Thank you Inma,
So does that mean that even if "siglo" is singular, you can also use the plural? i.e. "a comienzos de..."
does that mean then that you can use the singular "al comienzo de.." if "siglos" was plural?
Do you have any example sentences for these 2 uses?
Do you have any more info on this use? also is this a Peninsular Spain usage? or universally used?
Thank you. Your replies a very appreciated! Nicole