No; it's a perfectly fair question, but I'm feeling a little world-weary just now, and I can see all the same things that always get said in these discussions coming up yet again. That doesn't mean that the question shouldn't be asked. The trouble is that people tend not to answer the question that has been asked, but a different one of their own invention about which they think they know something. See these earlier discussions to get an idea of what I mean:

Oldest Folk

Oldest European Folk Song

Very old music

Earliest known English folk song

There are others, and the subject comes up frequently in the course of other discussions; but it's well past my bed-time; so I only mention those that I found soonest. Also relevant, though a bit specialised, is

A methodology for dating songs etc

Oddly enough, Old MacDonald does seem to have far older roots than does Siul a Run, though of course not in the form seen here (see also Latin form of Old MacDonald's Farm etc).