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The “putting the baby down” hypothesis: Bipedalism, babbling, and baby slings

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My responses to the observations and criticisms of 26 commentaries focus on the coregulated and affective nature of initial mother/infant interactions, the relationship between motherese and emergent linguistic skills and its implication for hominin evolution, the plausibility of the “putting the baby down” hypothesis, and details about specific neurological substrates that may have formed the basis for the evolution of prelinguistic behaviors and, eventually, protolanguage.

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... Finally, we must touch upon the implications of these hypotheses for the study of infant interactions with adults (Eibl-Eibesfeldt 1989) and their links with mirror neurons (Bråten 2004: Fig. 2, Bråten, Trevarthen 2007, Falk 2004b, Gilissen 2004, Rizzolatti, Arbib 1998, although a thorough analysis must await future publications. The present hypotheses point in several directions that were either unexplored or just glanced on during the debate over Dean Falk's (2004a, 2004b hypothesis concerning the importance of baby-parking before the use of slings for the development of motherese and language. ...
... Finally, we must touch upon the implications of these hypotheses for the study of infant interactions with adults (Eibl-Eibesfeldt 1989) and their links with mirror neurons (Bråten 2004: Fig. 2, Bråten, Trevarthen 2007, Falk 2004b, Gilissen 2004, Rizzolatti, Arbib 1998, although a thorough analysis must await future publications. The present hypotheses point in several directions that were either unexplored or just glanced on during the debate over Dean Falk's (2004a, 2004b hypothesis concerning the importance of baby-parking before the use of slings for the development of motherese and language. ...
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This essay contains two hypotheses: the first postulates that infectious and parasitic conditions in the first baby-carrying devices or "slings" selected for changes in juvenile hair distribution and immuno-resistance, and that a convergence of datable mutations and osteological changes indicate that infants in our lineage adapted to the microenvironment between 1.2 and 2.8 million years ago – with evidence converging towards the older end of that range. Such slings, which might have been first used to carry gleanings, would have surrounded offspring in dangerous pathogens and parasites. Babies whose foetal body baldness had not disappeared would have had an advantage over infants with previously normal body fur, because adults could clean them better – probably resulting in the neotenic extension of the foetal trait. The microenvironment might have selected for the elimination of infectious pathways as well. The inactivation of the CMAH gene, which could have provided a pathway for pathogens associated with ungulate and proboscidean hides to infect infants with diarrhea, is explored as a candidate, and multiple ways of testing the hypothesis are described. The related hypothesis, which is based partly on avian comparisons and milk chemistry, postulates that slings gradually forced adults to focus on the kind of nutrition needed by more slowly maturing infant brains by making their babies more altricial. This might have triggered more scavenging, hunting, and feedback mechanisms that slowly extended the new juvenile hair distribution to adults as part of a whole-body cooling system based on sweat and body baldness while contributing to speciation.
... tightly such that other parts of the body do not move in a way that deforms the skin or the CT receptors; as a result, any response to rocking will be mainly experienced by the inner ear mechanisms as the head is moved through space. Either way, it seems that, in humans at least, this system has been co-opted during recent evolution to underpin the social bonding role of music (a cultural phenomenon) 20,29 , conceivably via an intermediate step in which maternal singing (or humming) functioned to calm infants 55,56 . It is not until they are about 12 months postpartum that human infants reach the same developmental stage achieved at birth by the infants of monkeys and apes (who are not rocked by their mothers) 57 , and it is during this period that human infants are most in need of soothing. ...
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The C-tactile (CLTM) peripheral nervous system is involved in social bonding in primates and humans through its capacity to trigger the brain’s endorphin system. Since the mammalian cochlea has an unusually high density of similar neurons (type-II spiral ganglion neurons, SGNs), we hypothesise that their function may have been exploited for social bonding by co-opting head movements in response to music and other rhythmic movements of the head in social contexts. Music provides one of many cultural behavioural mechanisms for ‘virtual grooming’ in that it is used to trigger the endorphin system with many people simultaneously so as to bond both dyadic relationships and large groups. Changes in pain threshold across an activity are a convenient proxy assay for endorphin uptake in the brain, and we use this, in two experiments, to show that pain thresholds are higher when nodding the head than when sitting still.
