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Interpreting the universal phylogenetic treeThe universal phylogenetic tree not only spans all extant life, but its root and earliest branchings represent stages in the evolutionary process before modern cell types had come into being. The evolution of the cell is an interplay between vertically derived and horizontally acquired variation. Primitive cellular entities were necessarily simpler and more modular in design than are modern cells. Consequently, horizontal gene transfer early on was pervasive, dominating the evolutionary dynamic. The root of the universal phylogenetic tree represents the first stage in cellular evolution when the evolving cell became sufficiently integrated and stable to the erosive effects of horizontal gene transfer that true organismal lineages could exist.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Woese, C. R. (University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory MC-110, 601 South Goodwin Avenue, Urbana, IL 61801-3709, United States)
Date Acquired
August 22, 2013
Publication Date
July 18, 2000
Publication Information
Publication: Proceedings of the National Academy of Sciences of the United States of America
Volume: 97
Issue: 15
ISSN: 0027-8424
Subject Category
Distribution Limits
Non-NASA Center
NASA Discipline Exobiology