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GENETIC BACKGROUND. "The founding strain is strictly asexual, and thus populations have evolved by natural selection and genetic drift acting on variation generated solely by spontaneous mutations that occurred during the experiment." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

THE BIGGEST GAP. "The gap between eukaryotes and prokaryotes is recognized as the most profound evolutionary discontinuity in the living world. This gap is reflected in the fossil record." https://lnkd.in/d-J5JBr View in LinkedIn

LONG LINEAGE. "Environmental conditions have been controlled, constant, and identical for all 12 lines. To date, each population has evolved for >44,000 generations, and samples have been frozen every 500 generations, providing a rich “fossil record”." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

LARGE DOWNSTREAM IMPACTS. "Although each change on an evolutionary path has some causal relation to the circumstances in which it arose, outcomes must eventually depend on the details of long chains of antecedent states, small changes in which may have enormous long-term repercussions." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

TEST POPULATION. "Twelve initially identical populations of Escherichia coli were founded in 1988 to investigate this issue. They have since evolved in a glucose-limited medium that also contains citrate, which E. coli cannot use as a carbon source under oxic conditions. No population evolved the capacity to exploit citrate for >30,000 generations, although each population tested billions of mutations." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

ACCIDENTS OF HISTORY. "For example, multiple beneficial mutations will arise in some unpredictable order, and those that are substituted first may differ from others in their pleiotropic effects and epistatic interactions, thus constraining some evolutionary paths while potentiating other outcomes. These accidents of history may even determine the survival or extinction of entire lineages, given the capricious and sudden nature of some environmental changes." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

DEFINING. "E. coli cells cannot grow on citrate under oxic conditions, and that inability has long been viewed as a defining characteristic of this important, diverse, and widespread species." This is to be exploited in an experiment of unicellular evolution. http://www.pnas.org/content/105/23/7899.full View in LinkedIn

RANDOM VS DETERMINISTIC EVOLUTION. "At its core, evolution involves a profound tension between random and deterministic processes. Natural selection works systematically to adapt populations to their prevailing environments. However, selection requires heritable variation generated by random mutation, and even beneficial mutations may be lost by random drift. Moreover, random and deterministic processes become intertwined over time such that future alternatives may be contingent on the prior history of an evolving population." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

HISTORICAL CONTINGENCY. "More generally, we suggest that historical contingency is especially important when it facilitates the evolution of key innovations that are not easily evolved by gradual, cumulative selection." http://www.pnas.org/content/105/23/7899.full View in LinkedIn

INDEPENDENT CONFIRMATION. "Other findings suggest that E. coli has the potential to evolve a Cit+ phenotype. Hall reported the only documented case of a spontaneous Cit+ mutant in E. coli." http://www.pnas.org/content/105/23/7899.full View in LinkedIn