GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - N3H3UR3479N587Q0K

A cave in Central America was occupied by humans for much of the period from 9,000 to 500 years ago. Archaeological excavations in the cave have discovered remains of food plants at every level of habitation, increasing from fewer than ten food plant species in the earliest (lowest) levels to over 30 species in the latest levels. Clearly, later inhabitants of the cave used a greater variety of plants as food than earlier inhabitants did.