The atmosphere is thick and foul, and the rivers run an oily black.
The planet's squealing inhabitants are packed so tightly together, the barren ground beneath their feet is barely visible. They fight among themselves constantly, kicking and screaming, in desperate competition for space, air, everything. The weak, the sick and the old are trampled in this psychotic stampede. No-one cares. It's every beast for itself.
In orbiting spaceships, the aliens are amazed.
“I always thought Earthlings were an evolved species!”
“Sadly, that seems no longer so. There's no point in making contact now. All semblance of civilisation is lost.”