For North American they'd have to be before about 30,000 BCE.

But it's okay. I'm the little ray of sunshine here on Mudcat. I brighten EVERYONE'S day! Oh, it's so NICE to be nice! Aren't you SOOOOOOOOO glad to be alive? Remember, the clouds will roll away and the sun will shine brightly again! There is no night so dark that eventually the sunshine will not come! Why, even in the darkest night are the stars twinkling overhead! Everything and everyone is okay! Really! So pack up your troubles in your old kit bag and stroll down the sunny side of the street with me!