Linguistic correlates of societal variation: A quantitative analysis.

Traditionally, many researchers have supported a uniformitarian view whereby all languages are of roughly equal complexity, facilitated by internal trade-offs between complexity at different levels, such as morphology and syntax. The extent to which the speakers' societies influence the trade-offs has not been well studied. In this paper, we focus on morphology and syntax, and report significant correlations between specific linguistic and societal features, in particular those relating to exoteric (open) vs. esoteric (close-knit) society types, characterizable in terms of population size, mobility, communication across distances, etc. We conduct an exhaustive quantitative analysis drawing upon WALS, D-Place, Ethnologue and Glottolog, finding some support for our hypothesis that languages spoken by exoteric societies tend towards more complex syntaxes, while languages spoken by esoteric societies tend towards more complex morphologies.

The genomic landscape of mammal domestication might be orchestrated by selected transcription factors regulating brain and craniofacial development.

Domestication transforms once wild animals into tamed animals that can be then exploited by humans. The process entails modifications in the body, cognition, and behavior that are essentially driven by differences in gene expression patterns. Although genetic and epigenetic mechanisms were shown to underlie such differences, less is known about the role exerted by trans-regulatory molecules, notably transcription factors (TFs) in domestication. In this paper, we conducted extensive in silico analyses aimed to clarify the TF landscape of mammal domestication. We first searched the literature, so as to establish a large list of genes selected with domestication in mammals. From this list, we selected genes experimentally demonstrated to exhibit TF functions. We also considered TFs displaying a statistically significant number of targets among the entire list of (domestication) selected genes. This workflow allowed us to identify 5 candidate TFs (SOX2, KLF4, MITF, NR3C1, NR3C2) that were further assessed in terms of biochemical and functional properties. We found that such TFs-of-interest related to mammal domestication are all significantly involved in the development of the brain and the craniofacial region, as well as the immune response and lipid metabolism. A ranking strategy, essentially based on a survey of protein-protein interactions datasets, allowed us to identify SOX2 as the main candidate TF involved in domestication-associated evolutionary changes. These findings should help to clarify the molecular mechanics of domestication and are of interest for future studies aimed to understand the behavioral and cognitive changes associated to domestication.

The gradual coevolution of syntactic combinatorics and categorization under the effects of human self-domestication: a proposal.

The gradual emergence of syntax has been claimed to be engaged in a feedback loop with Human Self-Domestication (HSD), both processes resulting from, and contributing to, enhanced connectivity in selected cortico-striatal networks, which is the mechanism for attenuating reactive aggression, the hallmark of HSD, but also the mechanism of cross-modality, relevant for syntax. Here, we aim to bridge the gap between these brain changes and further changes facilitated by the gradual complexification of grammars. We propose that increased cross-modality would have enabled and supported, more specifically, a feedback loop between categorization abilities relevant for vocabulary building and the gradual emergence of syntactic structure, including Merge. In brief, an enhanced categorization ability not only brings about more distinct categories, but also a critical number of tokens in each category necessary for Merge to take off in a systematic and productive fashion; in turn, the benefits of expressive capabilities brought about by productive Merge encourage more items to be categorized, and more categories to be formed, thus further potentiating categorization abilities, and with it, syntax again. We support our hypothesis with evidence from the domains of language development and animal communication, but also from biology, neuroscience, paleoanthropology, and clinical linguistics.

The human fear paradox turns out to be less paradoxical when global changes in human aggression and language evolution are considered.

Our commentary focuses on the interaction between Grossmann's fearful ape hypothesis (FAH) and the human self-domestication hypothesis (HSDH), also taking into account language acquisition and evolution. Although there is considerable overlap between the two hypotheses, there are also some discrepancies, and our goal is to consider the extent to which HSDH can explain the phenomena identified by FAH without invoking fearfulness as directly adaptive.

The (Co)Evolution of Language and Music Under Human Self-Domestication.

