I actively look for articles and studies on handedness but they’re not always easy to find. Sometimes I only run across them by accident, like this item from June 2020 on handedness in the womb. It addresses the “nature or nurture” argument about handedness:
About 10.6% of humans are left-handed (Papadatou-Pastou et al., 2020). One of the longstanding questions in scientific research on left-handedness is, at which point in life it actually develops.
One commonly held idea is that it is possible to know for certain whether a child is left-handed or not once he or she starts writing. However, scientific studies show that left-handedness actually develops much earlier to in primary school. In fact, it actually develops before we are even born.
Scientists have investigated left-handedness in unborn babies using real-time ultrasound recording in order to track the movements of their arms and hands in the womb.
For example, one study analyzed real-time ultrasound recordings of 72 fetuses 10 weeks after gestation, focusing on left and right arm movements (Hepper et al., 1998).
[. . .]
The big question about these studies on arm movements and thumb sucking is, whether these behaviors actually predict left- and right-handedness later in life or are unrelated. To answer this question, a longitudinal study tested handedness in 75 children aged between 10 and 12 years in which thumb sucking preferences had been examined using real-time ultrasound recording when they were still fetuses (Hepper et al., 2005).
The results were quite impressive.
Overall, 60 of the children were right-handed as fetuses and all 60 were also right-handed at ages 10 to 12. Thus, a preference to suck the right thumb as a fetus is highly predictive of right-handedness in later life. The remaining 15 children preferred to suck the left thumb as fetuses. In this group, 10 children were left-handers at ages 10 to 12, and 5 were right-handers.
Thus, thumb-sucking preferences as fetus predicted handedness as a child in 70 out of 75 children correctly.
The emphasis at the end is mine.
Once again, correlation does not prove causation, but it does prove this should be studied more. Leave lefty kids alone until the science is in. And even then, leave them alone.