A pre-K teacher in Oklahoma is making news this week after forcing a left-handed 4-year-old boy to write with his right hand. Regardless, it's surprising that today, in 2015, a teacher would try to force a child to write with his non-dominant hand. Still, the sheer size of the database gave researchers a glimpse into the geography and history of left-handedness that they'd never had before. For starters, they show that rates of left-handedness fell during the late Victorian era, reaching their nadir in the early 1900s. If certain families in certain areas are more likely to pass on left-handedness traits than others, you'd expect to see higher rates of left-handedness in those areas.