Through genetic analysis of 1.75 million people, scientists at the QIMR Berghofer Medical Research Institute and the University of Queensland have brought us one step closer to why people turn out to be lefties.
Researchers identified 48 genetic markers that influence whether a person is right-handed, left-handed, or ambidextrous (equally capable with both hands). 41 of these markers were associated with leftiness and 7 of them were with ambidexterity.
Prof. Sarah Medland explains, "Handedness is one of those things where both genetics and environment play a large role and what we've been able to do is advance the knowledge quite a bit further in the genetics side." She then explains that each of these small variations play a minuscule role on their own, but when they add up, they then begin to have a significant impact.
Of course, researchers didn't test 1.75 million people like that. They utilized data from international biobanks, this is one of the largest studies investigating this field. The study is published in Nature Human Behaviour.
Researchers also emphasize that environmental factors play a bigger role in determining handedness. Medland says, "Something like height is much more strongly genetically-influenced, whereas [for] something like handedness the genetic influences are relatively weak,"
She then adds, "Through training or just through interacting with the environment and using tools that are designed one way or the other, you can actually influence someone's handedness quite a lot."
Ambidexterousness has little to do with left-handedness
Medland also noted that ambidextrousness did not appear to be a middle area between left and right-handedness.
"The results from our study show there was not very much genetic overlap actually between left-handedness and ambidextrousness — it seems like there are different mechanisms going on there."
In concluding the interview she said we require further research to answer why people prefer one hand above the other. She finalized with: "Although we've found 41 variants influencing left-handedness and seven influencing ambidextrousness, there's a lot more out there to find."