Archaeological records show us that humans apparently came to live here during the Altithermal
period, from 5,500 to 3,000 B.C., when the plains endured a period of very hot and dry weather.
Fossil bison and artifacts from an early altithermal
period arroyo trap in Wyoming.
Our conclusions could be regarded as counterintuitive by some, since many South American archaeologists believe that the "altithermal
" (the increase in temperature during the middle Holocene) is synonymous to "Climatic Optimum" (an increase in temperature and moisture).
This may refer to the severe Altithermal
drought of 7500-8000 B.P., which preceded the appearance of large-scale bison kills in the archaeological record (Reher & Frison, 1980, p.
Falling levels of shallow lakes in Michigan during prolonged dry periods (Altithermal
?) may have resulted in similar patterns.
The site is near Lake Huron and likely experienced a lowered ground water table until about 6,000 years ago at the end of the dry Altithermal period, when lake and ground water levels were lower throughout the Midwest.
Desiccation and fracturing were probably heightened in the Till Plains of Ohio during the dry Altithermal period (about 6,000 to 9,000 years ago) when prairies and grasslands of the Plains expanded eastward to central Ohio.
timberline advance in western United States.
archeology and paleoecology at Mustang Springs, on the Southern High Plains of Texas.
Apparently there was no warm-moist or dry Altithermal
interval in central Texas but rather a pronounced period of drier and possibly warmer conditions starting about 2000 years ago (Holloway et al., 1987).