Binary Planets

Taking a break from scientific plausibility and/or horror, here's a little thought experiment I came up with:
What would life be like if Earth orbited itself around the sun?
In this instance, this particular planet evolved with a nearby neighbor, much life Earth. However, instead of direct collision, these two seem to have entered a stable orbit around each other. Sure, tidal forces have gotten fairly drastic at the poles, but this setup has an equatorial range perfect for harboring and diversifying life. While the solar year has a casual 400-day cycle, the two circle around each other in a matter of days. Life would grow, completely unaware that the looming object in the sky above holds their distant relatives...

Rendered in Photoshop