Before color, before scent, before nectar, there was heat. Cycads — among the oldest seed plants on Earth, predating flowering plants by over 100 million years — use infrared radiation as their pollination signal.
Male reproductive cones heat themselves using the mitochondrial protein AOX1, emitting infrared radiation at dusk. Pollinating beetles detect this infrared signal using TRPA1 receptors in their antennae — the same gene family that pit vipers use to sense the body heat of prey. When researchers blocked TRPA1 with a chemical inhibitor, beetles stopped responding to warmth. 3D-printed heated replica cones attracted beetles as effectively as real ones.
Across 17 cycad species studied, all followed an identical circadian pattern: male cones heated first, then cooled, then female cones warmed approximately three hours later. The temperature offset creates a directed migration — beetles warmed by male cones go looking for heat again and find the females, carrying pollen.
Every pollination signal humans celebrate — the ultraviolet patterns on petals, the fragrance of flowers, the sugar concentration of nectar — evolved later. Heat was the original advertisement. It required the simplest possible signal (a temperature difference) and the simplest possible detection (a thermoreceptor). The molecular toolkit for infrared detection was repurposed independently by snakes, beetles, and possibly other lineages, all converging on the same gene family.
The oldest solution is often invisible to us because we evolved past it. But it never stopped working.