Why your right-handedness and ability to speak are rooted in molecular chemistry
In short: We are surrounded by giant molecules—carbohydrates, proteins, and DNA—that define our existence. These structures are inherently handed, or chiral, a property that dictates everything from how we digest food to the development of our brains. Remarkably, this molecular symmetry may hold the key to understanding our unique human traits.
In his 1992 Christmas Lectures, Charles Stirling explored the fundamental role of chirality, or handedness, in the natural world. These giants, often containing a million atoms or more, are constructed from repeating units. Carbohydrates and proteins serve as the essential scaffolding and energy stores for plants, which animals then break down and reconstruct into glycogen and their own proteins. This process is not merely structural; it is the basis of our biological function.
The blueprint for our entire physical existence is held within DNA, the final handed giant located in our cell nuclei. This code is responsible for constructing our brains, which in turn govern our language and physical handedness. Stirling suggests that these two uniquely human attributes—language and a preference for the right hand—are likely interconnected genetically. This link offers a potential path toward decoding the neurobiology of language and its molecular basis. When this delicate code is disrupted, the consequences can be severe, such as the development of cancer, which chemists combat by targeting the DNA of rogue cells.
Our interaction with these chiral molecules is profound, influencing our sensory perceptions like taste and smell. Because we can distinguish between different handed molecules, it confirms that our own sensory apparatus is itself handed. Despite this deep understanding of molecular chirality, which emerged as a far-reaching chemical realization in the 19th century, a significant mystery remains. While we know that our existence depends on these handed molecules to build our bodies and transmit characteristics to our descendants, the ultimate origin of these chiral molecules in the universe remains an unsolved question in science.
Ultimately, the study of handedness connects the microscopic world of atoms to the macroscopic world of human behavior. By examining the symmetry of ourselves, our fellow creatures, and the artifacts we create, we gain insight into the left-right relationships that define our reality. The ongoing research into how genes control cerebral dominance and handedness continues to be a vital frontier in understanding what truly sets humans apart from other animals.
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- Summary by Intellect · source: In the hands of the giants - Charles Stirling 1992 Christmas Lectures 5/5
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