That day is today.

One quote pops into mind --

"Mutation: it is the key to our evolution. It has enabled us to evolve from a
single-celled organism into the dominant species on the planet. This process is
slow, and normally taking thousands and thousands of years. But every few
hundred millennia, evolution leaps forward."-Professor X.

-- when I find out about this:

Today is the day man loses his place as the apex predator at the top of the food chain.

Today is the day that may lead to our extinction.

Today is the day the tables are turned.

Today is the day the cows became carnivorous.