According to an article appearing in Saturday's (UK) Telegraph, we'd be nowehere today with air pollution:
Smoggy skies 'created life on Earth'
Hazy, smoggy skies on baby Earth could have provided the chemical building blocks of the very first life on our planet, according to a study of one of Saturn's moons.
Primordial Earth likely had a layer of atmospheric haze, similar to the one currently on the moon Titan, that may have served as the principal reservoir of life’s building blocks, according to the study in the Proceedings of the National Academy of Sciences.
The link is here. Have you thanked your local pollution today?