| Humans have vocal folds very similar to those of apes, but we can also precisely control the shape and size of our vocal tract. For powerful high notes, soprano singers match the natural frequencies of the two. But how to find out if gibbons can do the same? Give them some helium. Helium raises the natural frequency just of the vocal tract but not the vocal folds. In helium-huffing gibbons, calls stayed just as piercing because the animals tuned their vocal tracts to match the higher frequencies. In short, gibbons sing soprano all the time. It's not just a primate party trick, this separation between the actual source of the sound and the mechanism of shaping it is something that biologists thought was a result of a long evolutionary process, leading to our finely-controlled speech. But it seems nature came up with the biological equipment for these techniques long before humans headed to the opera. |
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