Chirality is even seen in plants, depending on the asymmetry of their leaves, and the direction in which they grow.
As an aside, left-handedness has been discriminated against in many cultures for centuries. The Latin word sinistra originally meant “left” but its English descendant “sinister” has taken on meanings of evil or malevolence. The word “right”, meanwhile, connotes correctness, suitability and propriety. Many everyday objects, from scissors to notebooks to can-openers, are designed for right-handed people, and the Latin word for right, dexter, has given us the modern word “dextrous”.
Why is the brain lateralised?
One adaptive advantage of lateralisation is that individuals can perform two tasks at the same time if those tasks are governed by opposite brain hemispheres. Another advantage might be resistance to disease – hand preference in animals is associated with differences in immune function, with right-handed animals mounting a better immune response.
Does it matter if your cat, dog, horse or cow favours one paw (or hoof) over another? Determining laterality – or which side of the brain dominates the other – could change the way domestic animals are bred, raised, trained and used, including predicting which puppies will make the best service dogs, and which racehorses will race better on left- or right-curving tracks.
And even if your dog or cat never clutches a pen, or uses one limb more than the other, just be grateful that they haven’t yet developed opposable thumbs!
This article is dedicated to the memory of Bollo the cat, who inspired this question but has since passed away.