Are You a Southpaw? Raise Your Left Hand!

What determines whether you are right handed or left handed?  Scientists used to think it was your brain.  But new research suggests otherwise.

Only 10 percent of the population is left-handed.  Noteworthy lefties include Barack Obama, Prince William, Bill Gates, Steve Jobs, Mark Zuckerberg and Oprah Winfrey (CBS).  According to, left-handedness:

  • Is twice as common in twins as in the general population
  • May cause you to learn, hear speech and think differently
  • Is associated with health issues including sleep disorder, mental health, pregnancy stress and breast cancer
  • May reduce your risk of ulcers and arthritis

Studies have shown that – contrary to popular opinion – the brains of left-handed and right-handed people are not all that different.  (It’s not as if their right and left brain hemispheres are switched, for instance.)

Recently, a team of researchers studied spinal cord development of fetuses in the womb.  At eight to 12 weeks – before the developing brain and spinal cord have started communicating each other – there are already differences in gene expression between the right and left sides of the spinal cord.

This gene activity causes asymmetrical movement in the fetus’ arms and legs.  And it is probably at this very early stage that you become either right or left handed.

The researchers used an Agilent Bioanalyzer System and RNA Pico Kit to control RNA quality.

Of course, this study begs another question: Why are more people right-handed than left-handed?

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