Complex sentence: The cabbage-tree was planted by agriculturalists on the complex system of terraces built high up in the Ethiopian Highlands, where they became domesticated and were bred to improve productivity, the taste of their leaves, and the size of their seeds.
Split into simpler sentences: The cabbage-tree was planted by agriculturalists on the complex system of terraces built high up in the Ethiopian Highlands. Here they became domesticated and were bred to improve productivity, the taste of their leaves and the size of their seeds.