures” were very high, cellular entities (progenotes) were very simple, and information processing systems were inaccurate. Initially, both mutation rate and lateral gene transfer levels were elevated. The latter was pandemic and pervasive to the extent that it, not vertical inheritance, defined the evolutionary dynamic. As increasingly complex and precise biological structures and processes evolved, both the mutation rate and the scope and level of lateral gene transfer, i.e., evolutionary temperature, dropped, and the evolutionary dynamic gradually became that characteristic of modern cells. The various subsystems of the cell “crystallized,” i.e., became refractory to lateral gene transfer, at different stages of “cooling,” with the translation apparatus probably crystallizing first. Organismal lineages, and so organisms as we know them, did not exist at these early stages. The universal phylogenetic tree, therefore, is not an organismal tree at its base but gradually becomes one as its peripheral branchings emerge. The universal ancestor is not a discrete entity. It is, rather, a diverse community of cells that survives and evolves as a biological unit. This communal ancestor has a physical history but not a genealogical one. Over time, this ancestor refined into a smaller number of increasingly complex cell types with the ancestors of the three primary groupings of organisms arising as a result.

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Acknowledgments

I am indebted to Gary Olsen, Charles Kurland, and Ross Overbeek, for critical suggestions regarding details of the argument, to Norman Pace and David Graham for important suggestions as to making the final manuscript more readable, and to Claudia Reich for editorial suggestions. I am most indebted to Gary Olsen for the amount of time, trenchant analysis, and care he put into helping me present this thesis in an understandable manner. The author is supported in part by a grant from the National Aeronautics and Space Administration.

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Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 95 | No. 12
June 9, 1998
PubMed: 9618502

Classifications

Submission history

Accepted: April 3, 1998
Published online: June 9, 1998
Published in issue: June 9, 1998

Keywords

  1. progenote
  2. lateral gene transfer
  3. genetic annealing
  4. evolutionary temperature
  5. communal ancestor

Acknowledgments

I am indebted to Gary Olsen, Charles Kurland, and Ross Overbeek, for critical suggestions regarding details of the argument, to Norman Pace and David Graham for important suggestions as to making the final manuscript more readable, and to Claudia Reich for editorial suggestions. I am most indebted to Gary Olsen for the amount of time, trenchant analysis, and care he put into helping me present this thesis in an understandable manner. The author is supported in part by a grant from the National Aeronautics and Space Administration.

Authors

Affiliations

Carl Woese*
Department of Microbiology, University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory, MC-110, 601 South Goodwin Avenue, Urbana, IL 61801

Notes

*
To whom reprint requests should be addressed. e-mail: [email protected].
Contributed by Carl R. Woese

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    The universal ancestor
    Proceedings of the National Academy of Sciences
    • Vol. 95
    • No. 12
    • pp. 6571-7230

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