Here is a detailed explanation of the evolutionary purpose of music and rhythmic entrainment in early human societies.
Introduction: The "Auditory Cheesecake" Debate
In evolutionary biology, music presents a paradox. Unlike food, sex, or sleep, music does not seem immediately essential for survival. This led the cognitive scientist Steven Pinker to famously describe music as "auditory cheesecake"—a byproduct of other evolved faculties (like language and pattern recognition) that tickles our brain but serves no biological utility.
However, most anthropologists and evolutionary psychologists now reject the "cheesecake" hypothesis. Music appears in every known human culture, suggesting it is a universal human trait. Furthermore, the human brain has specialized neural circuitry for processing pitch and rhythm. This suggests that music and rhythmic entrainment (the ability to synchronize movement to an external beat) played a crucial role in the survival and success of early human groups.
The evolutionary purpose of music can be categorized into four primary theories: Social Cohesion, Sexual Selection, Parent-Infant Bonding, and Cognitive Development.
1. The Social Cohesion Hypothesis (The "Social Glue")
This is the most widely accepted theory regarding the evolutionary function of music. In the harsh environment of the Paleolithic era, solitary humans rarely survived. Survival depended on the group.
- Rhythmic Entrainment as a Synchronization Tool: Humans are the only primates that can spontaneously synchronize their body movements to a beat (entrainment). When a group dances or plays drums together, they are performing a high-cost, coordinated activity.
- Neurochemical Bonding: Group singing and dancing trigger the release of endorphins (pain relief/mild euphoria) and oxytocin (the "bonding hormone"). This chemical cocktail reduces aggression and increases feelings of trust and "oneness" among group members.
- Preparation for Conflict: Many early societies used rhythmic chanting and war dances (similar to the Māori Haka) before conflicts. This served two purposes: it intimidated rivals by displaying a unified, powerful front, and it psychologically primed the group to act as a single unit, increasing their chances of victory.
- Conflict Resolution: Music provided a non-violent mechanism to express emotion and resolve internal group tensions without resorting to physical fighting.
2. The Sexual Selection Hypothesis (The "Peacock's Tail")
Proposed by Charles Darwin himself, this theory suggests that music evolved primarily as a courtship display, similar to the elaborate tail of a peacock or the complex songs of birds.
- Signaling Fitness: Producing music requires a high degree of cognitive complexity, physical coordination, motor control, and memory. In early societies, a distinct singing voice or the ability to drum complex rhythms signaled to potential mates that the individual was healthy, intelligent, and physically fit.
- The "Sexy Son" Hypothesis: If musical ability is attractive, females who mate with musical males will have musical sons who are also attractive to females, perpetuating the genetic line.
- Critique: While music plays a role in courtship, this theory is often criticized because, in most early societies, music was a communal activity performed by everyone (men, women, and children), not just males displaying for females.
3. Parent-Infant Bonding (The Lullaby Theory)
Before language fully developed, early human mothers needed a way to soothe infants while keeping their hands free for foraging or working.
- Motherese: Humans universally speak to infants in "Motherese" or infant-directed speech—a musical, high-pitched, rhythmic way of speaking.
- Survival of Offspring: Human infants are born helpless and require years of care. Lullabies and rhythmic rocking serve to regulate the infant’s emotional state, lower their heart rate, and induce sleep.
- Communication at a Distance: A mother could use vocalizations (humming or singing) to reassure a child that she was nearby without having to hold them, allowing her to gather food. Infants who responded to these musical cues were more likely to remain calm and quiet (avoiding predators) and thus survive.
4. Cognitive and Linguistic Development
Some theorists argue that music was the "scaffolding" for language or a way to train the early brain.
- Musilanguage: Steven Mithen proposed the concept of "Hmmmmm" (Holistic, multi-modal, manipulative, musical, mimetic) communication. He argues that before we had distinct words (syntax), we had a musical protolanguage where sounds conveyed broad emotional meanings. Music and language later split into two separate functions.
- Pattern Recognition: Music relies on recognizing patterns (verse-chorus, rhythmic loops). Practicing music may have sharpened the early human brain’s ability to recognize patterns in nature (e.g., the changing seasons, animal migration tracks), which was vital for hunting and gathering.
The Mechanism: Why Rhythmic Entrainment Matters
The specific ability to lock into a groove—rhythmic entrainment—is the engine that powers these theories.
Research shows that when people move in sync, their "self-other" boundaries blur. They become more altruistic and cooperative toward one another. In early societies, where cooperation was the difference between life and death (in hunting large game or defending against predators), the group that could dance together could work together.
Summary
The evolutionary purpose of music was likely multifunctional. It started perhaps as a way for mothers to bond with infants (Lullaby Theory), evolved into a method for groups to cement their social bonds and coordinate behavior (Social Cohesion), and eventually served as a display of fitness (Sexual Selection).
Far from being "cheesecake," music was likely a vital survival technology—a "social glue" that allowed early humans to form larger, more cooperative, and more stable communities than any other primate species.