DarwinTunes is an experiment by scientists at Imperial College London that set out to prove that music can occur naturally through a process of natural selection and sexual reproduction. What they created, after thousands of generations of loops had combined and mutated, turned out to be a collection of songs with everything you'd expect — drums, bass, chord progressions, and melodies — all evolved completely synthetically.
In the experiment, a computer generated random loops of tones which were graded by humans on a scale of musical aesthetics. The higher the grade, the more likely that loop would be to reproduce with highly-rated ones. The scientists found that after only a few hundred generations the grating dissonance of the tones had given way to loops that exhibited the qualities of what we would call music. An important element of the experiment is what effect the environment — a role played by human selection in this case — played on the evolution of the music. Despite never having programmed a specific selector for drum-like sounds, the scientists found that peoples' musical taste forced the algorithm to create rhythmic drum beats.
The scientists proved that music can evolve synthetically, and they hypothesized that the same thing happens to music written by people. This isn't an unfamiliar concept; artwork in general is widely regarded as an evolutionary process. Even the internet has played a role in the genesis of creativity, delivering what is affectionately know as remix culture. Be sure to listen to give the tracks below a listen — they are, after all, the sum of humanity's taste in music.