42: The Question of Life

Hello, and welcome to Bedrock, a podcast on Earth's earliest history. I'm your host, Dylan Wilmeth. Episode 42, The Question of Life. I didn't plan for episode 42 to be about life. But it's a fitting number. For those who don't know, 42 is the answer to life, the universe, and everything. At least, that's according to The Hitchhiker's Guide to the Galaxy, the sci-fi comedy classic.

by Douglas Adams. If you're even vaguely acquainted with nerds, you've probably heard all that before. Maybe you even have a .42 stamped somewhere around your home. Here's what most people miss while laughing at the joke. In the book, 42 is the answer to life, the universe, and everything. But no one knows the actual question.

This puzzle is strikingly relevant to the actual search for life. In the rush to search for an answer like the oldest fossil or evidence for aliens, it's easy to forget the question. What exactly are we looking for in the first place? Fortunately, for every proposed discovery, there are hundreds of scientists scrutinizing the evidence, making sure the best questions are asked. Today, we examine another claim for the oldest fossils on Earth. This is not our first rodeo. In episode 16...

We saw ancient traces of carbon in the Jack Hill zircons of Western Australia, diamonds and graphite over 4 billion years old. The diamonds... turned out to be polishing grit, and the graphite remains ambiguous. In episode 33, we saw thin, rusty, straw-like structures in northern Quebec, around 3.8 billion years old. They might be iron-rich cells or chemical reactions with no influence from life. For now, there's no smoking gun. Everyone agrees...

Life was around during this time, but finding fossils remains difficult. You need a patch of seafloor or lake bed that's been untouched for nearly four billion years. The older you look, the fewer rocks there are, and they are very messed up. You take what you can get. This episode concludes a trilogy on the island of Achillea, off the coast of Greenland. In episode 40, we learn that Achillea is over 3.8 billion years old. On the Great Earth calendar, that's February 25th. In episode 41...

we learn that Achillea contains ancient iron-rich seafloors. All these points have been hotly debated over 30 years. Today, we'll examine the last and largest debate.

Do these rocks hold fossils? Part 1 Fertilizer The year is 1996. The Olympics are celebrating their 100-year anniversary. The Macarena is taking the world by storm. As the planet cheers and dances, we zoom in to sunny San Diego, California. The Scripps Institute of Oceanography has a beautiful campus. Looking out over green golf courses, hang gliders flying over seaside cliffs, and surfers on the beach. But today, we're inside a laboratory, with sunlight streaming in from the outside.

Sitting at a microscope is a spectacled grad student named Stephen Moisesch. If you're searching his name, it's M-O-J-Z-S-I-S. Moisesch. has been with us for two episodes and is a major player on the Greenland stage. But in 1996, his story is just starting. in front of moisish is the world's oldest slice of sea-floor a rusty stripy slab of rock three point eight billion years old named g nine one dash two six If your goal is to find Earth's oldest fossils, G91-26 is the best place to look.

Moises wasn't looking for fossil bones or leaves or footprints. Those bigger critters won't appear for a long time. He was looking for ancient bacteria. the fabled primordial ooze. To do so, he had to look through the microscope, and we're going to follow his journey, shrinking smaller and smaller down. The sample in question is a special type of rock, a banded iron formation. For more detail, check out last episode, or episode 32, but here are the relevant facts.

Sample G91-26 formed at the bottom of the sea as layers of red and gray iron settled on the seafloor, like sprinkles on a cake. Iron is not a fossil. but it's a good clue that life was around. Many types of bacteria love to munch on rust. Think of the iron layers like a watering hole on the African savanna, attracting critters who need to eat and drink.

Nemoeser scanned and scanned these rusty layers, looking for any signs of life. He didn't see any fossil bacteria, but he found something interesting. Every so often... He would spot a weird crystal, a small speck of pale blue in a sea of rusty red. These scattered blue crystals made up... less than 1% of the rock, but as Moises found more and more, he grew increasingly excited. What is this mineral, and why do we care?

This new crystal will be a character actor, a friend, appearing infrequently but dramatically in future seasons. You probably haven't heard of this mineral, but it does have a memorable name. Meat, appetite. You heard me, appetite. Now, when I say appetite, you probably think of being hungry. Working up an appetite. An appetite for destruction. This mineral's name is pronounced the same, but spelled differently. Our mineral is A-P-A-T-I-T-E.

As a gemstone, Appetite is usually blue or green, but can come in any color. Because of its diversity and beauty, It can be mistaken for more precious gems like topaz or aquamarine. That deceptive nature gives apatite its name. Apatite is ancient Greek for deceit. Or fraud. Not to be confused with Apathe, the banger pop song by Rose and Bruno Mars. Anyways, back to the minerals. Why was Moises so excited, so...

hungry for this appetite. It's not a fossil, but it is another strong clue that life was around. Appetite? is found in many locations, from lava flows to seafloors to the human body. In fact, appetite is the most abundant mineral in your body. But don't worry, it's supposed to be there. Appetite is the cornerstone of your skeleton. There are other materials mixed in, but the mineral appetite makes bones and teeth hard and strong. Without appetite, you would literally fall apart.

