Nature may have a preferred tempo

From flashing fireflies to human music, many biological rhythms appear to converge on the same rhythmic range

While in Thailand’s mangrove forests filming Pteroptyx malaccae fireflies , known for synchronized flashing, researchers noticed a coincidence: nearby crickets appeared to chirp in time with the flashing insects. “I thought, whoa, could the two be interacting?” says Northwestern University biophysicist Guy Amichay, lead author of a new study on the phenomenon. “It also blew my mind because it’s light versus sound.”

A closer analysis showed that both produced signals at nearly the same tempo—about 2.4 hertz, or roughly 145 beats per minute.

While the tempos’ extreme closeness may indeed be coincidental, a survey of animal communication studies revealed that a broader range—around 0.5 to 4 hertz, or 30 to 240 beats per minute—appeared repeatedly across animals varying enormously in size, from fireflies and fiddler crabs to fish, birds, apes and humans.

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The researchers, who reported their findings in PLOS Biology , also screened 124 recordings from the vast wildlife sound archive xeno-canto and identified 50 species with regular rhythmic signals. These, too, clustered within the same tempo range, with a peak around 180 beats per minute.

“That there might be a common rhythm across a remarkably diverse set of species and communication systems is very intriguing indeed,” says University of Amsterdam music cognition researcher Henkjan Honing, who was not involved in the study. Most popular Western music fits within this range at around 120 beats per minute (2 hertz), he adds.

Many of these species are physically capable of signaling at tempos outside this range, too. So why don’t they? To answer that question, the researchers shifted their attention from signal senders to receivers—because all signals are ultimately processed by nervous systems that are made up of neurons.