English: Kandler's pre-cell theory (Kandler 1998, Figure 2.3, p.22) - Scheme of cellularisation (modified after Kandler 1994, p.155)ː Scenario of the early evolution and diversification of life through the development of a multiphenotypical population of pre-cells from which the founder groups (A, B, C) and then, from them, the precursor cells (proto-cells) of the three domains of life (Woese et al. 1990) emerged. Accordingly, a "first cell" has never existed. Instead, the development of cells (cellularisation) was a successive process of evolutionary improvement.

Important evolutionary improvements are indicated by numbers: (1) Reductive formation of organic compounds from CO or CO₂ by Me-sulfur coordinative chemistry; (2) tapping of various redox energy sources and formation of primitive enzymes and templates; (3) elements of a transcription and translation apparatus and loose associations; (4) formation of pre-cells; (5) stabilised circular or linear genomes; (6) cytoplasmic membranes; (7) rigid murein cell walls; (8) various non-murein rigid cell walls; (9) glycoproteinaceous cell envelope or glycokalyx; (10) cytoskeleton; (11) complex chromosomes and nuclear membrane; (12) cell organelles via endosymbiosis (Kandler 1998, p.22, Fig. 2.3).

References: Kandler, Otto (1994). The early diversification of life. In: Early Life on Earth. Nobel Symposium 84 (S. Bengtson, ed.) Columbia U.P., New York, pp. 152-160.

Kandler, Otto (1995). Cell Wall Biochemistry in Archaea and its Phylogenetic Implications. Journal of Biological Physics. 20 (1–4), 165–169.

Kandler, Otto (1998). The early diversification of life and the origin of the three domains: A proposal. In: Thermophiles: The keys to molecular evolution and the origin of life? (J.Wiegel, M.W.W. Adams, eds.) Taylor and Francis Ltd., London, pp. 19–31.

Woese, C.R., Kandler, O., Wheelis, M. (1990) Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. Proc. Natl. Acad. Sci. USA. 87, 4576–4579.