The oldest evidence for microbial life has been found in Greenland, with fossilized 3.7 billion year old stromatolites (layered bacterial colonies) found in the rocks. Here's what they look like:

And here's the abstract of the paper:

Biological activity is a major factor in Earth’s chemical cycles, including facilitating CO 2 sequestration and providing climate feedbacks. Thus a key question in Earth’s evolution is when did life arise and impact hydrosphere–atmosphere–lithosphere chemical cycles? Until now, evidence for the oldest life on Earth focused on debated stable isotopic signatures of 3,800–3,700 million year (Myr)-old metamorphosed sedimentary rocks and minerals from the Isua supracrustal belt (ISB), southwest Greenland. Here we report evidence for ancient life from a newly exposed outcrop of 3,700-Myr-old metacarbonate rocks in the ISB that contain 1–4-cm-high stromatolites—macroscopically layered structures produced by microbial communities. The ISB stromatolites grew in a shallow marine environment, as indicated by seawater-like rare-earth element plus yttrium trace element signatures of the metacarbonates, and by interlayered detrital sedimentary rocks with cross-lamination and storm-wave generated breccias. The ISB stromatolites predate by 220 Myr the previous most convincing and generally accepted multidisciplinary evidence for oldest life remains in the 3,480-Myr-old Dresser Formation of the Pilbara Craton, Australia. The presence of the ISB stromatolites demonstrates the establishment of shallow marine carbonate production with biotic CO 2 sequestration by 3,700 million years ago (Ma), near the start of Earth’s sedimentary record. A sophistication of life by 3,700 Ma is in accord with genetic molecular clock studies placing life’s origin in the Hadean eon (>4,000 Ma).

I've emphasized the last sentence for a reason. We've known for a long time that life arose early in Earth's history. Geochemistry and the genetic clock have told us that life arose about 4 billion years ago, very shortly after it cooled from a molten state. What these fossils are are the first visible physical evidence of the existence of cellular life. They confirm what we already know. There's nothing in the existing body of evolutionary evidence to suggest that we can't find even older cellular fossils.

But, you know that won't stop creationists from claiming that this discovery is a problem for science.

Reasons to Believe is an old Earth creationist organization -- they have no problem with the idea that the earth is 4.5 billion years old. However, they do insist that life arose by magic, poofed into existence by their supernatural deity, so they desperately want to argue against the evidence of a natural origin. Fuz Rana wrote about this discovery, saying Science News Flash: 3.7 Billion-Year-Old Fossils Perplex Origin-of-Life Researchers .

I read the paper. Nowhere in it is anyone "perplexed" or even "surprised". Quite the opposite: the authors point out how this fits just fine with existing models of the history of life. Rana has to really work hard to twist the story.

The researchers who recovered and analyzed the Isua stromatolites expressed similar surprise: “The complexity and setting of the Isua stromatolites points to sophistication in life systems at 3,700 million years ago, similar to that displayed by 3,480–3,400 million-year-old Pilbara stromatolites.” From a naturalistic perspective, the only way for these researchers to make sense of this discovery is to conclude that life must have originated prior to 4 billion years ago. They state: “This implies that by ~3,700 million years ago life already had a considerable prehistory, and supports model organism chronology that life arose during the Hadean (>4,000 million years ago).”

Oh, wait. Where do you see surprise in any of those quotes? That makes even less sense when you go back to the paper and look at that quote in context.

The recognition of ~3,700-Myr-old biogenic stromatolites within Isua dolomites indicates that near the start of the preserved sedimentary record, atmospheric CO 2 was being sequestered by biological activity. The complexity and setting of the Isua stromatolites points to sophistication in life systems at 3,700 Ma, similar to that displayed by 3,480–3,400-Myr-old Pilbara stromatolites. This implies that by ~ 3,700 Ma life already had a considerable prehistory, and supports model organism chronology that life arose during the Hadean (> 4,000 Ma).

Rana left that bit off.

RtB really doesn't like the actual way that origins of life researchers think nowadays. LIFE IS CHEMISTRY. The origin of life was almost certainly not a chance event, but a product of geochemical processes that would have begun as soon as conditions were locally suitable. No one considers it surprising anymore that the chemical reactions that preceded life (and the boundary between "chemical reactions" and "life" is extremely fuzzy) would have emerged as soon as opportunity arose. The directions that life would have taken after complex biochemistry started building up would have been shaped by chance, but otherwise, no, we expect that abiogenesis, or at least the conditions that would lead to abiogenesis, was a product of necessity rather than chance.

So this is a paper that repeatedly states the good fit between the discovery it describes and existing theory, and RtB repeatedly insists that the paper says the exact opposite. This is not honest.

Here's something else that is dishonest: Rana claims this discovery supports the Bible's model of the origin of life. Disconnect your bullshit meter before reading the next quote, because otherwise it's going to go sproing and send shrapnel flying all over the room.

While the discovery of 3.7 billion-year-old stromatolites confounds evolutionary explanations for life’s origins, it affirms RTB’s origin-of-life model. This model is derived from the biblical creation accounts and make two key and germane predictions: (1) life should appear on Earth soon after the planet’s formation; and (2) first life should possess intrinsic complexity. And both of these predictions are satisfied by this latest advance.

His point (1) does not distinguish his creationist model from an evolutionary model, since biology and chemistry say exactly the same thing. However, it's false because the Bible says nothing specific about the origin of cellular life. The authors of the Bible didn't even know about cells, or genes, or molecules, or hydrogen, or reduction/oxidation reactions, or any of the stuff that is the foundation of the models Rana is so blithely appropriating. His holy book is a sucking black hole of ignorant rationalizations, not a source of theory or evidence.

His point (2) is also false. This discovery says nothing about the "first life" or whether that first life had "intrinsic complexity" (whatever the hell that is). These are 3.7 billion year old fossils. The authors point out that models of life's origin suggest that "first life" would have appeared approximately 4 billion years ago.

Do the math. 4 billion - 3.7 billion = 300 million years.

Maybe someone needs to inform the crew at RtB that 300 million years is a very, very long time.

They can keep poring over their sacred book, but I'm pretty sure there is nothing anywhere in the Bible that's going to help them understand geo- and bio-chemistry going on over long periods of geological time.

It's also not going to help them understand evolution. Stromatolites aren't in the holy book, either, nor is the fact that it was going to take a few billion years of evolution to get from single-celled bacteria to arrogant, delusional multicellular apes who think grandpa's goofy stories are immutable truth.

Nutman AP, Bennett VC, Friend CR, Van Kranendonk MJ, Chivas AR (2016) Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures. Nature doi: 10.1038/nature19355.