Right Hand, Left Hand
by Chris McManus
Summary
Why is the heart on the left? Why are most people right handed, in every culture and as far back as the tools and cave stencils go, and why, if right handedness is the human rule, do left handers reliably persist at about one in ten? McManus's book takes the apparently small question of handedness and follows it down through every level of nature, and the trip turns out to touch almost everything.
The descent is the structure. Culture first: the vast, nearly universal symbolic load on the two sides, right as sacred and dexterous, left as sinister and gauche, read through languages, religions and etiquette. Then bodies: the rightward loop of the embryonic heart tube, the situs inversus patients whose organs are perfectly mirrored, the molecular machinery, discovered within the decade the book describes, that first breaks the embryo's symmetry. Then brains: language lateralised to the left hemisphere, the genetics of handedness, for which McManus offers his own model of chance and a single gene, and the hard data on what left handedness does and does not correlate with, delivered with a debunker's relish. Then all the way down: the handedness of amino acids and sugars, the universe's own weak force violating parity, and the question of whether life's molecular chirality was chance or necessity.
He writes with donnish humour and a collector's delight in cases, working through asymmetry in brains, bodies, atoms and cultures.
Around four hundred pages.
Best for readers who like one question pursued through physics, embryology, neuroscience and culture without changing books.
Historical Context & Significance
Right Hand, Left Hand won the Aventis Prize in 2003, having already taken the Wellcome Trust Prize, a rare double for a popular science book, and its author is a fitting winner for a book about asymmetry: Chris McManus is professor of psychology and medical education at University College London and edits the field's own journal, Laterality, making this that rare thing, the definitive popular book written by the definitive specialist.
The book distilled three decades of his research programme, including his own model of the genetics of handedness, and its cultural chapters gave it readers far outside science; it has stayed in print as the standard reference whenever handedness surfaces in the press, which is reliably.
McManus collected the prize while continuing the day job of studying medical students.