If you’re left-handed you're part of a group that makes up about 10% of the population. And this rate of left-handedness has been consistent. Historical and archaeological records, reaching as far back as the Neanderthals, tell us that we’ve had this background rate of left-handedness for quite literally all of human history.   All of human history, that is, except for a small blip between the 19th and 20th centuries.   But before we explore that weird anomaly, one of the most interesting things about this story is how we have come to work out how many left-handers there have been across history.   From studying silhouetted hand prints to analysing paintings, drawings and sculptures, scientists have been able to chart left-handedness back to the Palaeolithic era. Amazingly, tooth striations from Neanderthals help us understand that there have always been lefties. In more recent history, researchers have turned to photos, hospital records and documentaries. Thank goodness for all those old docos that contain endless footage of people waving at the camera. We wave with our dominant hand, so these film reels are an accidental census of left-handedness.   But do you know what's weird about those images of waving crowds from the beginning of the 20th Century? The number of left-handers seems to drop off as they get younger.   Which is where the anomalous data enters. Pulling all the data on left-handers together from cavemen to now, we see there is a pronounced dip in left-handers in the 19th century.   So here's the question - where the hell did all the left-handers go during the 19th century?!   There are three main theories, but these still remain theories: death, fewer babies, or long-standing prejudice whipped up by seriously villainous people. Previous episode mentioned:   The Best Years Of Your Life!   Sources Accident proneness and handedness by WF Daniel and RA Yeo Biased semantics for right and left in 50 Indo-European and non-Indo-European languages, by Wulf Schiefenhovel Handedness and longevity: archival study of cricketers by Aggleton, Bland, Kentridge and Neave Left-handedness and accident-related injury risk by S Coren Left Handed: Bad science and bad attitudes are the problem, not the left hand by Free Thought Blogs National Geographic Smell Survey, by Charles Wysocki and Avery Gilbert New London School Explosion, by Petroleum History Almanac Old books on left-handedness, by Keith Milsom Problems Related to Left-Handedness by KC Garrison #PyrfumeCodefest Twitter Thread by Joel Mainland Retraining left-handers and the aetiology of stuttering: The rise and fall of an intriguing theory, by Howard I Kushner The history and geography of human handedness by IC McManus The surprising geography of American left-handedness by Christopher Ingraham The Sniff Survey, by Boyce Rensberger See omnystudio.com/listener for privacy information.