Are Mammals Middle Aged?

 Earth could become uninhabitable to mammals, specifically, in about...250 million years. That's about the same amount of time they've been around.

Why?

The cycle of continent formation will bring the continents back together into an equatorial supercontinent, nicknamed Pangea Ultima.

This will result in extremely hot temperatures in the center of the supercontinent. Mammals might survive along the coast.

Then there will be 2.5% more energy from the sun. We're talking average monthly temperatures of 140 degrees Fahrenheit here.

Reptiles or dinosaurs/birds might become more dominant again, but small mammals might survive until the continents split again...and then re-evolve. Maybe.

But there's one group of mammals that might not have problems.

Cetaceans might survive, even thrive. Their return to the water is generally believed to be permanent, but who knows?

As for humanity? If we're still around then, then we might have to move into the water ourselves.