The team then considered whether different categories of essential life functions in the Archean Eon could have relied on iron or whether other transition metals were essential to life functions.

In the Archean, microbes that could not live with oxygen--anaerobic organisms--ended up with relatively small amounts of 13C.

Archean and Proterozoic History Reading: Chapter 8 This is a hard chapter to read. There's a lot of names and regional detail that we are not going to deal with. Try to filter out as much as you can ...

Earth's sea level has remained fairly constant during the last 541 million years, but a new study suggests the planet may have been covered by a vast global ocean 4 to 3.2 billion years ago.