Spent some time on Nature and PubMed. Fun 30 minutes.
The conclusion of biologists is that the hypothesis of universal common ancestry isn't even in dispute, although there is dispute over whether such a thing as a single organism Universal Common Ancestor actually existed or not. Bit of a back and forth over that, with some papers claiming its basically unknowable because of the gradualistic and artificial nature of the life/non-life distinction, and others claiming to have narrowed down some of LUCA's characteristics and found more plausible evidence supporting
Some indicative samples:
Kooinin and Wolf 2010:
A formal demonstration of the Universal Common Ancestry hypothesis has not been achieved and is unlikely to be feasible in principle. Nevertheless, the evidence in support of this hypothesis provided by comparative genomics is overwhelming.
Martins and Posada 2014:
A phylogenetic model selection test to quantify the evidence for the Universal Common Ancestry (UCA) of life forms was proposed recently (
Theobald 2010), based on the comparison of the statistical support, using likelihoods, the Akaike Information Criterion or Bayes Factors, for two different phylogenetic models representing the UCA and the Independent Origins (IO) hypotheses (
Sober and Steel 2002). In this test, the former is represented by a single phylogeny connecting all sequences, while the latter is depicted by several, independent phylogenetic trees (
Figure 1).
Importantly, in the original UCA test the same alignment was used to represent both hypotheses. When applied to a particular data set of 23 universally conserved proteins, the test strongly favored a UCA scenario.
The evidence for universal common ancestry (UCA) is vast and persuasive.
Koskela and Annila 2012:
Genomic sequences across diverse species seem to align towards a common ancestry, eventually implying that eons ago some universal antecedent organism would have lived on the face of Earth. However, when evolution is understood not only as a biological process but as a general thermodynamic process, it becomes apparent that the quest for the last universal common ancestor is unattainable. Ambiguities in alignments are unavoidable because the driving forces and paths of evolution cannot be separated from each other. Thus tracking down life’s origin is by its nature a non-computable task. The thermodynamic tenet clarifies that evolution is a path-dependent process of least-time consumption of free energy. The natural process is without a demarcation line between animate and inanimate.
Weiss et al 2016:
The concept of a last universal common ancestor of all cells (LUCA, or the progenote) is central to the study of early evolution and life's origin, yet information about how and where LUCA lived is lacking. We investigated all clusters and phylogenetic trees for 6.1 million protein coding genes from sequenced prokaryotic genomes in order to reconstruct the microbial ecology of LUCA. Among 286,514 protein clusters, we identified 355 protein families (∼0.1%) that trace to LUCA by phylogenetic criteria. Because these proteins are not universally distributed, they can shed light on LUCA's physiology. Their functions, properties and prosthetic groups depict LUCA as anaerobic, CO2-fixing, H2-dependent with a Wood-Ljungdahl pathway, N2-fixing and thermophilic. LUCA's biochemistry was replete with FeS clusters and radical reaction mechanisms. Its cofactors reveal dependence upon transition metals, flavins, S-adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium. Its genetic code required nucleoside modifications and S-adenosyl methionine-dependent methylations. The 355 phylogenies identify clostridia and methanogens, whose modern lifestyles resemble that of LUCA, as basal among their respective domains. LUCA inhabited a geochemically active environment rich in H2, CO2 and iron. The data support the theory of an autotrophic origin of life involving the Wood-Ljungdahl pathway in a hydrothermal setting.
Asserting "The claim that all complex life forms evolved from one single cell is the largest con ever perpetrated on the world, IMO" is, IMO, the height of arrogance and intellectual dishonesty.
Enjoy the reading.