As for dances without music - I went to see a flamenco exhibition recently - divine it was - there were dances to music ...

... but there were also dances with none. The dancers made their own music with their feet - you could have set your watch by the rhythm - and you could have added music if you felt like it - any musician watching would certainly have been inspired to.

Flamenco is similar to Irish dancing in respect of percussive feet.

I don't know one way or the otheer for sure, but I can easily conceive of a group of people singing airs and dancing reels without instruments.

What instruments would they have been dancing along to?

did the dances exist befor ethe arrival of thee guitar , the fiddle, the bouzouki etc or was everyone sitting around sipping guinness waiting for the musical instrument ship to arrive?

I don't know any better than you - but I contest the view that any part of this debate is logical or safe to assume.