Here is a detailed explanation of the evolutionary purpose of music and rhythmic entrainment in early human societies.
Introduction: The "Auditory Cheesecake" Debate
For decades, evolutionary biologists and anthropologists have debated the origins of music. Charles Darwin himself was puzzled by it, suggesting in The Descent of Man that music was a precursor to language, primarily used for courtship. Conversely, cognitive psychologist Steven Pinker famously dismissed music as "auditory cheesecake"—a delightful byproduct of other evolutionary adaptations (like language and pattern recognition) but biologically useless on its own.
However, modern research increasingly suggests that music and, specifically, rhythmic entrainment (the ability to synchronize body movements to an external beat), provided crucial survival advantages to early humans. These advantages can be categorized into three main pillars: Social Cohesion, Sexual Selection, and Cognitive/Physical Development.
1. Social Cohesion and Group Bonding (The "Social Glue" Hypothesis)
The most widely accepted theory is that music served as a mechanism to bind large groups of people together, fostering cooperation and altruism.
- Synchrony and Endorphins: When humans participate in rhythmic entrainment—singing, drumming, or dancing together—the brain releases a cocktail of neurochemicals, including endorphins, dopamine, and oxytocin. This creates a state of "self-other blurring," where individuals feel less like separate entities and more like a unified whole.
- The Problem of Scale: As early human groups grew larger than the typical primate troop (around 150 members, known as Dunbar’s Number), manual grooming—the primate method of bonding—became too time-consuming. Robin Dunbar suggests that communal singing and dancing evolved as "vocal grooming." It allowed one individual to bond with many others simultaneously.
- Coordinate Action: Rhythmic entrainment trains groups to move together. This capacity for synchronized movement may have translated directly into cooperative tasks essential for survival, such as coordinated hunting, heavy lifting, or organized warfare against rival groups.
2. Sexual Selection (The "peacock's Tail" Hypothesis)
Darwin’s original theory still holds weight among many evolutionary biologists. This hypothesis suggests that musical ability evolved as a signal of fitness to potential mates.
- Honest Signaling: Making music is physically and cognitively demanding. It requires fine motor control, memory, breath control, and stamina. Therefore, a complex song or an energetic dance serves as an "honest signal" of health. If an individual has the surplus energy to sing and dance, they likely have good genes, are free of parasites, and are physically fit.
- Rhythm as a Neurological Test: Rhythmic entrainment is rare in the animal kingdom (found mostly in vocal learners like humans and parrots). Being able to keep a beat requires sophisticated neurological wiring connecting the auditory and motor cortices. A potential mate who could dance well was demonstrating a healthy, high-functioning brain.
3. Parent-Infant Communication (The Lullaby Hypothesis)
Before humans developed complex language, they likely used "Motherese" or infant-directed speech—a melodic, rhythmic way of vocalizing.
- Helpless Infants: Human infants are born prematurely compared to other mammals (due to our large heads and bipedal hips). They are helpless for years. Music became a tool for survival by allowing a parent to soothe an infant remotely.
- Hands-Free Soothing: A mother foraging for food could use a hum or lullaby to reassure a distressed infant without having to stop working to hold them. This increased the parent's productivity and the child's survival rate.
- Emotional Regulation: Rhythmic rocking and singing help regulate an infant's heart rate and emotional state, fostering a secure attachment which is vital for later social development.
4. Cognitive and Perceptual Development
Music may have also served as a training ground for the developing human brain.
- Pattern Recognition: Music relies on patterns, repetition, and prediction. Engaging with music trains the brain to anticipate future events based on past cues—a skill highly transferable to tracking game, predicting weather, or understanding social dynamics.
- Language Acquisition: There is a significant overlap between the neural networks used for music and language. Some theorists, like Steven Mithen, propose a "Hmmmmm" (Holistic, multi-modal, manipulative, musical, mimetic) proto-language. Music may have been the scaffolding upon which complex grammatical language was later built.
5. Intimidation and Defense
Finally, music had a martial application.
- Auditory Illusion of Size: Many animals use loud, low-frequency sounds to appear larger than they are. A group of early humans stomping and chanting in perfect unison creates a massive, singular sound.
- Psychological Warfare: To a predator or a rival human tribe, a loud, synchronized group sounds like a single, giant organism. This rhythmic display signals discipline, unity, and strength, potentially preventing conflict before it starts by intimidating the enemy. The Maori Haka is a modern remnant of this evolutionary utility.
Summary
While we may enjoy music today for aesthetic or emotional reasons, its roots are likely deeply practical.
- It kept us together: By releasing bonding chemicals and enabling group bonding without physical grooming.
- It helped us mate: By advertising physical and neurological health.
- It kept our children alive: By soothing infants and allowing parents to multitask.
- It prepared us for war: By synchronizing movement and intimidating rivals.
Therefore, rhythmic entrainment was not just "cheesecake"; it was a vital technology that helped early humans survive hostile environments and build complex societies.