cats

There are around 2.5 million ants for every human on earth.

If the ants collectively decided we should go, they could kill all of us in a day. The only places that would be safe are Antarctica (population varies between 4400 and 1100) and Greenland (population 56,643).

And don't expect some scientists at the south pole or Greenlanders to repopulate the world, the scientists couldn't and the Greenlanders wouldn't out of spite.