It is usually thought that we started making art because of “some kind of cultural or demographic change”. Now a scientist is thinking that mutations in the human genome 50,000 years ago could be the cause:

"Professor Klein said that a suite of language and creativity genes, perhaps as few as ten or as many as 10,000, developed as a result of random mutations, giving rise to a new pattern of human culture. "

Hmmm... many random mutations, providing useful changes to humans, occuring all of a sudden, all at once. Perhaps this also happened 12,000 years ago and 5,000 years ago...