Science Quote by Peter R. Grant

In one clean sentence, Grant is doing what great field biologists do: turning an awkward exception into the sharpest proof. Most of the time, traits travel in packs. A bird with a certain beak shape tends to sing a certain song; ecology, development, and learning mesh into a predictable bundle. That tidy association can make mate choice look simpler than it is, because you can’t tell whether birds are “choosing song” or “choosing shape” when the two reliably co-occur.

Grant’s specific intent is methodological and quietly polemical. He’s arguing that morphology isn’t just background scenery to the more glamorous signals like song. It has its own causal force in sexual selection. The key phrase is “revealed by the rare instances”: he’s spotlighting natural “experiments” where the normal coupling breaks. When a bird’s body doesn’t match its song, mate choice decisions become legible; preference can be attributed rather than guessed. It’s a scientist’s version of pulling apart two sticky pages to see what was printed on each.

The subtext is a warning against seductive correlations. If you only study the typical cases, you risk mistaking a linked package for a single driver and telling an overly neat evolutionary story. Contextually, this sits squarely in the Grants’ Galapagos finch tradition, where small deviations - mislearned songs, hybrid morphologies, odd developmental outcomes - become windows into speciation itself. The sentence’s cool tone masks a high-stakes claim: reproductive isolation can hinge on bodies as much as on voices, and evolution often announces itself first in the anomalies we’re tempted to discard.