It's been a while since I read it, but one of the central ideas is that we construct instances of emotions based on sensory data (from the internal systems that detect and predict our energy needs) in a similar way to how we construct instances of concepts from other sensory modes, e.g. seeing a particular cluster of visual features and concluding "that's a bee". When we feel anger, that's our brain's best guess as to the appropriate interpretation of a bunch of internal measurements -- raised blood pressure, high arousal, etc -- based on context. The same internal state in a different context could be interpreted as a different emotion, so there is no consistent or unique biological fingerprint behind a given emotion.

It's counter-intuitive, but it fits better with what we know about how the nervous system works than the commonly accepted fingerprint idea.

Emotions are the brain's attempt at constructing the concepts that best explain and account for our body's energy budget.

Novelty most likely.