Darwin established the foundations of natural selection on his Voyage on HMS beagle in the 19th century.
In the “Descent of Man” he elaborates on natural selection to include sexual selection, which includes studies of bird song.
Bird songs have evolved glamorously to include vast quantities of tension – colourful pitch fluctuations, huge dynamic range, rhythmic modulation and timbral variations.
Through song they ask each other how they are, rejoice in the warm weather, warn of predators and woo with delight.
I sometimes think songs we write are also simply this.