For a long time many people thought that life on Earth was less than 10,000 years old. With discoveries in the 19th century, that got pushed back to tens of millions. Then hundreds of millions. Then a billion or more years. Guess what:

Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures

Fossils of 4 centimeter stromatolites (mats of “biofilm,” or cyanobacterial scum) have been found in the Isua supracrustal belt in southwest Greenland dating to 3.7 billion years ago. This is 220 million years older then the previous record holder from Australia. This pushes the estimate of the beginning of single cell life back to more than 4 billion years ago, during the Hadean period. This is backed up by discoveries in late 2015 of traces of carbon in 4.1 billion year old zircon crystals that hint at a biological origin. Given that the Earth formed about 4.6 billion years ago, this is a remarkably short period for life to arise, and in one hell of an environment (Get it? See what I did there? “Hell” of an environment? “Hadean” period? Huh? Bah.)

Life, it seems, arises quickly in terrible places. Fossils may well exist on Mars, and possibly on Venus. Complex multicellular life, however, seems to take a bit more effort. Life on Earth peaked with bacteria for around three and a half billion years. The universe may be filled with planets coated in scum, with only a few advanced up to worms and bugs.