Sunday, November 1, 2009

The Tree of Life's Tap Root: Our Last Common Ancestor

Recent research suggests that the last universal common ancestor (LUCA) of all life on the planet may have arisen from a phase interface between alkaline hydrogen-emitting undersea vents and the archaic acidified iron-rich ocean (Martin and Russel 2003), giving rise to an active iron-sulphur reaction phase still present in living cells and associated with electron transport and some of the most ancient proteins, such as ferredoxin, in which differential dynamics in membranous micropores in the vents managed to concentrate polypeptides and polynucleotides to biologically sustainable levels (Baaske et. al. 2007, Budin et. al. 2009), giving rise to the RNA era, while at the same time providing a free energy source based on proton transport across membranous microcellular interfaces resulting from fatty acids also being concentrated above their critical aggregate concentration .

Fig 1a: Proposed scheme for the universal common ancestor (Martin and Russel 2003)

The universal common ancestor of the three domains of life may have thus been a proton-pumping membranous interface from which archaea and bacteria emerged as free-living adaptions. This is suggested by fundemantal differences in their cell walls and other details of evolutionary relationships among some of the oldest genes.

    • Biocosmology An overview of how the origin of life may arise from cosmic symmetry-breaking.
    • Chemist Shows How RNA Can Be the Starting Point for Life May 14, 2009 A pivotal article showing how nucleotides can be synthesized from simple molecules.
    • First Cells, Proton-Pumping and Undersea Rock Pores (Lane 2009 with abstracts pdf password "model") Oct 19, 2009 A breakthrough in understanding how the first living cells could have been created at an undersea rock-pore interface.
    • The Tree of Life: Tangled Roots and Sexy Shoots: Tracing the genetic pathway from the first eucaryotes to Homo sapiens Chris King Jan 2009
      This article is a fully referenced research review to overview progress in unraveling the details of the Tree of Life, from life's first occurrence in the hypothetical RNA-era, to humanity's own emergence and diversification, through migration and intermarriage, using research diagrams and brief discussion of the current state of the art, as of the beginning of 2009.

It has also been proposed, on the basis of the highly-conserved commonality of transcription and translation proteins to all life, but the apparently independent emergence of distinct DNA replication enzymes in archaea/eucaryotes and eubacteria, that the last universal common ancestor had a mixed RNA-DNA metabolism based on reverse transcriptase, pinpointing it to the latter phases of the RNA era (Leipe et. al. 1999).

Fig 1b: Hypothetical branching and evolution of RNA and DNA replication machinery (Leipe et. al. 1999).