xkcd: Earth Temperature Timeline

https://xkcd.com/1732/

For the last 40 million years, atmospheric CO2 has been in sharp decline.  Because of this, the climate for the last million years was very cold and dominated by mass glaciation.  Technically, we are still in the Pleistocene ice age which started 2.6 million years ago.

Due to changes in Earth's orbit, called Milankovich cycles, we get a brief warm period every 100,000 years, lasting just 10,000 to 15,000 years.  We are at the tail end of one of these warm periods. 

The Earth is halfway between its maximum tilt 12,000 years ago, which melts glaciers, and its minimum tilt which allows glaciers to grow.

All of civilization arose during this brief warm period.  The YouTube site, Kurzgesagt, refers to now as year 12,024 of the human era.