But why did this region look so different back then? The ice sheets to the north, although retreating 13,000 years ago, still dominated the climate here. It was much milder and wetter than today, ideal conditions for woodland to flourish. 

 

This is how much of the northern plains must have looked when the first people arrived. Not open prairies as it is now, but a parkland of trees and grassy meadows. 

 

This is a relic of those times. The Osage orange. Every autumn it produces these enormous fruits, huge numbers of them, more the size of great fruits than mere oranges. 

 

But there’s no animal alive today that's big enough to pick and eat them, so this bump of crop just rots. The Osage orange glory days are long gone. But its harvest was once an annual feast for many ice age animals, including mammoths. Fruit must have been a real treat for these grass eaters.