Together with language, music is perhaps the most distinctive behavioral trait of the human species. Different hypotheses have been proposed to explain why only humans perform music and how this ability might have evolved in our species. In this paper, we advance a new model of music evolution that builds on the self-domestication view of human evolution, according to which the human phenotype is, at least in part, the outcome of a process similar to domestication in other mammals, triggered by the reduction in reactive aggression responses to environmental changes. We specifically argue that self-domestication can account for some of the cognitive changes, and particularly for the behaviors conducive to the complexification of music through a cultural mechanism. We hypothesize four stages in the evolution of music under self-domestication forces: (1) collective protomusic; (2) private, timbre-oriented music; (3) small-group, pitch-oriented music; and (4) collective, tonally organized music. This line of development encompasses the worldwide diversity of music types and genres and parallels what has been hypothesized for languages. Overall, music diversity might have emerged in a gradual fashion under the effects of the enhanced cultural niche construction as shaped by the progressive decrease in reactive (i.e., impulsive, triggered by fear or anger) aggression and the increase in proactive (i.e., premeditated, goal-directed) aggression.

Elephants as an animal model for self-domestication.

Humans are unique in their sophisticated culture and societal structures, their complex languages, and their extensive tool use. According to the human self-domestication hypothesis, this unique set of traits may be the result of an evolutionary process of self-induced domestication, in which humans evolved to be less aggressive and more cooperative. However, the only other species that has been argued to be self-domesticated besides humans so far is bonobos, resulting in a narrow scope for investigating this theory limited to the primate order. Here, we propose an animal model for studying self-domestication: the elephant. First, we support our hypothesis with an extensive cross-species comparison, which suggests that elephants indeed exhibit many of the features associated with self-domestication (e.g., reduced aggression, increased prosociality, extended juvenile period, increased playfulness, socially regulated cortisol levels, and complex vocal behavior). Next, we present genetic evidence to reinforce our proposal, showing that genes positively selected in elephants are enriched in pathways associated with domestication traits and include several candidate genes previously associated with domestication. We also discuss several explanations for what may have triggered a self-domestication process in the elephant lineage. Our findings support the idea that elephants, like humans and bonobos, may be self-domesticated. Since the most recent common ancestor of humans and elephants is likely the most recent common ancestor of all placental mammals, our findings have important implications for convergent evolution beyond the primate taxa, and constitute an important advance toward understanding how and why self-domestication shaped humans' unique cultural niche.

Enrichment of self-domestication and neural crest function loci in the heritability of neurodevelopmental disorders.

Self-domestication could contribute to shaping the biology of human brain and consequently the predisposition to neurodevelopmental disorders. Leveraging genome-wide data from the Psychiatric Genomics Consortium, we tested the enrichment of self-domestication and neural crest function loci with respect to the heritability of autism spectrum disorder, schizophrenia (SCZ in East Asian and European ancestries, EAS and EUR, respectively), attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, and Tourette's syndrome (TS). Considering only self-domestication and neural-crest-function annotations in the linkage disequilibrium score regression (LDSC) model, our partitioned heritability analysis revealed statistically significant enrichments across all disorders investigated. The estimates of the heritability enrichments for self-domestication loci were similar across neurodevelopmental disorders, ranging from 0.902 (EAS SCZ, p = 4.55 × 10-20) to 1.577 (TS, p = 5.85 × 10-5). Conversely, a wider spectrum of heritability enrichment estimates was present for neural crest function with the highest enrichment observed for TS (enrichment = 3.453, p = 2.88 × 10-3) and the lowest for EAS SCZ (enrichment = 1.971, p = 3.81 × 10-3). Although these estimates appear to be strong, the enrichments for self-domestication and neural crest function were null once we included additional annotations related to different genomic features. This indicates that the effect of self-domestication on the polygenic architecture of neurodevelopmental disorders is not independent of other functions of human genome.

Abnormal features of human self-domestication in bipolar disorder.

Bipolar disorder (BD) is a severe mental condition characterized by episodes of elevated mood and depression. Being a heritable condition, it features a complex genetic architecture, although it is not still clear how genes contribute to the onset and course of the disease. In this paper, we adopted an evolutionary-genomic approach to this condition, focusing on changes occurred during human evolution as a source of our distinctive cognitive and behavioural phenotype. We show clinical evidence that the BD phenotype can be construed as an abnormal presentation of the human self-domestication phenotype. We further demonstrate that candidate genes for BD significantly overlap with candidates for mammal domestication and that this common set of genes is enriched in functions that are important for the BD phenotype, especially neurotransmitter homeostasis. Finally, we show that candidates for domestication are differentially expressed in brain regions involved in BD pathology, particularly, the hippocampus and the prefrontal cortex, which have been subject to recent changes in our species. Overall, this link between human self-domestication and BD should facilitate a better understanding of the BD etiopathology.

