Language Evolution and Computation Bibliography

Progress in linking between the disparate levels of cognitive description and neural implementation requires explicit, testable, computationally based hypotheses. One such hypothesis is the dendrophilia hypothesis, which suggests that human syntactic abilities rely on our supra-regular computational abilities, implemented via an auxiliary memory store (a ‘stack’) centred on Broca’s region via its connections with other cortical areas. Because linguistic phonology requires less powerful computational abilities than this, at the finitestate level, I suggest that there may be continuity between animal rule learning and human phonology, and that the circuits underlying this provided the precursors of our unusual syntactic abilities.

Artificial grammar learning (AGL) provides a useful tool for exploring rule learning strategies linked to general purpose pattern perception. To be able to directly compare performance of humans with other species with different memory capacities, we developed an AGL task in the visual domain. Presenting entire visual patterns simultaneously instead of sequentially minimizes the amount of required working memory. This approach allowed us to evaluate performance levels of two bird species, kea (Nestor notabilis) and pigeons (Columba livia), in direct comparison to human participants. After being trained to discriminate between two types of visual patterns generated by rules at different levels of computational complexity and presented on a computer screen, birds and humans received further training with a series of novel stimuli that followed the same rules, but differed in various visual features from the training stimuli. Most avian and all human subjects continued to perform well above chance during this initial generalization phase, suggesting that they were able to generalize learned rules to novel stimuli. However, detailed testing with stimuli that violated the intended rules regarding the exact number of stimulus elements indicates that neither bird species was able to successfully acquire the intended pattern rule. Our data suggest that, in contrast to humans, these birds were unable to master a simple rule above the finite-state level, even with simultaneous item presentation and despite intensive training.

This article presents the multiple uses of the concepts of innate and instinctive, by biologists. A broad notion of innate in the sense of having some genetic basis has thus been central to evolutionary approaches to behavior. Lorenz and other ethologists focused on the study of instinct for three practical reasons that include the fact that it justified the discussion and experimental investigation of the adaptive function of behavior, in a Darwinian context, and it allowed ethologists to construct phylogenetic taxonomies of behavior, and thus to explore the evolution of behavior using a comparative method. It signaled a research strategy focused on those aspects of behavior that appear reliably in a species by the time of study, but which avoided the difficult problem of their developmental origins. The developmental psychologist Daniel Lehrman noted that ethologists used the term instinct in multiple different ways. Lorenz and his colleague Niko Tinbergen argued that evolved innate mechanisms could not be avoided in understanding behavior, but that developmental, mechanistic, and evolutionary questions all have a role to play in ethology. Lorenz concluded that learning is impossible without inherited information, but he denied the opposite claim, which was that all instincts entail learning.

Human speech has been investigated with computer models since the invention of digital computers, and models of the evolution of speech first appeared in the late 1960s and early 1970s. Speech science and computer models have a long shared history because speech is a physical signal and can be modeled accurately. This article gives a brief overview of the use of computer models in the study of the evolution of the vocal tract. We also present a critical case study of one model that has been used to study the vocal abilities of Neanderthals. We argue that this study contains subtle but fatal flaws which invalidate the conclusions drawn from the model, illustrating the dangers of applying computer models outside the area for which they have been developed. Future models need to make use of a broader database of anatomical and physiological data from other animals, especially nonhuman primates, to understand the path leading to modern Homo sapiens.

Language, more than anything else, is what makes us human. It appears that no communication system of equivalent power exists elsewhere in the animal kingdom. Any normal human child will learn a language based on rather sparse data in the surrounding world, while even the brightest chimpanzee, exposed to the same environment, will not. Why not How, and why, did language evolve in our species and not in others Since Darwin's theory of evolution, questions about the origin of language have generated a rapidly-growing scientific literature, stretched across a number of disciplines, much of it directed at specialist audiences. The diversity of perspectives from linguistics, anthropology, speech science, genetics, neuroscience and evolutionary biology can be bewildering. Tecumseh Fitch cuts through this vast literature, bringing together its most important insights to explore one of the biggest unsolved puzzles of human history.

