The Origin of Eukaryotes as the Most Significant Aromorphic Event: Advantages of the Eukaryotic Cell

The eukaryotic cell appeared 2.7 Ga or earlier as a result of coevolution of prokaryotic components of Archean microbial communities. The crisis events at the Archean–Proterozoic boundary, which partially destroyed the Archean prokaryotic biota, may have played an important role in the development of the first eukaryotes. The separation of the nucleus from the cytosol and the presence of heterogeneous genomes within the same cell provided the prerequisites for more efficient regulatory mechanisms of gene expression and genetic recombination, which, in turn, could have become the basis for modification variability, composite life cycles, sexual process, and, eventually, multicellular organization. The more efficient mechanisms for regulation and modification, which increased their ecological tolerance, probably gave eukaryotes an advantage during crises. The new mechanisms supporting and controlling genetic variation associated with the sexual process (copulation of gametes, meiosis) gave rise to new types of biological systems—endogamous populations and species, which stimulated intense biodiversification. The emergence of eukaryotes (as well as other higher taxa) should be regarded as being the result of coevolution of ecosystems, the biosphere, and even the Earth as a whole.