Complex sentence: Around the start of the 20th century, the American Theodore M. Davis had the excavation permit in the valley, and his team (led mostly by Edward R. Ayrton) discovered several royal and non-royal tombs (including KV43, KV46 and KV57).
Split into simpler sentences: Around the start of the 20th century American explorer Theodore M. Davis had the excavation permit in this valle. His team (led mostly by Edward R. Ayrton) discovered several royal and non-royal tombs (including KV43, KV46 and KV57).