Pink Dog

Can anyone explain what humans have been up to here?

Although left-handers currently form about 11% of the population, only about 3% of those born in 1900 were left-handed, a more than three-fold difference which requires explanation. Whether the difference results from social pressure for left-handers to become right-handed, artefacts resulting from response biases that can occur when questionnaires are used, or perhaps a greater mortality of left-handers is still controversial.

McManus and Hartigan, Declining Lefthandedness in Victorian England Seen in the Films of Mitchell and Kenyon, Current Biology, volume 17 number 18, 2007