Abstract
We re-evaluate research relating to the current theories of the emergence of biological systems. The challenge being that research programmes concerning the emergence of these systems are viewed as the same as those relating to the origin of cells. Cells are strikingly important biological entities, hard wired into the entire field of biology. The development of biological systems took place much earlier than the origin of cells and even before the existence of the Last Universal Common Ancestor (LUCA); a period which could be construed as being preLUCA and which would have taken place during in a ribonucleoprotein world. This latter entity was named FUCA (First Universal Common Ancestor) and could be viewed as a “great-grandmother” to LUCA, from which the three domains of life, namely Archaea, Bacteria, and Eukarya (emerging as a chimera of the two) evolved. RNA-world theories are the focus of mainstream research programmes for the origin of life stricto sensu. In the RNA-world view, self-replication of nucleic acids is seen as one of the most relevant events in the pre-biotic world. Without denying the relevance of self-replication, we argue here that the most germane event which occurred in the pre-biotic world was the crosstalk between nucleic acids and peptides. When these two macromolecules started to interact, the singularity that aggregated the complexity required to produce life began to emerge. Thus, comprehension of the early origins of the translation machinery and the assembly of the genetic code is key. Therefore, the relevance of cell theory and self-replication should be re-evaluated as well as the concept of life itself.
Highlights
(LUCA); i.e. the latter is the first cellular life form
Without denying the relevance of self-replication, we argue here that the most germane event which occurred in the pre-biotic world was the crosstalk between nucleic acids and peptides
According to the RNA-world theory, life may not have a cellular origin as purported by the cell unit hypothesis; life could be the result of the interaction between small RNA-like molecules that were capable of performing both catalytic activity as well as being custodians of information [10,11]
Summary
During the mid-nineteenth century, biology experienced an exponential structural and conceptual revolution whereby new ways of understanding biological processes were brought into focus. Despite the steady growth of molecular biology during the 1960s and 1970s, the paradigm of the cell as a necessary unit for life remained unshaken until the early 1980s, when RNA molecules were discovered to have catalytic activity, as in ribozymes [8,9] These discoveries led to the understanding that living cellular systems have two essential properties, namely information carrying and catalysis. According to the RNA-world theory, life may not have a cellular origin as purported by the cell unit hypothesis; life could be the result of the interaction between small RNA-like molecules that were capable of performing both catalytic activity as well as being custodians of information [10,11] Under such a paradigm, DNA and proteins were nothing more than further specializations acquired by RNAs to improve the performance of the aforementioned functions [12]. We can “define” life as commencing with the emergence of FUCA, at the point at which a first self-referential circle of molecules sparked life
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