Universal common ancestry, LUCA, and the Tree of Life: three distinct hypotheses about the evolution of life

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Abstract

Common ancestry is a central feature of the theory of evolution, yet it is not clear what “common ancestry” actually means; nor is it clear how it is related to other terms such as “the Tree of Life” and “the last universal common ancestor”. I argue these terms describe three distinct hypotheses ordered in a logical way: that there is a Tree of Life is a claim about the pattern of evolutionary history, that there is a last universal common ancestor is an ontological claim about the existence of an entity of a specific kind, and that there is universal common ancestry is a claim about a causal pattern in the history of life. With these generalizations in mind, I argue that the existence of a Tree of Life entails a last universal common ancestor, which would entail universal common ancestry, but neither of the converse entailments hold. This allows us to make sense of the debates surrounding the Tree, as well as our lack of knowledge about the last universal common ancestor, while still maintaining the uncontroversial truth of universal common ancestry.

Original languageEnglish
Article number31
JournalBiology and Philosophy
Volume33
Issue number5-6
DOIs
StatePublished - Dec 1 2018

Keywords

  • Common ancestry
  • LUCA
  • Last universal common ancestor
  • Tree of Life

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