Complex sentence: Fagan notes that, like other great houses in Chaco Canyon, Chetro Ketl was built over an extended period of time, during which the Ancestral Puebloans almost continuously added to the structure, except when diverting their workforce to agriculture.
Split into simpler sentences: Fagan notes that, like other great houses in Chaco Canyon, Chetro Ketl was built over an extended period of time. The Ancestral Puebloans worked on the structure almost continuously, except when diverting their workforce to agriculture.