Seemed there weren't any (left-handers)
This is in fascinating contrast with non-human primates (ie apes & chimpanzees) for whom there is simply a 50/50 split when it comes to handedness. Whilst it's tempting to immediately jump to the conclusion that language capability and neurological development are somehow implicated, I wonder if it's actually even more fundamental than that.
Within this venerable thread there's a very interesting reference to the dominant hand preference potentially being set at a chorionic/fœtal stage of development, and not actually at some c3yr-old mid toddler stage at all.
My proferred corollary is that humanity learned to 'talk' with their hands and bodies (gesture, dance, poise) long before they began to verbalise. We all know this is inarguably-true, that speech & bodily movement are both inextricably linked, and this is all spinal/midbrain/core as a foundation. And this goes a long way to explain the link between emotional suffering and mental anguish suffered when left-handers are forced to act in a way which is entirely unnatural for them (also: the link between speech loss & movement in stroke sufferers....AND, ipso facto, the way in which foreign language speakers often appear frozen/rigid when trying to speak eg English)
Therefore: might becoming a two-legged creature, with excellent conscious motor control skills for limbs and movement, have in itself driven the development of speech? (which in itself is a cypher for handedness).
Although I try to gather accurate references for citation constantly, I've lost the article on how statistics had been extracted from cave paintings (including the earliest hand-stencil-paint-spit creations) in terms of apparent dominance trends left-versus-right. I'm not sure if this was so presumptuous as to claim a valid detectable preference trend.
I think that left vs right handedness may be a false (or flawed) indicator of mental specialisation/ intrinsic personal style, in that it might show some level of correlation (cf visual/verbal/spatial) but I suspect reality is much more nuanced & complex...yet not necessarily indecipherable forever.