"Old one about a professional debate" joke

...about the doctor, engineer, and programmer who were debating what the
world's oldest profession was (other than the obvious one)? The doctor
said that medicine was the oldest because the Lord performed surgery in
the removal of Adam's rib. The engineer countered that before that act,
the Lord had performed feats of engineering by creating the earth and
heavens from nothing.
The doctor conceded that the engineer was right and that engineering was
indeed the oldest profession. But then the programmer interjected that
programming was even older. He was chided by both the doctor and the
engineer saying that engineering had to be the oldest, because before the
Lord engineered the earth and heavens, there was nothing, only the Great
Void, only Chaos!
The programmer simply smiled and said:
"Where do you think the Chaos came from?"