Why human asymmetry is the secret to our language and our physical existence
In short: Humans appear symmetrical, but we are profoundly asymmetric. From our dominant right hands to the left-brain control of language, this chirality defines us. It even extends to the molecular level, where our very survival depends on the handedness of the molecules that build our bodies and digest our food.
In his 1992 Christmas Lecture, Charles Stirling explored the pervasive nature of asymmetry in both the natural world and human creation. While animals like rats and monkeys lack distinct handedness, humans are predominantly right-handed. This trait is not merely a physical quirk; it is deeply linked to the neurobiology of language, which is typically controlled by the left side of the brain. Researchers have speculated that these two attributes—handedness and language control—might be genetically interconnected, offering a potential path toward understanding the molecular basis of human communication.
This asymmetry is not limited to biology. It is embedded in the artefacts we produce and the conventions we follow. We design clocks to run clockwise and standardize motor axles and gas fittings based on specific handedness. Even our writing systems reflect this: English flows from left to right, while other cultures, such as Jews and Arabs, traditionally write from right to left. These choices emphasize the practical advantages of being asymmetric, allowing us to navigate and organize the world through selective, directional conventions.
At the most fundamental level, our existence relies on chiral molecules. These handed molecules are essential for building our bodies, transmitting genetic information, and digesting food. Our sensory apparatus is itself handed, allowing us to distinguish between different molecular forms, which directly impacts our perceptions of taste and smell. Despite this, the origin of molecular chirality remains an unsolved mystery in science. While we know that genes—themselves composed of handed molecules—control our development and cerebral dominance, the ultimate source of this molecular handedness continues to elude us, marking one of the most significant questions in biology.
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Sources
- Summary by Intellect · source: Narwhals, palindromes and Chesterfield station - Charles Stirling 1992 Christmas Lectures 2/5
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