Which type of cell came first in evolution - the eukaryotic cell or the prokaryotic cell?
This is an interesting problem of biological evolution. The most accepted hypothesis asserts that the simpler cell, the prokaryotic cell, appeared earlier in evolution than the more difficult eukaryotic cell. The endosymbiotic hypothesis, for instance, affirms that aerobic eukaryotic cells appeared from the mutualist ecological interaction among aerobic prokaryotes and primitive anaerobic eukaryotes.