Proto music: Credible signaling vs. social bonding

Ed Hagen

Department of Anthropology, Washington State University

May 28, 2025

Explicandum: proto-music

The evolution in the human lineage of vocalizations that are:

  • Loud
  • Synchronized
  • Variable

The social bonding hypothesis

  • Primate group cohesion putatively requires grooming
  • Grooming time putatively increases with group size
  • Large human groups required a more efficient “bonding” mechanism
  • Language/gossip, music, dance, and laughter evolved to replace grooming as the mechanism

Against grooming as social bonding

Dunbar’s original data

Against grooming as social bonding

Dunbar’s original data

Against grooming as social bonding

Dunbar’s original data

Grueter et al. (2013)

The social bonding hypothesis

  • In primates, group cohesion putatively requires grooming (grooming probably has social functions, but group cohesion is questionable)
  • Grooming time increases with group size
  • Large human groups required a more efficient “bonding” mechanism
  • Language/gossip, music, dance, and laughter evolved to replace grooming as the mechanism

Against music as social bonding

Natural selection is an optimizing process

Figures modified from Tarr et al. (2014) and Savage et al. (2021)

Against social bonding

Effects are not (necessarily) evolved functions

  • Singing and dancing might (or might not) increase warm feelings, but that is weak evidence that these evolved to do so

  • Petting animals reduces anxiety (Shiloh et al., 2003), but petting animals did not evolve to reduce anxiety

“Social bonding” probably is explained by:

  • Mutual interest (e.g., predator defense)
  • Interdependence (e.g., sexual division of labor)
  • Kinship
  • Reciprocal altruism

The signaling hypothesis

Signals

These evolved to reveal signalers’ private information to receivers to elicit responses in receivers that benefit signalers and (when not deceptive) receivers.

Signals are ubiquitous in nature

  • within organisms
  • within species
  • between species

van der Kooi et al. (2019), Blount et al. (2023)

Signals are ubiquitous in nature

Common functions of animal vocal signals

  • Mate attraction
  • Territorial advertisements
  • Alarm calls
  • Predator signaling
  • Threats
  • Affiliation
  • Contact calls

Coalitional signaling

Signals

  • Territorial advertisements
  • Predator signaling
  • Threats
  • Mate attraction (rare)

Credibility

  • Existence
  • Number
  • Coordination/cooperativeness

Human evolution: Timeline

Human evolution: Late Miocene

Wich & Nunn (2002): Territoriality (resource defense)?

Human evolution: Late Miocene

Data from De Gregorio et al. (2024)

Human evolution: Late Miocene

Small apes duet: monogamous pairs produce highly synchronized song-like calls

Human evolution: Late Miocene

Chimpanzee drumming: population-specific rhythms (Eleuteri et al., 2025)

Human evolution: Late Miocene

Composition and recursion enable tremendous variation:

Human evolution: Pliocene

Human evolution: Pliocene

Predation pressure

Hagen (2022)

Human evolution: Pliocene

Predation pressure

Hagen (2022)

Signaling adaptations to predation pressure

Human evolution: Pliocene

Signaling predator detection and pursuit deterrence (Caro, 2005)

Human evolution: Pliocene

Signaling chemical defense (Howell et al., 2021)

Human evolution: Pliocene

Mesocarnivores: face badges signal pugnacity (Newman et al., 2005)

Human evolution: Pliocene

Baboon threat signal

Human evolution: Pliocene

Predation threat: signaling and coalitional defense

Human evolution: Pleistocene

Cooperative hunting

Human evolution: Pleistocene

Macdonald et al. (2019)

Credible signaling of coalition quality

Credible signaling of coalition quality

Feasting and alliances (Asch & Chagnon, 1970)

Possible signaling contributions to social bonding within and between groups

Group-specfic songs and dances provide information on

  • Identity
  • Commitment
  • Common knowledge

Signaling summary

Loud coordinated vocal chorusing likely has deep roots in human evolution

Miocene ape loud calls

  • Territoriality
  • Contact calls
  • Combinatorial?: variation

Pliocene hominin coalitions

  • Territoriality
  • Predator deterrence (detection)
  • Coordinated?: pugnacity

Pleistocene Homo coalitions

  • Territoriality
  • War songs & dances
  • Feasting & alliances: coalition quality

Vocalizations evolved to provide valuable information (ultimate level), not to increase neurotransmitter levels (proximate level)

Questions?

These slides

References

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