Soru

Passage A

The human capacity for rhythmic entrainment—the ability to coordinate motor movements precisely with an external periodic auditory stimulus, such as tapping a foot to a musical beat—has long posed an evolutionary puzzle. According to the vocal learning and rhythmic synchronization hypothesis, entrainment is not an independent adaptation directly selected to support musicality or communal dance. Rather, it represents an evolutionary byproduct, or spandrel, arising from the specialized neural architecture originally required for complex vocal mimicry and speech acquisition. Vocal learning demands sophisticated, bidirectional auditory-motor mapping: an organism must perceive an auditory signal, process its fine-grained acoustic features, and rapidly coordinate motor effectors to reproduce that acoustic model.

Proponents of this hypothesis demonstrate that this specialized connectivity between the auditory cortex and motor planning regions inadvertently allows motor circuits to align with regular auditory pulses generally. Cross-species comparative studies provide strong empirical backing for this model. Spontaneous beat entrainment has been documented almost exclusively in vocal learners—including humans, several psittacine bird species (such as cockatoos), and select cetaceans. In contrast, non-human primates, which possess innate, genetically hardwired vocal calls rather than learned vocalizations, consistently fail to exhibit spontaneous, tempo-flexible synchronization to acoustic beats in controlled laboratory trials. Consequently, hypotheses suggesting that rhythmic competence evolved directly to foster ancestral group bonding or social cohesion are neurobiologically unconvincing; rhythm simply hitched a ride on the evolutionary machinery of vocal mimicry.

Passage B

While the vocal-learning hypothesis offers an elegant neuroanatomical explanation for auditory-motor coupling, its claim that entrainment is merely an incidental byproduct of vocal mimicry severely misinterprets the primary evolutionary role of musical behavior. Across human cultures, music functions primarily as a collective, interactive medium. Synchronized group activity—such as communal drumming, chanting, and ritual dance—elevates pain thresholds through endorphin release, enhances cooperative trust among group members, and reinforces intra-group solidarity. These substantial survival advantages strongly suggest that rhythmic synchronization evolved under direct selective pressures favoring interpersonal coordination, coalition signaling, and group defense among ancestral hominins.

Moreover, empirical refutations of the vocal-learning constraint have steadily accumulated. Recent behavioral investigations reveal that when subjects are evaluated in socially rich, ecologically valid contexts rather than isolated laboratory apparatuses, certain non-vocal-learning primates, such as bonobos, demonstrate genuine tempo-matching and collaborative rhythmic entrainment with interactive partners. This finding directly contradicts the assertion that vocal-learning circuitry constitutes an indispensable neurobiological prerequisite for beat tracking. By reducing rhythmic entrainment to an incidental mechanistic byproduct of vocal imitation, mechanistic models overlook the deeply rooted social dynamics of rhythm. Rhythmic synchronization did not merely co-opt vocal pathways; it emerged as an autonomous, socially driven adaptive faculty.

Which one of the following claims regarding rhythmic entrainment represents a point of disagreement between the author of Passage A and the author of Passage B?