Was our ancestor a hyperthermophilic procaryote?

Area of Science:

• Evolutionary Biology
• Molecular Biology
• Origin of Life Studies

Background:

• The 'classical' model proposes hyperthermophilic prokaryotes as the ancestors of all life.
• This model suggests Archaea, Bacteria, and Eucarya evolved from these heat-loving ancestors.

Purpose of the Study:

• Critically review the classical model for the emergence of the three domains of life.
• Propose an alternative model for the last common ancestor and the early evolution of life.

Main Methods:

• Literature review and critical analysis of existing models.
• Comparative analysis of lipid structures and evolutionary pressures.

Main Results:

• The last common ancestor was likely a non-hyperthermophilic protoeukaryote with sn-1,2 glycerol ester lipids.
• Archaea likely evolved from this ancestor, adapting to heat via molecular innovation (sn-2,3 glycerol ether lipids).
• Early Bacteria may have evolved through convergent mechanisms, possibly involving lateral gene transfer from Archaea.

Conclusions:

• The classical model of hyperthermophilic prokaryote ancestry is challenged.
• A protoeukaryotic ancestor with specific lipid characteristics is proposed.
• The evolution of Archaea and Bacteria involved adaptation to thermal environments and potentially horizontal gene transfer.