On Handedness in Animals and Plants

Structural and functional asymmetries are traceable in every form of life and, at all cases, are a phenomenon of homology. Functionally speaking, the division of labour between the two halves of the brain is a basic characteristic of the nervous system that arose even before the appearance of vertebrates. The most prominent consequence of this specialization in humans and animals is handedness. Even if handedness is far more commonly associated with the presence of a nervous system, it is also observed in aneural organism such as plants. To date, little is known regarding the possible functional significance of handedness in plants, and many questions remain open (among these, whether it reflects a generalized behavioural asymmetry). Here, we propose a comparative perspective to the study of handedness, including plants, by taking advantage of the experimental models and paradigms already used to study laterality in humans and various animal species. By taking this approach, we aim to enrich our knowledge on the concept of handedness across natural kingdoms.