As you travel through the thick growth of a forest, a great shadow suddenly moves over you. You raise your head fast, but whatever it was, it was faster. However you try, you don't see anything, and nothing approaches you. Maybe it is better so.
Consider the idea of spontaneous genesis of life, as used to be belived. What strange kinds of life might arise from modern substances? What kind of vermin would a landfill produce, or an oil spill on the ocean?