Classification should reflect evolutionary relationships
In his 1859 book On the Origin of Species, Charles Darwin said “probably all the organic beings which have ever lived on this earth have descended from some one primordial form”
This “one primordial form” is now often referred to as LUCA (the last universal common ancestor).
Organisms that share a recent ancestor are evolutionary more closely related. These organisms will have base sequences in their DNA that are more similar to each other than to organisms that share only a distant ancestor.
In the music class (classification) the human and the chimp sat close together and had bass (DNA bases) guitars that were very similar. But the fish in the distance (distant) had a very different bass drum.