Stone tools used by our oldest hominin ancestors 2.5 million years ago are believed to have sparked the evolution of human communication (Illustration by Jay Matternes) (news.berkeley.edu)
Berger is arguing that a single hominin ancestor gave rise to two lineages. (slate.com)
So it is possible (though hard to prove) that as our hominin ancestors began walking on two legs rather than four, freeing up their hands to perform new tasks like making tools, they were predisposed to begin using those hands differently. (entrepreneur.com)