Complex sentence: Great changes in 6th century encouraged the growth of, and conversion to, Christianity as reflected by the multitude of monasteries which sprang up at mid-century, across Ireland, and by archaeological records of the presence of church sites, Christian burial grounds and holy wells.
Split into simpler sentences: Great changes in 6th century encouraged the growth of, and conversion to, Christianity as reflected by the multitude of monasteries which sprang up at mid-century, across Ireland. This is evidenced by archaeological records of the presence of church sites, Christian burial grounds and holy wells.