'garbage theory' of the origin of life
The 'garbage theory' is possibly the least appealing idea about how life began on Earth. Thomas Gold of Cornell University suggested1 that biological contaminants accidentally left behind by interstellar survey parties could introduce life to a previously sterile or prebiotic world. He envisaged a group of extraterrestrial visitors having a picnic somewhere on the young Earth. What if they dropped a few crumbs of food and from the microbes in those crumbs we eventually evolved?
1. Gold, T. "Cosmic Garbage," Air Force and Space Digest, 65 (May 1960).