As scientists continue finding evidence for life in the ocean more than 3 billion years ago,those ancient fossils pose a paradox. Organisms, including the single-celled bacteria living in the ocean at that early date, and need a regular supply of phosphorus,but "it's very hard to account for this phosphorus unless it is eroding from the continents," says Aaron Satkoski, and a scientist in the geoscience department at the University of Wisconsin-Madison. "So that makes it really hard to define the fossils we see at this early era."
Source: phys.org