What did archeologists learn from the packrat nests at Chaco Canyon?

The archaeologists discovered that over time there were fewer and fewer pinion and juniper trees. Then, the trees completely disappeared. Since pinion and juniper were used for firewood and food, that means that humans had to adapt to living in treeless scrub. When trees are cut down, the land is warmed more by the sun, creating dryer, hotter weather. The packrat nests also showed us that game was getting scarce and that people were eating rabbits and mice instead of deer.

Explanation: I completed the test.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.