Revisiting the hypothesis of language retrogenesis from an evolutionary perspective.

OBJECTIVE: In this article, we reexamine the hypothesis of language retrogenesis, that is, the assumption that language change over healthy ageing mirrors, albeit inversely, language acquisition by the child. We additionally question whether this inverse pattern can as well be observed at the cognitive and neurobiological levels, and whether it can be informative (and a consequence, in fact) of how language evolved in humans. METHOD: We compare the language strengths and weaknesses signifying language acquisition and its eventual decay in healthy ageing. We further compare age-related cognitive and neurobiological readjustments during each of these two developmental stages, with a focus on brain areas involved in language processing. Finally, we delve into the evolutionary changes experienced by these areas. RESULTS: We present evidence supporting the hypothesis of retrogenesis in two domains of language: the lexicon (lexical access, understanding of nonliteral meanings, and resolution of lexical competition) and syntax (understanding and production of complex sentences). Additionally, we show evidence that the brain areas supporting these complex tasks are late-myelinated in childhood and early-demyelinated during ageing. Finally, we show that some of these areas (such as the inferior frontal gyrus) are phylogenetically newer. CONCLUSIONS: Language acquisition in children and language degradation/loss in healthy ageing follow the principle of retrogenesis, but mostly in domains that are cognitively demanding and that depend on recently evolved brain devices. Putting this differently, the components of language that emerged more recently appear to be more, and earlier, affected during ageing, as well as developed later over childhood. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Delving into the Genetic Causes of Language Impairment in a Case of Partial Deletion of NRXN1.

Introduction: Copy-number variations (CNVs) impacting on small DNA stretches and associated with language deficits provide a unique window to the role played by specific genes in language function. Methods: We report in detail on the cognitive, language, and genetic features of a girl bearing a small deletion (0.186 Mb) in the 2p16.3 region, arr[hg19] 2p16.3(50761778_50947729)×1, affecting exons 3-7 of NRXN1, a neurexin-coding gene previously related to schizophrenia, autism (ASD), attention deficit hyperactivity disorder (ADHD), mood disorder, and intellectual disability (ID). Results: The proband exhibits many of the features commonly found in subjects with deletions of NRXN1, like ASD-like traits (including ritualized behaviors, disordered sensory aspects, social disturbances, and impaired theory of mind), ADHD symptoms, moderate ID, and impaired speech and language. Regarding this latter aspect, we observed altered speech production, underdeveloped phonological awareness, minimal syntax, serious shortage of active vocabulary, impaired receptive language, and inappropriate pragmatic behavior (including lack of metapragmatic awareness and communicative use of gaze). Microarray analyses point to the dysregulation of several genes important for language function in the girl compared to her healthy parents. Discussion: Although some basic cognitive deficit - such as the impairment of executive function - might contribute to the language problems exhibited by the proband, molecular evidence suggests that they might result, to a great extent, from the abnormal expression of genes directly related to language.

An evolutionary account of impairment of self in cognitive disorders.

Recent research has proposed that certain aspects of psychosis, as experienced in, e.g., schizophrenia (SCZ), but also aspects of other cognitive conditions, such as autism spectrum disorders (ASD) and synesthesia, can be related to a shattered sense of the notion of self. In this paper, our goal is to show that altered processing of self can be attributed to an abnormal functioning of cortico-striatal brain networks supporting, among other, one key human distinctive cognitive ability, namely cross-modality, which plays multiple roles in human cognition and language. Specifically, our hypothesis is that this cognitive mechanism sheds light both on some basic aspects of the minimal self and on some aspects related to higher forms of self, such as the narrative self. We further link the atypical functioning in these conditions to some recent evolutionary changes in our species, specifically, an atypical presentation of human self-domestication (HSD) features. In doing so, we also lean on previous work concerning the link between cognitive disorders and language evolution under the effects of HSD. We further show that this approach can unify both linguistic and non-linguistic symptoms of these conditions through deficits in the notion of self. Our considerations provide further support for the hypothesis that SCZ and ASD are diametrically opposed cognitive conditions, as well for the hypothesis that their etiology is associated with recent human evolution, leading to a deeper understanding of the causes and symptoms of these disorders, and providing new cues, which can be used for an earlier and more accurate diagnostics.

