Eli5:what’s the cause of someone being right or left handed? And why the vast majority is right handed?

Question

Eli5:what’s the cause of someone being right or left handed? And why the vast majority is right handed?

In: Biology

Answer 1

I can’t quote the study, but back in 1990’s I read it had something to to with when you were a 3 month old fetus & a surge of testosterone.
That’s why there’s more left handed male people than female.