A patch of green grass is full of life and likely to host fungi, bacteria, and insects. Temperature, wind, and sunlight fluctuate constantly. Every biological system—including the food chain and the hardware of DNA replication—is fraught with noise. Given that context, how do living systems establish themselves and work so well?

Take photosynthesis, for example. In certain light conditions, 99 out of 100 photons that enter a plant’s light-harvesting antenna complex excite a chlorophyll electron and make its energy chemically available. That efficiency is possible because of the configuration, or spatial arrangement, of photosynthetic antenna arrays, which consist of pairs of chlorophyll pigments that have been tuned to absorb photons in narrow frequency windows. To help explain the principle that regulates the selection of those frequencies, let’s consider the difficulty of photosynthesis in light of that faced by networks in general.

For a network that experiences rapidly changing environmental conditions...

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