title: The emergence of predators in early life: there was no Garden of Eden.
abstract: BACKGROUND
  Eukaryote cells are suggested to arise somewhere between 0.85~2.7 billion years ago. However, in the present world of unicellular organisms, cells that derive their food and metabolic energy from larger cells engulfing smaller cells (phagocytosis) are almost exclusively eukaryotic. Combining these propositions, that eukaryotes were the first phagocytotic predators and that they arose only 0.85~2.7 billion years ago, leads to an unexpected prediction of a long period (approximately 1-3 billion years) with no phagocytotes -- a veritable Garden of Eden.
  
  
  METHODS
  We test whether such a long period is reasonable by simulating a population of very simple unicellular organisms -- given only basic physical, biological and ecological principles. Under a wide range of initial conditions, cellular specialization occurs early in evolution; we find a range of cell types from small specialized primary producers to larger opportunistic or specialized predators.
  
  
  CONCLUSIONS
  Both strategies, specialized smaller cells and phagocytotic larger cells are apparently fundamental biological strategies that are expected to arise early in cellular evolution. Such early predators could have been 'prokaryotes', but if the earliest cells on the eukaryote lineage were predators then this explains most of their characteristic features.
authors.affiliation: Allan Wilson Center for Molecular Ecology and Evolution, Massey University, Palmerston North, New Zealand.
authors.forename: Silvester
authors.initials: S
authors.lastname: de Nooijer
authors.forename: Barbara R
authors.initials: BR
authors.lastname: Holland
authors.forename: David
authors.initials: D
authors.lastname: Penny
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004463:Ecology; D017753:Ecosystem; D020387:Food Chain; D008954:Models, Biological; D000069497:Origin of Life; D013997:Time Factors