Prehistoric people lived in southern Illinois for about 8,000 years, said biologist John Schwegman at the Cache River Wetlands Visitor Center in Belknap on Saturday.

Schwegman’s lecture was one of a series of monthly programs the center holds on topics about southern Illinois history, geology and local wildlife.

Schwegman, who said he’s had a lifelong passion for archaeology, said Paleo-Indians were the first known humans to inhabit the area 12,000 to 10,500 years ago. They were nomadic meat eaters who hunted woolly mammoths and mastodons

by following herds of the huge mammals as they migrated across North America, he said.

“You wondered how they could ever kill something that big with only a stone-tipped spear,” he said as he showed slides of spear points he found in local caves.

“It’s just kind of neat to be in a rock shelter and know that over 10,000 years ago, a hell of a hunter lived there,” he said.

Schwegman said it was difficult to find archaeological evidence of Paleo-Indians because they usually only camped in one area for a week or so.

He said the next geologic timespan, the Archaic period, occurred 10,000 to 3,000 years ago.

During the Early Archaic period, people ate mostly meat and used spears to hunt game.

At the beginning of the Middle Archaic period, about 8,000 years ago, people began to add other foods to their diets, Schwegman said. They gathered hickory nuts and acorns and consumed fish, shellfish and turtles.

Schwegman showed a slide of an area in Johnson County where Middle Archaic Indians processed the nuts they gathered. He said they used sharp flint tools to carve out a deep hole in the sandstone. They filled the hole with water and added crushed nuts. Then they placed hot rocks in the hole to cook the mixture. As the mixture cooked, the oil and nut meat would float to the surface, where it was skimmed off and stored in wooden bowls or leather pouches.

They also began to cultivate some native plants, which allowed them to settle in one place for a longer period of time, he said, although they still moved four to five times a year.

“About halfway through this period, they made a big technological advancement. They developed a crude axe — a tool for cutting down trees and working with wood,” Schwegman said.

Developments at the beginning of the Woodland period, which began about 3,000 years ago, led to cultural changes for the Native Americans living in southern Illinois, he said.

The Early Woodland Indians started making pottery and cooking in pots, Schwegman said. They raised gardens by sowing seeds from native plants such as marsh elder, goosefoot and squash, he said.

During the Middle Woodland period, about 2,200 to 1,500 years ago, trade among Native American groups increased. Archaeologists in southern Illinois found copper tools from the Middle Woodland period that likely originated in the Great Lakes area, Schwegman said.

He said during the Late Woodland period, southern Illinois Native Americans began to live near the tops of bluffs, which indicated they may have warred with the Mississippian Indians who were moving into the area.

“The final group of people who lived here were the Mississippian people, from about 1,100 years ago to about 400 years ago,” Schwegman said.

Schwegman said the Mississippian people were ruled by a chief who inherited his position. Mississippian culture, which was characterized by large earthen mound structures built by workers to house the elite, spread from the Midwest throughout much of the eastern United States.

He said Kincaid Mounds, which is located in Massac County, is the fifth-largest Mississippian site. The largest is Cahokia Mounds near Collinsville.

Mississippians developed a maize-based economy, which gave them a sustainable supply of food, he said.

“These people were the first true agriculturalists in southern Illinois,” Schwegman said.

They also quarried Mill Creek chert, a hard rock, from Alexander County and fashioned it into hoes, which they used for trade with other Native Americans, he said.

Schwegman said the Mississippian culture flourished for hundreds of years, but declined in the 1400s and vanished during the next couple of centuries.

The decline of the Mississippian culture has never been completely explained, he said.

“It might have been disease — yellow fever — that killed off a lot of them,” Schwegman said.

Schwegman said large earthquakes that originated from the New Madrid Seismic Zone struck the region during the middle of the 15th century and could have contributed to the decline of the Mississippian culture.

Ken Chilman, of Cobden, said he was impressed with the presentation.

“I thought it was excellent. He had good graphics and had done a lot of work over several years to prepare,” he said.

Shannon Harms, of Carterville, said she was very interested in the information Schwegman presented.

“This was the first time I had heard the hypothesis about the earthquakes,” she said.

The Cache River Wetlands Visitor Center will present a program on the critical role insects play in the pollination of farm crops, orchards, vegetables and flowers at 10:30 a.m. on March 17.