It’s late and it would take too long to go through each section. They begin by describing what it is about language and language acquisition we must explain. Then at every turn they say something like this:
The question of interest is whether these seemingly modest claims about animal signals help us understand the evolution of our capacity to represent words, including not only their referentiality but their abstractness, their composition via phonology and morphology, and their syntactic roles. Our simple answer is No, for five specific reasons: for animals, (i) acquisition of the entire lexicon is complete by the end of the early juvenile period, and for most species, the sounds or gestures are innately specified; (ii) those sounds and gestures refer, at best, to directly observable objects or events, with great uncertainty about the precise meaning, and no evidence for signals that map to abstract concepts that are detached from sensory experiences; (iii) with a few rare exceptions, individuals only produce single utterances or gestures, never combining signals to create new meaning based on new structures; (iv) utterances are holistic, with no evidence of complex syntactic composition derived from an inventory of discrete morphological elements; (v) the utterances or gestures are not marked by anything remotely resembling grammatical classes, agreement, etc. Given these differences, it is not possible to empirically support a continuity thesis whereby a nonhuman animal form served as a precursor to the modern human form.
They go through the fossil record, concluding that language developed after Neanderthals. I have seen other opinions, at least concerning the intellectual abilities of Neanderthals. Bottom line fossils can’t tell us about the evolution of language.
Molecular biology and neurobiology: We don’t know nearly enough.
Modelling: not grounded in experiment or the internal and external processes that are necessary for language to work.
They close with this:
Should such discoveries from comparative animal behavior, paleontology, neurobiology, and archaeology be made, along with greater depth of understanding of gene-phenotype mapping, it would open the door to more relevant genomics and modeling. These are all big IFs about the nature and possibility of future evidence. Until such evidence is brought forward, understanding of language evolution will remain one of the great mysteries of our species.
They don’t see any evidence. They believe that’s what happened but can’t find evidence of it.
Going to bed now, she said, while herding the dogs to the kennel and then turning out the light.