Human evolution; our unique speech mechanism (Introduction)

by David Turell @, Sunday, June 09, 2019, 02:11 (131 days ago) @ David Turell

It exists only in us:

https://inference-review.com/article/the-siege-of-paris

The human language faculty is a species-specific property, with no known group differences and little variation. There are no significant analogues or homologues to the human language faculty in other species. The notion of a species-specific biological trait is itself unremarkable. Species-specific traits are essential to the very definition of a species, at least for multicellular animals requiring reproductive isolation, and species specificity is both widespread and expected according to conventional evolutionary theory. Still, an expectation, it is important to stress, is not yet an explanation.

Why only us? Why indeed.

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Every human language is a finite computational system generating an infinite array of hierarchically structured expressions. This is the basic property (BP) of language. Every structured expression has a definite semantic interpretation and can be expressed by some sensory modality—speech when possible, gesture when not. The BP is best explained, we argued, as the expression of an underlying computational system,

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In Why Only Us, we argued against the thesis that FOXP2 is the gene for language. FOXP2 functions as part of the system for externalizing language to the sensory-motor interface, and many aspects of externalization are not specific to human beings. Citing comparative avian work by Andreas Pfenning et al., we demonstrated that many of the systems for vocal learning and production must have been in place before the emergence of language.

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Elizabeth Atkinson et al. carefully reexamined FOXP2 together with the intronic regions that might have been involved in a selective sweep. They found that human-specific DNA and amino acid variations matched those of Neanderthals or Denisovans but not other non-human primates.

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How far back does language go? There is no evidence of significant symbolic activity before the appearance of anatomically modern humans 200 thousand years ago (kya). The South African Blombos cave site contains abstract patterns using ochre crayon on silcrete. These have been dated to approximately 80 kya. There is no doubt that these patterns, which represent the earliest known drawings, were executed by anatomically modern humans.

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Recent genomic work has refined our claims about symbolic activity. The emergence of language occurred earlier than we thought, and certainly earlier than we suggested. The relevant research is drawn from the detailed genomic sequencing of human subpopulations, and establishes that between 200 kya and 125 kya, the San people in Southern Africa became genomically separated from other human populations. The San are alive today; their ancestors presumably shared the human language faculty. The BP must have emerged sometime between 300 and 200 kya.

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He concludes that the language faculty emerged with Homo sapiens, or shortly thereafter, but externalization in one form or another must have been a later development, and quite possibly involved little or no evolutionary change. (mybold)

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For all that, the chasm between phenotype, algorithm, and neural implementation remains just that—a chasm. We do not yet understand the space of algorithms that might inform, or guide, the BP....it is also true that we have no direct link between the genome and any complex phenotype—say, genes and walking. This remains one of the great scientific challenges, one more thing that we cannot yet puzzle out.

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There is no evidence that great apes, however sophisticated, have any of the crucial distinguishing features of language and ample evidence that they do not. Claims made in favor of their semantic powers, we might observe, are wrong. Recent research reveals that the semantic properties of even the simplest words are radically different from anything in animal symbolic systems.

Comment: Note my bold. Anatomy was fully developed before sapiens speech appeared. Anatomic form first, then function. Note, one of the authors is Noam Chomsky


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