- Explores a fascinating puzzle
- how did we humans develop the ability to speak?
- Unlike previous books, it combines insights from many different disciplines
- A useful glossary of terms helps readers from all backgrounds understand the concepts

Contents
Introduction; Part I. The Lay of the Land: 1. Language from a biological perspective; 2. Evolution; 3. Language; 4. Animal cognition and communication; Part II. Meet the Ancestors: 5. Meet the ancestors; 6. The last common ancestor; 7. The hominid fossil record; Part III. The Evolution of Speech: 8. The evolution of the human vocal tract; 9. The evolution of vocal control; 10. Modelling the evolution of speech; Part IV. Phylogenetic Models of Language Evolution: 11. Language evolution before Darwin; 12. Lexical protolanguage; 13. Gestural protolanguage; 14. Musical protolanguage; 15. Conclusions & prospects.

Human language and social cognition are closely linked: advanced social cognition is necessary for children to acquire language, and language allows forms of social understanding (and, more broadly, culture) that would otherwise be impossible. Both `language' and `social cognition' are complex constructs, involving many independent cognitive mechanisms, and the comparative approach provides a powerful route to understanding the evolution of such mechanisms. We provide a broad comparative review of mechanisms underlying social intelligence in vertebrates, with the goal of determining which human mechanisms are broadly shared, which have evolved in parallel in other clades, and which, potentially, are uniquely developed in our species. We emphasize the importance of convergent evolution for testing hypotheses about neural mechanisms and their evolution.

Because language doesn't fossilize, it is difficult to unambiguously time the evolutionary events leading to language in the human lineage using traditional paleontological data. Furthermore, techniques from historical linguistics are generally seen to have an insufficient time depth to tell us anything about the nature of pre- modern-human language. Thus hypotheses about early stages of language evolution have often been seen as untestable ''fairy tales''. However, the discovery of human-unique alleles, associated with different aspects of language, offers a way out of this impasse. If an allele has been subjected to powerful selection, reaching or nearing fixation, statistical techniques allow us to approximately date the timing of the selective sweep. This technique has been employed to date the selective sweep associated with FOXP2, our current best example of a gene associated with spoken language. Although the dates themselves are subject to considerable error, a series of different dates, for different language-associated genes, provides a powerful means of testing evolutionary models of language if they are explicit and span the complete time period between our separation from chimpanzees to the present. We illustrate the potential of this approach by deriving explicit timing predictions from four contrasting models of ''protolanguage.'' For example, models of musical protolanguage suggest that vocal control came early, while gestural protolanguage sees speech as a late addition. Donald's mimetic protolanguage argues that these should appear at the same time, and further suggests that this was associated with Homo erectus. Although there are too few language-associated genes currently known to resolve the issue now, recent progress in the genetic basis for dyslexia and autism offers considerable hope that a suite of such genes will soon be available, and we offer this theoretical framework both in anticipation of this time, and to spur those developing hypotheses of language evolution to make them explicit enough to be integrated within such a hypothesis-testing framework.

Historical language change (), like evolution itself, is a fact; and its implications for the biological evolution of the human capacity for language acquisition () have been ably explored by many contemporary theorists. However, Christiansen & Chater's (C&C's) revolutionary call for a replacement of phylogenetic models with glossogenetic cultural models is based on an inadequate understanding of either. The solution to their lies before their eyes, but they mistakenly reject it due to a supposed Gene/;culture co-evolution poses a series of difficult theoretical and empirical problems that will be resolved by subtle thinking, adequate models, and careful cross-disciplinary research, not by oversimplified manifestos.

Evolutionary theorists since Darwin have been interested in the parallels and interactions between biological and cultural evolution. Recent applications of empirical techniques originally developed to analyze molecular genetic data to linguistic data offer new insights into the historical evolution of language, revealing fascinating parallels between language change and biological evolution. This work offers considerable potential toward unified theories of genetic and cultural change.

