I realize that I am taking up too much space on this Forum, and so I skipped a full explanation. So very briefly: As you probably know, a baby is born with its larynx high in its throat so it is easy to breathe and suck milk simultaneously. At about age two it has descended so that its vocal range is much increased, enabling the child to modulate sounds to the degree required for speech and singing. There is good evidence (but perhaps not overwhelming) that this did not occur in any Homo species prior to sapiens. So, in addition to the “brain programming” I have postulated, these two developments seem to have been necessary before the GLF could have been spread so rapidly through language. Make sense?
Al Leo