How did vocal communication come to dominate human language? A view from the womb

TL;DR

This paper explores how prenatal exposure to sound may have contributed to the dominance of spoken language over gestural communication in human evolution.

Contribution

The paper highlights prenatal auditory development and in utero learning as novel evolutionary factors in the dominance of vocal communication.

Findings

Fetuses are exposed to and attuned to spoken language in the womb.

Auditory sensitivity develops earlier than visual sensitivity during ontogeny.

The uterine environment is more permeable to sound than to light, favoring vocal learning.

Abstract

Whether human language evolved via a gestural or a vocal route remains an unresolved and contentious issue. Given the existence of two preconditions—a “language faculty” and the capacity for imitative learning both vocally and manually—there is no compelling evidence for gesture being inherently inferior to vocalization as a mode of linguistic expression; indeed, signed languages are capable of the same expressive range as spoken ones. Here, we revisit this conundrum, championing recent methodological advances in human neuroimaging (specifically, in utero functional magnetic resonance imaging) as a window into the role of the prenatal gestational period in language evolution, a critical, yet currently underexplored environment in which fetuses are exposed to, and become attuned to, spoken language. In this Unsolved Mystery, we outline how, compared to visual sensitivity, the ontogenically earlier development of auditory sensitivity, beginning in utero and persisting for several months post-partum, alongside the relative permeability of the uterine environment to sound, but not light, may constitute a small but significant contribution to the current dominance of spoken language.

Whether human language evolved via a gestural or a vocal route remains an unresolved and contentious debate. This Unsolved Mystery discusses evidence suggesting that fetal auditory development and learning in the womb are important evolutionary factors in the dominance of vocal communication.

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