From an article in the New York Times, August 31, 2016:
Geologists in Greenland have discovered evidence for ancient life in rocks that are 3.7 billion years old.
They are thought to be stromatolites, layers of sediment packed together by microbial communities living in shallow water. They are some 220 million years more ancient than the oldest previously known fossils, also stromatolites, from the Pilbara region of Western Australia.
The find, if confirmed, would make these fossils the oldest on Earth and may change scientific understanding of the origins of life.
Link: the full NYT article.