1. Left-handedness has sometimes been treated as pathological.

2. What mechanisms, control handedness and keep left-handedness rare?

3. Some historians have suggested that da Vinci's left-handedness added to his genius, because it forced him to think and see in an extraordinary way.

4. Perhaps left-handedness, which makes sense given that we live in a right-handed world.

5. It was my left-handedness , because in China there is a traditional bias against left-handedness and students are forced to write right - handed once they enter school.

6. Interestingly, left-handedness and asthma have also been linked to testosterone and it is now known that men who smoke or drink excessively have reduced levels in their blood.

7. Studies of left-handedness in some one - on - one sports, such as boxing, suggest the same.

8. Proponents argue that fetal exposure to high levels of testosterone could be responsible, and they point out that left-handedness is more common in men than women.

9. Doctors still don't know for sure what causes dyslexia, but they say there is a correlation between left-handedness and the learning disability in many families.

10. Adding weight to the assumption of widespread homochirality is the predominance of left-handedness among amino acids found in meteorites that struck Earth.

11. Some researchers argue there is evidence for cases of "pathological" left-handedness related to brain trauma during birth.

12. A host of studies since the mid-1990s have found common biological traits between gay men, including left-handedness and the direction of hair whorls.

13. However, as more research is undertaken on the causes of left-handedness, attitudes towards left-handed people are gradually changing for the better.

14. "This is really still mysterious," said Clyde Francks, a geneticist and the lead author of a 2007 study in which Oxford University researchers identified a genetic variant linked to left-handedness.

15. Several studies have also examined whether there is any relationship between left-handedness and increased risk of immune disorders.

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16. You're limited by their software, their operating system, their monitor size, even their right- or left-handedness.

17. I'm going to give you some facts and figures about left-handedness.