... En esta dirección, la música contribuye a la cohesión social y, por lo tanto, aumenta la efectividad de la acción grupal (Bicknell, 2007). Además, existen teorías específicas que defienden que la música surgió de un zumbido o canto destinado a mantener el apego madre-hijo (Falk, 2004). Incluso, se relacionan la música y la ansiedad humana relacionada con la muerte y la consecuente búsqueda de significado (Dissanayake, 2009). ...
... Infant carrying is a rather costly activity among the human species (Altmann & Samuels, 1992), since in Homo sapiens hair has been mostly reduced (Wheeler, 1984(Wheeler, , 1985 and infants have lost their grasping ability (Alemseged et al., 2006). There is little evidence that primates park their infants (Falk, 2004), especially in the early stage of postnatal development, thus setting the baby down was an unlikely strategy used by hominids and mothers were rather forced to carry their babies. In the course of human evolution, there were some tools, which helped to carry an infant, such as slings (Wall-Scheffler, Geiger, & Steudel-Numbers, 2007), but still the protective role during breastfeeding remained important. ...
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There are numerous studies concerning sexual dimorphism in body proportions, but only a few have investigated growth in the relative length of particular segments of the upper and lower limbs during adolescence. The aim of the study is an assessment of sex differences of longitudinal growth in the relative length of the forearm and knee height among adolescents. Sample involved 121 boys and 111 girls, participants of the Wroclaw Growth Study, examined annually between 8 and 18 years of age. Sexual dimorphism in six ratios: forearm length and knee height relatively to: trunk, height, and limb length were analyzed using a two-way analysis of variance with repeated measurements. The sex and age relative to an estimate of maturity timing (3 years before, and after age class at peak height velocity [PHV]) were independent variables. All of the ratios showed significant sex differences in interaction with age relative to age at PHV. The relative length of the forearm, in boys, did not change significantly with the years relative to age at PHV, whereas in girls, was the lowest in the two first age classes and afterward significantly increased just 1 year before and during the adolescent growth spurt, remaining unchanged in further age classes. For relative knee height no clear pattern for sex differences was noticed. It is proposed that relatively longer forearms, particularly in relation to the trunk in girls, could have evolved as an adaptation to more efficient infant carrying and protection during breastfeeding.
... A novel evolutionary theory is offered by Falk (2004a,b) who has proposed that music arose from humming or singing intended to maintain infant-mother attachment. Falk's “putting-down-the-baby hypothesis” suggests that mothers would have profited from putting down their infants in order to make their hands free for other activities. ...
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Why do people listen to music? Over the past several decades, scholars have proposed numerous functions that listening to music might fulfill. However, different theoretical approaches, different methods, and different samples have left a heterogeneous picture regarding the number and nature of musical functions. Moreover, there remains no agreement about the underlying dimensions of these functions. Part one of the paper reviews the research contributions that have explicitly referred to musical functions. It is concluded that a comprehensive investigation addressing the basic dimensions underlying the plethora of functions of music listening is warranted. Part two of the paper presents an empirical investigation of hundreds of functions that could be extracted from the reviewed contributions. These functions were distilled to 129 non-redundant functions that were then rated by 834 respondents. Principal component analysis suggested three distinct underlying dimensions: People listen to music to regulate arousal and mood, to achieve self-awareness, and as an expression of social relatedness. The first and second dimensions were judged to be much more important than the third-a result that contrasts with the idea that music has evolved primarily as a means for social cohesion and communication. The implications of these results are discussed in light of theories on the origin and the functionality of music listening and also for the application of musical stimuli in all areas of psychology and for research in music cognition.
... Based on the favored phonetic forms in the babbling and early words of present day infants, Peter F. MacNeilage (University of Texas at Austin) claimed that three forms of CV-like syllables — coronal stop consonants with front vowels (e.g., " dada " ), dorsal stop consonants with back vowels (e.g., " gogo " ), and bilabial nasal consonants with central or low vowels (e.g., " mama " ) — constitute the fundamental property of speech (MacNeilage & Davis 2000). Following the 'putting the baby down' scenario (Falk 2004), he suggested that parental terms, possessing present day equivalents to the phonetic forms of the first words, are modern copies of language fossils, and that the second words resulted from the requirement of linguistic distinctiveness applied to the parental forms (MacNeilage 2008). Lucie Ménard (UQÀM) found that universal tendencies in sound representations observed in languages could be explained in light of individuals' sensorimotor constraints. ...
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Chapter
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