Follow-up for talk about existential risk and collapse of civilization:

Zimbabwe civilization shifted not collapsed

The Mutapa state arose in the fifteenth century from the northward expansion of the Great Zimbabwe tradition. [... and existed until 1760, long after European contact]

Also, Mayan civilization shifted not collapsed

During the succeeding Postclassic period (from the 10th to the early 16th century), development in the northern centers persisted, characterized by an increasing diversity of external influences. The Maya cities of the northern lowlands in Yucatán continued to flourish for centuries more; some of the important sites in this era were Chichen Itza, Uxmal, Edzná, and Coba. After the decline of the ruling dynasties of Chichen and Uxmal, Mayapan ruled all of Yucatán until a revolt in 1450.

Mayan data point is more important, as Great Zimbabwe was not an independent civilization - it stayed it close contact with other civilized areas and had large levels of trade with them throughout its existence. Both datapoints suggest existential risks are much less likely.