Language and Communication Deficits in Chromosome 16p11.2 Deletion Syndrome.

PURPOSE: Chromosome 16p11.2 deletion syndrome (OMIM #611913) is a rare genetic condition resulting from the partial deletion of approximately 35 genes located at Chromosome 16. Affected people exhibit a variable clinical profile, featuring mild dysmorphisms, motor problems, developmental delay, mild intellectual disability (ID), socialization deficits and/or autism spectrum disorder (ASD) traits, and problems with language. Specifically, a precise characterization of the speech, language, and communication (dis)abilities of people with this condition is still pending. METHOD: We used standardized tests and samples of naturalistic speech to provide a longitudinal profile of the speech, language, and communication problems of a boy with Chromosome 16p11.2 deletion syndrome and without ID or ASD. RESULTS: The proband shows impaired expressive abilities as well as problems with receptive language, dysprosody, and ASD-like communication deficits, such as impaired interactive skills, perseverative verbal behavior, overabundance of tangential responses, and lack of metapragmatic awareness and communicative use of gaze, meeting the criteria for social pragmatic communication disorder. CONCLUSIONS: Our results support the view that language and communication impairment should be regarded as one core symptom of Chromosome 16p11.2 deletion syndrome, even without a diagnosis of ASD or ID. Clinical implications of our results, with a focus on therapeutic interventions for children with 16p11.2 deletion syndrome and no ASD or ID, are also discussed. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21561714.

Autism and Williams syndrome: truly mirror conditions in the socio-cognitive domain?

Autism Spectrum Disorders (ASD) and Williams Syndrome (WS) are frequently characterized as mirror conditions in the socio-cognitive domain, with ASD entailing restrictive social interests and with WS exhibiting hypersociability. In this review paper, we examine in detail the strong points and deficits of people with ASD or WS in the socio-cognitive domain and show that both conditions also share some common features. Moreover, we explore the neurobiological basis of the social profile of ASD and WS and found a similar mixture of common affected areas and condition-specific impaired regions. We discuss these findings under the hypothesis of a continuum of the socio-cognitive abilities in humans.

Fish as Model Systems to Study Epigenetic Drivers in Human Self-Domestication and Neurodevelopmental Cognitive Disorders.

Modern humans exhibit phenotypic traits and molecular events shared with other domesticates that are thought to be by-products of selection for reduced aggression. This is the human self-domestication hypothesis. As one of the first types of responses to a novel environment, epigenetic changes may have also facilitated early self-domestication in humans. Here, we argue that fish species, which have been recently domesticated, can provide model systems to study epigenetic drivers in human self-domestication. To test this, we used in silico approaches to compare genes with epigenetic changes in early domesticates of European sea bass with genes exhibiting methylation changes in anatomically modern humans (comparison 1), and neurodevelopmental cognitive disorders considered to exhibit abnormal self-domestication traits, i.e., schizophrenia, Williams syndrome, and autism spectrum disorders (comparison 2). Overlapping genes in comparison 1 were involved in processes like limb morphogenesis and phenotypes like abnormal jaw morphology and hypopigmentation. Overlapping genes in comparison 2 affected paralogue genes involved in processes such as neural crest differentiation and ectoderm differentiation. These findings pave the way for future studies using fish species as models to investigate epigenetic changes as drivers of human self-domestication and as triggers of cognitive disorders.

Communication deficits in a case of a deletion in 7q31.1-q31.33 encompassing FOXP2.

Copy number variants (CNVs) found in individuals with communication deficits provide a valuable window to the genetic causes of problems with language and, more generally, to the genetic foundation of the human-specific ability to learn and use languages. This paper reports on the language and communication problems of a patient with a microduplication in 22q11.23 and a microdeletion in 7q31.1-q1.33 encompassing FOXP2. The proband exhibits severe speech problems and moderate comprehension deficits, whereas her pragmatic abilities are a relative strength, as she uses gestures quite competently to compensate for her expressive issues. This profile is compatible with the deficiencies found in patients with similar CNVs, particularly with people bearing microdeletions in 7q31.1-q31.33.