Adaptation and Exaptation: From Small Molecules to Feathers

Abstract

Evolution works by adaptation and exaptation. At an organismal level, exaptation and adaptation are seen in the formation of organelles and the advent of multicellularity. At the sub-organismal level, molecular systems such as proteins and RNAs readily undergo adaptation and exaptation. Here we suggest that the concepts of adaptation and exaptation are universal, synergistic, and recursive and apply to small molecules such as metabolites, cofactors, and the building blocks of extant polymers. For example, adenosine has been extensively adapted and exapted throughout biological evolution. Chemical variants of adenosine that are products of adaptation include 2′ deoxyadenosine in DNA and a wide array of modified forms in mRNAs, tRNAs, rRNAs, and viral RNAs. Adenosine and its variants have been extensively exapted for various functions, including informational polymers (RNA, DNA), energy storage (ATP), metabolism (e.g., coenzyme A), and signaling (cyclic AMP). According to Gould, Vrba, and Darwin, exaptation imposes a general constraint on interpretation of history and origins; because of exaptation, extant function should not be used to explain evolutionary history. While this notion is accepted in evolutionary biology, it can also guide the study of the chemical origins of life. We propose that (i) evolutionary theory is broadly applicable from the dawn of life to the present time from molecules to organisms, (ii) exaptation and adaptation were important and simultaneous processes, and (iii) robust origin of life models can be constructed without conflating extant utility with historical basis of origins.

Self-empowerment of life through RNA networks, cells and viruses

“…But this does not explain which communicative interactions between RNA networks, viruses and cells lead to new cells, tissues, organs and organisms, because natural laws do not change and adapt but remain fixed (Salmena et al, 2011;Ariza-Mateos & Gomez, 2017;Villarreal & Witzany, 2019). In contrast, communicative rules in generation and combination of signs may change and adapt, which means that biotic innovations may be exapted and coopted for purposes which are different from those which previously emerged (Frenkel-Pinter et al, 2022;Witzany, 2018). The main characteristic of sign-mediated interactions, in contrast to interactions not mediated by signs, is that the proponents may change the rules of sign use for purposes of adaptation, e.g.…”

Self-empowerment of life through RNA networks, cells and viruses

“…But this does not explain which communicative interactions between RNA networks, viruses and cells lead to new cells, tissues, organs and organisms, because natural laws do not change and adapt but remain fixed ( Salmena et al ., 2011 ; Ariza-Mateos & Gomez, 2017 ; Villarreal & Witzany, 2019 ). In contrast, communicative rules in generation and combination of signs may change and adapt, which means that biotic innovations may be exapted and coopted for purposes which are different from those which previously emerged ( Frenkel-Pinter et al ., 2022 ; Witzany, 2018 ) The main characteristic of sign-mediated interactions, in contrast to interactions not mediated by signs, is that the proponents may change the rules of sign use for purposes of adaptation, e.g. dialects in bacteria or even in bee languages, and generate really new sign sequences with really new content ( Ben Jacob et al ., 2004 ; Schauder & Bassler, 2001 ; Witzany, 2014d ; Baluska & Witzany, 2014 ).…”

Common evolutionary origins of the bacterial glycyl tRNA synthetase and alanyl tRNA synthetase

“…bacGlyRS has a deep and convoluted evolutionary history. We infer exaptation relationships (Frenkel-Pinter et al, 2022) between six bacGlyRS domains and six domains of four different RNA-modifying proteins (Figure 2). Exaptation is the co-opting of an existing molecule, domain, trait or system for new function.…”