Neal Shepperson asks, "What determines left or right handedness and why are us lefties in the minority?"
One in ten people are left-handed, but where does this ratio come from and when did it appear in our evolutionary past?
Hannah talks to primatologist Prof Linda Marchant from Miami University about why Neanderthal teeth could hold the answer.
Prof Chris McManus from University College London tells Adam about his quest to track down the genes responsible for whether we're right or left handed.
But does left-handedness affect people’s brains and behaviour? Some researchers point to a link between left-handedness and impairments like autism or dyslexia. Others claim that lefties are more creative and artistic.
So where does the answer lie? The team consults Professors Sophie Scott, Chris McManus and Dorothy Bishop to find out the truth about left-handers.
If you have any Curious Cases for the team to investigate please email curiouscases@bbc.co.uk
Picture: Left handed child, credit: Diarmid Courreges/AFP/Getty Images
Presenter: Adam Rutherford & Hannah Fry
Producer: Michelle Martin.