Studies of the biology of music (as of language) are highly interdisciplinary and demand the integration of diverse strands of evidence. In this paper, I present a comparative perspective on the biology and evolution of music, stressing the value of comparisons both with human language, and with those animal communication systems traditionally termed 'song'. A comparison of the 'design features' of music with those of language reveals substantial overlap, along with some important differences. Most of these differences appear to stem from semantic, rather than structural, factors, suggesting a shared formal core of music and language. I next review various animal communication systems that appear related to human music, either by analogy (bird and whale 'song') or potential homology (great ape bimanual drumming). A crucial comparative distinction is between learned, complex signals (like language, music and birdsong) and unlearned signals (like laughter, ape calls, or bird calls). While human vocalizations clearly build upon an acoustic and emotional foundation shared with other primates and mammals, vocal learning has evolved independently in our species since our divergence with chimpanzees. The convergent evolution of vocal learning in other species offers a powerful window into psychological and neural constraints influencing the evolution of complex signaling systems (including both song and speech), while ape drumming presents a fascinating potential homology with human instrumental music. I next discuss the archeological data relevant to music evolution, concluding on the basis of prehistoric bone flutes that instrumental music is at least 40,000 years old, and perhaps much older. I end with a brief review of adaptive functions proposed for music, concluding that no one selective force (e.g., sexual selection) is adequate to explaining all aspects of human music. I suggest that questions about the past function of music are unlikely to be answered definitively and are thus a poor choice as a research focus for biomusicology. In contrast, a comparative approach to music promises rich dividends for our future understanding of the biology and evolution of music.

For many years the evolution of language has been seen as a disreputable topic, mired in fanciful ``just so stories'' about language origins. However, in the last decade a new synthesis of modern linguistics, cognitive neuroscience and neo-Darwinian evolutionary theory has begun to make important contributions to our understanding of the biology and evolution of language. I review some of this recent progress, focusing on the value of the comparative method, which uses data from animal species to draw inferences about language evolution. Discussing speech first, I show how data concerning a wide variety of species, from monkeys to birds, can increase our understanding of the anatomical and neural mechanisms underlying human spoken language, and how bird and whale song provide insights into the ultimate evolutionary function of language. I discuss the ``descended larynx'' of humans, a peculiar adaptation for speech that has received much attention in the past, which despite earlier claims is not uniquely human. Then I will turn to the neural mechanisms underlying spoken language, pointing out the difficulties animals apparently experience in perceiving hierarchical structure in sounds, and stressing the importance of vocal imitation in the evolution of a spoken language. Turning to ultimate function, I suggest that communication among kin (especially between parents and offspring) played a crucial but neglected role in driving language evolution. Finally, I briefly discuss phylogeny, discussing hypotheses that offer plausible routes to human language from a non-linguistic chimp-like ancestor. I conclude that comparative data from living animals will be key to developing a richer, more interdisciplinary understanding of our most distinctively human trait: language.

In this response to Pinker and Jackendoff's critique, we extend our previous framework for discussion of language evolution, clarifying certain distinctions and elaborating on a number of points. In the first half of the paper, we reiterate that profitable research into the biology and evolution of language requires fractionation of ``language'' into component mechanisms and interfaces, a non-trivial endeavor whose results are unlikely to map onto traditional disciplinary boundaries. Our terminological distinction between FLN and FLB is intended to help clarify misunderstandings and aid interdisciplinary rapprochement. By blurring this distinction, Pinker and Jackendoff mischaracterize our hypothesis 3 which concerns only FLN, not ``language'' as a whole. Many of their arguments and examples are thus irrelevant to this hypothesis. Their critique of the minimalist program is for the most part equally irrelevant, because very few of the arguments in our original paper were tied to this program; in an online appendix we detail the deep inaccuracies in their characterization of this program. Concerning evolution, we believe that Pinker and Jackendoff's emphasis on the past adaptive history of the language faculty is misplaced. Such questions are unlikely to be resolved empirically due to a lack of relevant data, and invite speculation rather than research. Preoccupation with the issue has retarded progress in the field by diverting research away from empirical questions, many of which can be addressed with comparative data. Moreover, offering an adaptive hypothesis as an alternative to our hypothesis concerning mechanisms is a logical error, as questions of function are independent of those concerning mechanism. The second half of our paper consists of a detailed response to the specific data discussed by Pinker and Jackendoff. Although many of their examples are irrelevant to our original paper and arguments, we find several areas of substantive disagreement that could be resolved by future empirical research. We conclude that progress in understanding the evolution of language will require much more empirical research, grounded in modern comparative biology, more interdisciplinary collaboration, and much less of the adaptive storytelling and phylogenetic speculation that has traditionally characterized the field.

