The left hand of Anna Roentgen. Photoprint from a radiograph by Wilhelm Roentgen, 1895.
Today is International Lefthanders Day, and is marked here by our Wellcome Image of the Month: a sinister-looking X-ray of a left hand. Left-handedness crops up in many fields of science. Amino acids come in left-handed and right-handed forms that are mirror images of each other. This property is called chirality (from the Latin, chiro, for hand).
Living organisms do not use right-handed amino acids, only left-handed forms. Why this asymmetry? There is no apparent biochemical reason but astrobiologists have proposed that amino acids came to Earth in meteorites before life evolved. They have found excess amounts of left-handed molecules compared to right-handed in the space rocks they studied. The implication is that components crucial to the formation of early life on Earth were of ‘alien’ origin.
Our Image of the Month is the result of German physicist Wilhelm Roentgen’s discovery in 1895 of X-rays. It is one the first X-ray images ever produced, and shows the bones of Roentgen’s wife, Anna, who upon viewing her skeleton exclaimed, “I have seen my death!”
X-rays have had a huge impact on science and medicine. They are used as a method of determining molecular structure (see Wellcome Library’s recent blog post featuring Rosalind Franklin’s X-ray crystallography work) and to visualise internal structures of the body in diagnostic medicine.
It’s not only the science that is left-handed, but scientists too. Charles Darwin, Alan Turing and Marie Curie all appear on lists of famous lefties. Arguably the most famous scientist, Albert Einstein, also makes these lists, though there are many photos of him writing with his right hand – perhaps he was ambidextrous?
The famous polymath Leonardo da Vinci is another left-hander, one who was adept at the art of ‘mirror writing’. Thus, in terms of other depictions of the human body, da Vinci could very well have created his own famous anatomical drawings with his left hand.
Left-handedness is often linked to higher than average intelligence, although Professor Chris McManus of University College London refutes this in his 2002 book, Right Hand, Left Hand. McManus is a psychologist who has devoted his career to studying the separate function of the brain’s hemispheres. Those interested in politics might want to draw their own conclusions about intelligence and left-handedness: both Barack Obama and David Cameron are left-handed.
Finally, take a look at this gallery of ‘left-handed’ DNA molecules. The double helix of DNA has become an icon of science, ever since Watson and Crick first described it in 1953. Its double helix is normally right-handed – looking along the axis, it spirals away from the observer in a clockwise direction. But even an icon as distinctive as DNA can be misrepresented: it is rumoured that the artist who designed the new door handles as DNA molecules for a famous scientific institution originally made left-handed helices. They had to be replaced later with the correct, right-handed variety after the mistake was spotted – a case of two lefts not always being right?
Louise Crane, Picture Researcher, Wellcome Images
Image credit: Wellcome Library, London
Wellcome Images is one of the world’s richest and most unique collections, with themes ranging from medical and social history to contemporary healthcare and biomedical science. All our images are available in digital form so please click the link above if you would like to use the picture that features in this post, or to quickly find related ones. Many are free to use non-commercially under the terms of a Creative Commons licence and full details of the specific licence for each image are provided.
Filed under: Wellcome Image of the Month, Wellcome Images Tagged: Alan Turing, Anatomical drawings, B-DNA, DNA, International Lefthanders Day, Left-handedness, Leonardo da Vinci, Marie Curie, Prof Chris McManus, Rosalind Franklin, University College London, Watson and Crick, Wilhelm Roentgen, X-ray, X-ray crystallography, Z-DNA
