The first music. A campfire. Culture beginning.

Geissenklösterle and Hohle Fels, approximately forty thousand years before present: the oldest documented musical instruments in the archaeological record. Replica acoustics carry ultrasonic harmonics in the twenty-to-eighty kilohertz band — the same band the haemophagic hyoid click uses for echolocation. The dating sits inside the upper-Palaeolithic window in which HHDRV Chapter 2 places phenotype emergence. The compiler proposes, with a hedge the rest of the catalogue does not need, that the flute began as perimeter acoustic defence.

This is not claimed as fact. It is a hypothesis the evidence is consistent with. A purely recreational reading does not explain the harmonic optimisation. Forty thousand years of becoming an instrument is the cultural record of a technology that outlived its first job. HW-0019, the resonator whistle, is the portable descendant that still knows what it is for.