Complex sentence: His studies of the Sphinx have contributed to a debate on the outer fringes of archaeology regarding the date of the monument and suggest it can be attributed to being built the within the conventionally-defined period, albeit a few centuries earlier than presently agreed.
Split into simpler sentences: His studies of the Sphinx have contributed to a debate on the outer fringes of archaeology regarding the date of the monument. Although his study dates the Sphinx as being built the within the conventionally-defined period, the study suggests that it was built a few centuries earlier than presently agreed.