On the transfer of fitness from the cell to the multicellular organism

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85 Scopus citations


The fitness of any evolutionary unit can be understood in terms of its two basic components: Fecundity (reproduction) and viability (survival). Trade-offs between these fitness components drive the evolution of life-history traits in extant multicellular organisms. We argue that these trade-offs gain special significance during the transition from unicellular to multicellular life. In particular, the evolution of germ-soma specialization and the emergence of individuality at the cell group (or organism) level are also consequences of trade-offs between the two basic fitness components, or so we argue using a multilevel selection approach. During the origin of multicellularity, we study how the group trade-offs between viability and fecundity are initially determined by the cell level trade-offs, but as the transition proceeds, the fitness trade-offs at the group level depart from those at the cell level. We predict that these trade-offs begin with concave curvature in single-celled organisms but become increasingly convex as group size increases in multicellular organisms. We argue that the increasingly convex curvature of the trade-off function is driven by the cost of reproduction which increases as group size increases. We consider aspects of the biology of the volvocine green algae - which contain both unicellular and multicellular members - to illustrate the principles and conclusions discussed.

Original languageEnglish (US)
Pages (from-to)967-987
Number of pages21
JournalBiology and Philosophy
Issue number5
StatePublished - Nov 2005


  • Body size
  • Cost of reproduction
  • Evolutionary transitions
  • Fitness
  • Germ-soma specialization
  • Individuality
  • Life-history evolution
  • Multi-level selection
  • Multicellularity
  • Volvox

ASJC Scopus subject areas

  • Philosophy
  • Agricultural and Biological Sciences(all)
  • History and Philosophy of Science


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