Meiosis and sex: potent weapons in the competition between early eukaryotes and prokaryotes.

The earliest eukaryote species almost certainly evolved in an environment dominated by numerous prokaryotic species. If the first eukaryotic cells were larger and grew more slowly than their prokaryotic neighbours, they might well have been at a competitive disadvantage. It is proposed here that the early evolution of meiosis, with its capacity for generating new favourable gene combinations, might have served to offset any such competitive disadvantages. Meiosis and sex could have arisen in an asexually reproducing species and formed a clonal population.