That is a really CRAPPY climate up there...kudos to those guys for surviving - 5000 years ago.
At the same time Lake Erie was substantially larger than it is now and reached over into Western Indiana. It drained off 4,000 years ago (as the Niagara River dug into the Niagara Escarpment).
The Sahara was settling into desert conditions, as was Arabia, and Egypt was rising along the banks of the Nile. Still, the Great Western Depression was also a lake ~ it dried up after Roman times.
It was warmer 8000 years ago than it is today.