Complex cellular machines and processes are commonly believed to be products of selection, and it is typically understood to be the job of evolutionary biologists to show how selective advantage can account for each step in their origin and subsequent growth in complexity. Here, we describe how complex machines might instead evolve in the absence of positive selection through a process of "presuppression," first termed constructive neutral evolution (CNE) more than a decade ago. If an autonomously functioning cellular component acquires mutations that make it dependent for function on another, pre-existing component or process, and if there are multiple ways in which such dependence may arise, then dependence inevitably will arise and reversal to independence is unlikely. Thus, CNE is a unidirectional evolutionary ratchet leading to complexity, if complexity is equated with the number of components or steps necessary to carry out a cellular process. CNE can explain "functions" that seem to make little sense in terms of cellular economy, like RNA editing or splicing, but it may also contribute to the complexity of machines with clear benefit to the cell, like the ribosome, and to organismal complexity overall. We suggest that CNE-based evolutionary scenarios are in these and other cases less forced than the selectionist or adaptationist narratives that are generally told.

Biology Centre Institute of Parasitology Czech Academy of Sciences and Faculty of Sciences University of South Bohemia České Budĕjovice Czech Republic

Citace poskytuje Crossref.org

Lessons from the deep: mechanisms behind diversification of eukaryotic protein complexes

Complete minicircle genome of Leptomonas pyrrhocoris reveals sources of its non-canonical mitochondrial RNA editing events

A Uniquely Complex Mitochondrial Proteome from Euglena gracilis

Gene fragmentation and RNA editing without borders: eccentric mitochondrial genomes of diplonemids

Massive mitochondrial DNA content in diplonemid and kinetoplastid protists

Trypanosomatid mitochondrial RNA editing: dramatically complex transcript repertoires revealed with a dedicated mapping tool

Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins

From simple to supercomplex: mitochondrial genomes of euglenozoan protists

Gene Loss and Error-Prone RNA Editing in the Mitochondrion of Perkinsela, an Endosymbiotic Kinetoplastid

Unexpectedly Streamlined Mitochondrial Genome of the Euglenozoan Euglena gracilis

Mitochondrial and nucleolar localization of cysteine desulfurase Nfs and the scaffold protein Isu in Trypanosoma brucei

Dual core processing: MRB1 is an emerging kinetoplast RNA editing complex

Gene fragmentation: a key to mitochondrial genome evolution in Euglenozoa?