I feel like this quickly glosses over the hypothesis that gestural language evolved first, or that they evolved simultaneously with significantly more sophisticated gestural behavior evolving earlier. I believe gestural language is much older than 500 ka (up to, let’s say, 2 Ma), which is consistent with the fossil evidence on vocalization adaptations.
It’s undeniable that some of the cognitive changes that occurred during human evolution affected motivation; in fact, in my view, I think proto-curiosity and proto-patience would have been favored by selection quite early. On the other hand, in my view, sustainable, scalable joint attention and behaviorally modern imitation learning (e.g. overimitation) are more complex and would have required more than just motivational changes. In particular, I don’t believe that most of the linguistic capability gap between chimps and humans can be explained as ‘motivational hobbling.’
F5 in Old World monkeys is very likely homologous to Broca’s area in humans, and although the gross neuroanatomy of humans and nonhuman primates is highly conserved, there are notable differences between the fine neuroanatomy of F5 in macaques and Broca’s area. Chimp F5 has intermediate features, but the evidence here is limited since we don’t do single-cell recordings in great apes anymore.
My own explanation for why there does not appear to be a derived gross language organ in humans is that F5 and Broca’s area both generate and interpret hierarchical act strings as such. Such a scheme would have several continuous parameters responsive to selection, including hierarchy depth, hierarchy breadth, goal maintenance duration and goal switching speed. I think at various scales this system is general enough to generate and interpret (i.e. socially learn) act strings for flintknapping, gestural and vocal language, controlled fire use, etc. I think this explains why chimps can also learn to knap, but their tools are worse than habilis, and I think it also explains many of the specific linguistic limitations observed in apes using sign and lexigrams.
I feel like this quickly glosses over the hypothesis that gestural language evolved first, or that they evolved simultaneously with significantly more sophisticated gestural behavior evolving earlier. I believe gestural language is much older than 500 ka (up to, let’s say, 2 Ma), which is consistent with the fossil evidence on vocalization adaptations.
It’s undeniable that some of the cognitive changes that occurred during human evolution affected motivation; in fact, in my view, I think proto-curiosity and proto-patience would have been favored by selection quite early. On the other hand, in my view, sustainable, scalable joint attention and behaviorally modern imitation learning (e.g. overimitation) are more complex and would have required more than just motivational changes. In particular, I don’t believe that most of the linguistic capability gap between chimps and humans can be explained as ‘motivational hobbling.’
F5 in Old World monkeys is very likely homologous to Broca’s area in humans, and although the gross neuroanatomy of humans and nonhuman primates is highly conserved, there are notable differences between the fine neuroanatomy of F5 in macaques and Broca’s area. Chimp F5 has intermediate features, but the evidence here is limited since we don’t do single-cell recordings in great apes anymore.
My own explanation for why there does not appear to be a derived gross language organ in humans is that F5 and Broca’s area both generate and interpret hierarchical act strings as such. Such a scheme would have several continuous parameters responsive to selection, including hierarchy depth, hierarchy breadth, goal maintenance duration and goal switching speed. I think at various scales this system is general enough to generate and interpret (i.e. socially learn) act strings for flintknapping, gestural and vocal language, controlled fire use, etc. I think this explains why chimps can also learn to knap, but their tools are worse than habilis, and I think it also explains many of the specific linguistic limitations observed in apes using sign and lexigrams.