Most humans are either comfortable with their left or right hand to perform tasks, with a very small minority being ambidextrous. Scientist have always wondered what is the cause of right or left handedness. Observing this scientists reported in 2005 that fetuses will show a hand preference in the womb by sucking the thumb of one hand and that continues after their birth. Although there’s no righty or lefty gene, DNA plays an important role in handedness. However, researchers say that studying the biological differences between lefties and righties could help them to understand this distinction.