If all of Earth's history were squeezed into one 12-hour period, how long ago did Precambrian time end? How long did the Cenozoic Era begin?

That it

Explanation:

There have been mass extinctions during the Cenozoic as there were during the Mesozoic and Paleozoic, but not as many animals and plants have disappeared. Finally, humanity appeared during the last two million years. The human lineage only diverged from our most recent common ancestor about 5 million years ago; less than half of 1% of that time, and modern Homo sapiens is only between 200,000 and 50,000 years old, depending on your definition.