Interesting that we can detect it at very small concentrations. Maybe this is an adaptation from some proto-mammal or even earlier ancestor whose environment ha

Interesting that we can detect it at very small concentrations. Maybe this is an adaptation from some proto-mammal or even earlier ancestor whose environment had few pockets of fertile ground, and detecting this smell was a good way to find food by homing in on high concentrations of plants. (It would not necessarily be just for herbivores. You could be likely to find the plants themselves, but also to find creatures who fed on plants.)