The reason Old-World monkeys can’t talk, the researchers say, is not because of the anatomy of their vocal tracts but because they don’t have the necessary neural structures.
Another theory is that neurological changes may have been the driver of the ability to produce speech. That’s the conclusion of the authors of the 2019 paper. The reason Old-World monkeys can’t talk, the researchers say, is not because of the anatomy of their vocal tracts but because they don’t have the necessary neural structures. The neurological language theory seems to be holding up better than LDT.