Humans were around at the start of the ice age 100,000 years ago, but they weren't industrialised.
Glacial and interglacial cycles seem to be pretty consistent over the last half a million years. The causes are arguable, but have been linked to the Milankovitch cycle (relating to the Sun's movement about the solar system's centre of gravity), atmospheric conditions, and plate movements. There's no definitive proof of any causes. But it's entirely another thing to claim that current human activities are definitely not having an effect on climate.
