"Being able to group different kinds of organisms together into larger groups is nice, but how they're connected at the very early stages of cellular evolution is still very problematic," says Gray. "The idea of how organisms and their cells evolve is still a big burning question".
What makes the endosymbiosis in trypanosomatids a special model to study cellular evolution is the fact that each protozoan contains only one symbiotic bacterium, indicating that the host imposes tight control over the endosymbiont division.
This argument will probably not be resolved on the basis of which theory of the origin of cells is more elegant since most of the ideas of early cellular evolution are highly speculative.
One issue that we have with Woese's view of early cellular evolution is that he does not clearly distinguish between two different phenomena that would occur if the HGT rate were very large: the loss of coherence of the species and the loss of coherence of the genome.
Claims that viruses are alive and predate cellular evolution can be understood only within the framework of a strict geneticist view of life based exclusively on the property of evolution and using the definition of the term "virus" as a relaxed metaphor for self-replicating entities something which viruses, strictly speaking, are not.
The Periodic charts could be considered as a reliable and refreshable platform through which the cellular evolution could be patterned and characterized.
Given that this is such a diverse protein family spanning essentially the whole history of cellular evolution, there is some uncertainty here, but one thing about their reconstructed phylogeny really leapt out at me.
Cellular differentiation and evolution are stochastic processes that can involve multiple types (or states) of particles moving on a complex, high-dimensional state-space or "fitness" landscape.
Since the mid 1970s, cancer has been described as a process of Darwinian evolution, with somatic cellular selection and evolution being the fundamental processes leading to malignancy and its many manifestations (neoangiogenesis, evasion of the immune system, metastasis, and resistance to therapies).
In both cases, consensus emerged that somatic (within-body) cellular selection and evolution is the fundamental process by which neoplasms arise, acquire malignancy, and evade therapeutic interventions (Frank and Nowak 2004; Crespi and Summers 2005; Maley and Reid 2005; Merlo et al. 2006).