In this paper, I briefly review some comparative data that provide an empirical basis for research on the evolution of music making in humans. First, a brief comparison of music and language leads to discussion of design features of music, suggesting a deep connection between the biology of music and language. I then selectively review data on animal ``music.'' Examining sound production in animals, we find examples of repeated convergent evolution or analogy (the evolution of vocal learning of complex songs in birds, whales, and seals). A fascinating but overlooked potential homology to instrumental music is provided by manual percussion in African apes. Such comparative behavioral data, combined with neuroscientific and developmental data, provide an important starting point for any hypothesis about how or why human music evolved. Regarding these functional and phylogenetic questions, I discuss some previously proposed functions of music, including Pinker's ``cheesecake'' hypothesis; Darwin's and others' sexual selection model; Dunbar's group ``grooming'' hypothesis; and Trehub's caregiving model. I conclude that only the last hypothesis receives strong support from currently available data. I end with a brief synopsis of Darwin's model of a songlike musical ``protolanguage,'' concluding that Darwin's model is consistent with much of the available evidence concerning the evolution of both music and language. There is a rich future for empirical investigations of the evolution of music, both in investigations of individual differences among humans, and in interspecific investigations of musical abilities in other animals, especially those of our ape cousins, about which we know little.

Understanding developmental and evolutionary aspects of the language faculty requires comparing adult languages users' abilities with those of non-verbal subjects, such as babies and non-human animals. Classically, comparative work in this area has relied on the rich theoretical frameworks developed by linguists in the generative grammar tradition. However, the great variety of generative theories and the fact that they are models of language specifically makes it difficult to know what to test in animals and children lacking the expressive abilities of normal, mature adults. We suggest that this problem can be mitigated by tapping equally rich, but more formal mathematical approaches to language.

From a biologist's perspective, language has its own particular design features. It is present in virtually all humans, appears to be mediated by dedicated neural circuitry, exhibits a characteristic pattern of development, and is grounded in a suite of constraints that can be ...

We argue that an understanding of the faculty of language requires substantial interdisciplinary cooperation. We suggest how current developments in linguistics can be pro.tably wedded to work in evolutionary biology, anthropology, psychology, and neuroscience. We submit that a distinction should be made between the faculty of language in the broad sense (FLB)and in the narrow sense (FLN). FLB includes a sensory-motor system, a conceptual-intentional system, and the computational mechanisms for recursion, providing the capacity to generate an in.nite range of expressions from a finite set of elements. We hypothesize that FLN only includes recursion and is the only uniquely human component of the faculty of language. We further argue that FLN may have evolved for reasons other than language, hence comparative studies might look for evidence of such computations outside of the domain of communication (for example, number, navigation, and social relations).

The evolution of speech can be studied independently of the evolution of language, with the advantage that most aspects of speech acoustics, physiology and neural control are shared with animals, and thus open to empirical investigation. At least two changes were necessary prerequisites for modern human speech abilities: (1) modification of vocal tract morphology, and (2) development of vocal imitative ability. Despite an extensive literature, attempts to pinpoint the timing of these changes using fossil data have proven inconclusive. However, recent comparative data from nonhuman primates have shed light on the ancestral use of formants (a crucial cue in human speech) to identify individuals and gauge body size. Second, comparative analysis of the diverse vertebrates that have evolved vocal imitation (humans, cetaceans, seals and birds) provides several distinct, testable hypotheses about the adaptive function of vocal mimicry. These developments suggest that, for understanding the evolution of speech, comparative analysis of living species provides a viable alternative to fossil data. However, the neural basis for vocal mimicry and for mimesis in general remains unknown.