There’s a stretch of mangrove along the Selangor River in Malaysia where every night around dusk, something happens that Western naturalists called a myth until 1968. Thousands of Pteroptyx tener fireflies gather on the same trees and begin to flash — not raggedly, not in traveling waves, but in perfect unison. The whole tree pulses on. Off. On. Off. At about three flashes per second. Hugh Smith wrote it up in Science in 1935. The scientific establishment spent the next three decades assuring him that he’d seen a passing flock, a heat shimmer, an optical illusion of his own blinking eyes — anything but what he saw. Because how could a beetle, with a brain barely worth mentioning, without any conductor and without any way to shout “one, two, three,” agree with ten thousand strangers on the downbeat?
The chemistry inside a single firefly is already something to sit with. Luciferin combines with oxygen in the presence of the enzyme luciferase and ATP, and almost 100% of the energy released comes out as photons — no measurable waste heat. An incandescent bulb throws roughly 5% of its input at light and burns the rest into the room. The firefly, running a chemistry older than the dinosaurs, has an efficiency our engineers can’t touch. Biotech labs have hijacked luciferase into a universal reporter gene; you can put it in a mouse’s tumor and watch cancer grow with a camera in the dark. But the interesting thing about the mangrove is not that the lantern is bright. The interesting thing is that this exquisite lantern is being turned on and off in time with everyone else’s, and nobody is telling anybody what time it is.
The math for this was written down in 1975 by Yoshiki Kuramoto for what looked like an unrelated problem: chemical oscillators. He set up a system where each oscillator has its own preferred rhythm and each one nudges its own phase a little toward whatever it senses in its neighbors. Below a critical coupling strength, everyone chugs along on their own and the whole population looks like static. Above it — abruptly, like a phase transition of matter — coherence appears from nothing. The population locks. It is the same equation, with different names on the variables, that governs the pacemaker cells of your heart, the crickets in a Georgia field in August, the neurons that fire together during an epileptic seizure, laser light emerging out of stimulated emission, and (infamously) the London Millennium Bridge in the hour after it opened in 2000, when pedestrians’ small compensating footsteps coupled through the deck and turned a walkway into a synchronized undulation that had to be dampened with 89 tuned mass absorbers. Whenever a lot of little clocks can hear each other, they choose the same time.
But WHY do fireflies bother? For years the assumption was that unison had to be an unfortunate side effect — surely it’s harder for a female to pick out an individual mate when the whole tree flashes at once. In 2010, Andrew Moiseff and Jonathan Copeland at the University of Connecticut set up an experiment in the Great Smoky Mountains with Photinus carolinus, the American synchronous firefly, and found the opposite. When they presented females with artificial LED patterns, the females only responded when the flashes came in unison. Asynchronous flashing produced almost nothing. Against the visual clutter of a forest — moonlit leaves, other flashing species, tourists’ cameras — a synchronized cohort turns out to be easier for the female’s visual system to lock onto, not harder. The unison is the beacon. Coordination doesn’t hide the signal; coordination is the signal.
What I keep circling back to is that no individual firefly is doing anything sophisticated. Each one is running a rule so simple it fits on an index card: saw a flash → speed up my own timer a bit. That’s it. No leader. No shared clock. No message with an intended recipient. The tree is not choreographed; the tree is what remains after ten thousand simple listeners have been adjusting to each other for a few seconds. I think this is quietly one of the most subversive results in modern physics, because we spend so much of our institutional life looking for the conductor. The board of directors. The gene that controls development. The neuron of consciousness. The prime mover. And nature keeps handing us mangroves. The beat is not somewhere in the tree. The beat is what the tree is doing.
— Shelle
Curiosity Lab · ficientdesign.com