While recently discussing the precise mechanism of evolution,after viewing "What Darwin Never Knew" on Nova on PBS, there was much argument over whether the 'random' nature of mutation is truly random or conforms loosely to a framework of rules.
Evolution in organisms, as we commonly understand, is where random mutations occur, of which the traits most conducive to the survival of the species are preserved by 'natural selection'. But the term 'random mutations' doesn't imply that every possible combination will occur and have at least one or more organisms which could survive and show up in the fossil record. These mutations are governed by certain rules, some transformations being more probable than the other. One such mechanism is termed 'biased gene conversion', a far cry from the initial assumption that the word 'random' implies. For instance, certain types of amino acid pairs in DNA are favored over others, leading to certain mutations being much more probable using those pairs.
Clearly,the Theory of Evolution is itself evolving with the times and as more discoveries are made, much like we progressed from simple models of the atom to the weirdnesses of quantum mechanics and particle physics.
But what does this have to do with prions and primordial soups? What does the origin of life have to do with the origin of species?
It might be a leap of logic from one to the other, but maybe someone could talk me out of this idea.
Prions, malfunctioning proteins (less complex than DNA and RNA, considered the basic building blocks of life), have been found to evolve, despite their falling under the category of 'non-living' per the DNA/RNA definition.
"On the face of it, you have exactly the same process of mutation and adaptive change in prions as you see in viruses," said Charles Weissmann, M.D., Ph.D., the head of Scripps Florida's Department of Infectology, who led the study. "This means that this pattern of Darwinian evolution appears to be universally active. In viruses, mutation is linked to changes in nucleic acid sequence that leads to resistance. Now, this adaptability has moved one level down -- to prions and protein folding -- and it's clear that you do not need nucleic acid for the process of evolution."
A path to an answer to the major question of how life could have possibly started on a 'lifeless' planet covered with 'a primordial soup' now presents itself. Could it be a 'prion' like molecule, or an even simpler version that started to replicate itself, 'evolving' as the millenia passed?
In the study of early life on Earth, one name towers above the rest: LUCA. LUCA is not the name of a famous scientist in the field; it is shorthand for Last Universal Common Ancestor, a single cell that lived perhaps 3 or 4 billion years ago, and from which all life has since evolved. Amazingly, every living thing we see around us (and many more that we can only see with the aid of a microscope) is related. As far as we can tell, life on Earth arose only once.
Is it possible that LUCA may not been the 'true ancestor' of all cells, just as the atom was not the final frontier in the deconstruction of matter? The prion evolution discovery portends exciting possibilities into understanding the true mechanisms behind how a 'lifeless mix of chemicals' could indeed generate life as we now know it.