Competing evolutionary explanations of musical capacity

Why do humans have music? We can understand why language might help us survive and cooperate, but what advantage would the ability to make and enjoy musical sounds provide? Both explanations approach that puzzle. As we read the second, we need to notice what changes about the proposed answer.

A begins by comparing music and language. Both use rhythm and intonation to communicate emotion. We can produce them with our voices or with tools, and we can run them silently through our minds. Those similarities make a connection plausible. They don't make music and language identical.

Brain imaging adds a reason to connect them: both belong to a large neurological system for processing sound. The radio analogy helps. Different programs can run through the same equipment; shared equipment doesn't mean the programs are the same. That's the distinction the explanation needs.

Then A introduces a difference. Most of us actively produce language, but musical performance and composition are less widely mastered. My immediate reaction is that practice might matter: we speak constantly, while we may seldom sing or play an instrument. That's a possible question about the evidence, not the explanation A supplies. A takes the observed primacy of language as a clue about evolution.

The proposed conclusion is that the capacities evolved together as brains grew, but natural selection mainly operated on language. Music came along with it and had little adaptive value of its own. Think of music as a byproduct in this account, rather than a capacity that evolved because it independently improved survival. The shared neurological basis is the support; the inference about their evolutionary history is the conclusion.

B starts with the same puzzle but offers a different answer. Musical capacities could have helped mothers and infants form the emotional bonds needed for care. That would give the capacity an important adaptive use. Now I want to know what evidence connects music to that relationship.

The research describes brief, coordinated exchanges between mothers and infants. Each responds to the other through voice, facial expression, and movement. The exchanges contain variations in pitch, rhythm, timbre, volume, and tempo. This isn't limited to a mother singing a lullaby while a baby listens; both participate in shaping the interaction.

At first, I want to object that interacting isn't the same as making music. But B calls these interactions premusical. The claim concerns the underlying ability to produce and respond to musical elements, not a requirement that infants already perform complete songs. That is the proposed link to the capacity whose origin we're trying to explain.

The last paragraph supplies the survival connection. In the evolutionary sequence B describes, larger brains and a narrowing birth canal led to increasingly premature, helpless infants. Those infants needed longer and better care. The useful contrast is a newborn that needs sustained protection, rather than an animal that can soon stand and walk. If these patterned interactions strengthened the bond that supported care, the capacity behind them could provide a considerable advantage.

So the accounts share some ingredients, including increasing brain size, but use them differently. A links brain growth to language and music evolving together, with language doing the adaptive work. B links the evolutionary changes to infants' need for care and the benefit of musical bonding. I don't have to decide which scientific account is correct. I do need to see the central disagreement: music as a relatively unimportant byproduct versus musical capacity as something with substantial adaptive value.