Most people in the world are right handed. Left-handed people have, throughout history, have been thought strange, wrong, or sometimes even evil for preferring to write and do other tasks with the “wrong hand” – to the extent that even in my grandfather’s generations, teachers would slap your hand with a ruler and force you to use your right.

Left-handers have persisted, and have formed a pretty tight bond based on literally nothing else, but why are some people left-handed while the rest of us naturally pick up a crayon with our right?

Science, it turns out, may finally have a real answer.

A new study published in eLife found that it doesn’t have anything to do with our brains or neurological development, as has been posited for some time. Instead, it’s actually stamped on your genetic makeup from the time you’re conceived, like eye color or gender – and it’s embedded in your spine, not your brain.

“Our data suggests a spinal, not a cortical, beginning of hemispheric asymmetries,” the team concluded in their paper.

The researchers were a combined team from Germany, the Netherlands, and South Africa, and were led by biophysicists at Ruhr University Bochum. They carefully monitored gene expression as it took place in the spin cords of fetuses between 8 and 12 weeks gestation.

They detected asymmetry in these proto-spinal cords that has never been detected before, leading them to believe that assumptions about the brain controlling hemispheric activity could be wrong.

These developments take place before the motor cortex, which is responsible for movement, is even wired to the spine – parts of which are responsible for transmitting electrical impulses to the hands, arms, legs, and feet. Research indicates this is also when a person is wired to prefer either their right or left hand.

They also believe they found what causes the symmetry, and it’s not inherited genetic mutations or traits, but environmental factors, instead. Basically, they think we influence our babies’ handedness with influences while in utero.

The team did not put forth any ideas or conclusions on what those environmental/external factors might be, but they did say it’s possible that they alter how enzymes operate around a developing fetus.

Pretty crazy, right?

I guess if anyone out there is looking to have a little leftie (I hear they make more money if they become a major league pitcher!), stay tuned – I’m sure it won’t be long before they figure out the rest.