Exploring a new concept: Cell-autonomous evolutionary adaptation

Many known adaptations found across organisms function at the organismal-level, meaning they require multi-cellular activity to be beneficial. For example, altered erythropoiesis levels in humans at high altitudes or thick layers of fat in animals living in cold climates. However, adaptations may reside in additional levels along a hierarchy from cells to organisms. We propose here another type of adaptation that so far hasn’t been thoroughly addressed. We suggest that, in addition to tissue/organ-level adaptations, an additional layer of evolutionary adaptation may be at work which we term cell-autonomous adaptation (CAA). CAA is an adaptation that occurs in cell-autonomous processes, independent of other cells in the organism. Particularly, if the adapted cell was isolated from the context of the body/organ and exposed to the environmental condition that evoked its evolutionary emergence, the adaptation would still provide benefit to the cell itself.

An example of the distinction between these two adaptation types is manifested in immunity. While the humoral immune system provides services to the entire body, each cell in a mammal is also equipped with cellular immune mechanisms that could adapt to pathogenic challenges.

Interestingly, according to this definition of CAA, we could expect to find convergence or conservation of adaptive genes/pathways relating to CAAs across the diverse biological kingdoms, as it may not be organism-specific. Through a deep literature-review, we explore the importance of this newly defined concept of CAA, particularly in its conservation from humans, to plants and even to unicellular yeast and its implications for multi-cellular evolution.