For example, bad things happen when your tooth enamel wears away. That enamel is made from appetite. So even if the word appetite is new to you, you've literally seen it. and carried it around every day of your life. Does this mean that the ancient Greenland appetites were once the bones of primeval creatures? Sadly, no. but they can tell us about life. The most important ingredient in appetite is the element phosphorus.

Phosphorus is an essential nutrient for life, even for creatures without bones. DNA, RNA, and cell walls all need phosphorus to be built. No phosphorus? No DNA. No life. This is why phosphorus is used as fertilizers on farms. It helps crops grow every year. Many of those fertilizers come from... Appetite minds. Geology and biology are closely linked. As we go forward, when I say appetite, I want you to think about fertilizer. It's not alive.

but it helps life grow. You can remember that life is hungry for appetite. When Moisesh found appetites in the ancient Greenland rocks, they were tiny. and scattered, smaller than grains of sand. Not enough to fertilize plants, but perhaps enough to fertilize bacteria. Remember, the appetite wasn't a fossil.

but it was a great place to look for them and finally as moisish zoomed even closer inside the appetite crystals He finally found what he was looking for. The strongest fingerprint for ancient life? Carbon. Part 2. Penciled In. The last time we talked about carbon was way back in Season 1, Episode 16. which kicked off a huge arc on the origins of life. Today's conversation is a spiritual sequel to that episode. I'm going to reference it a lot. Here's a quick recap.

All life on Earth, from bacteria to Bruce Springsteen, uses carbon as a fundamental building block. Inside you, the listener, 20% of your body is made of carbon. from your DNA to your fingernails. It's easy for the word carbon to become shorthand for life, but carbon by itself is not alive or a fossil. For example, a diamond on a wedding ring is pure carbon, but isn't a living thing. The Moises didn't find diamonds inside the Greenland Appetite,

but he did find another carbon mineral, graphite. Like diamonds, graphite is formed when carbon is pressure-cooked deep underground. Unlike diamonds, graphite is much more common and much easier to make. In fact, I'd bet good money that graphite is within 20 feet of you right now, inside a pencil. See if you can find one and look carefully at the tip. I'll give you a second. Every time you use a pencil, you're grinding down dark graphite minerals onto paper.

Sometimes, graphite is called pencil lead, but that's misleading. There's no lead inside your pencil. It's pure carbon. Graphite just happens to look like shiny, dark lead minerals, but there's no risk of poisoning if you chew on a pencil. There's enough lead around us without worrying about that. Speaking of pencils, let's get back to the point. Stephen Moises was looking for fossils inside Earth's oldest slice of seafloor.

He was so close and yet so far. The iron was a good clue, but not a fossil. The fertilizing appetite was a good clue, but still not a fossil. Now he found tiny scraps of graphite, pure carbon, the building blocks of life. Furthermore, that carbon was nestled inside the fertilizer, the perfect place for life to grow. But... By itself, carbon still wasn't enough. Fortunately, he had another trick up his sleeve. Carbon isotopes. Don't sweat if you're new.

or not chemically inclined, here's what you need to know about carbon isotopes. Again, this is summarized from episode 16. There are two main types of carbon atoms, light, And heavy. Here's the key thing to remember. Burn it into your brain as we keep searching for fossils. Life has light carbon. The carbon inside your body... or your pet, or your food, is much lighter than the average carbon of the universe. We'll describe why this is in a future episode, but here's a good analogy.

If I asked you to carry an apple or a watermelon, you'd probably choose the apple. Life is lazy and doesn't want to carry extra weight around. Anyone can find carbon inside a rock, like graphite or diamonds. That carbon could be a trace of life, or just plain old chemistry. But if that carbon is extremely light, That's a much stronger sign that it was once a living thing. When Stephen Moises looked inside the ancient Achilleus seafloor, that's exactly what he saw. The carbon.

had the same isotope signatures as bacteria full of light carbon atoms. Here's the model that Moisesch proposed. Once upon a time, Bacteria were living and dying on the seafloor 3.8 billion years ago. The bacteria were attracted to plentiful fields of iron and especially attracted to little seeds of fertilizer. Appetite crystals. The bacteria were filled with light carbon atoms, just like today.

As the sea floor was buried, the tiny cells became pressure cooked into shiny graphite crystals. Even though the cells were obliterated, the light carbon atoms remained behind inside. the dark graphite. In 1996, Moises published this research in the journal Nature, the highest place a geologist can go. Since then, Moises has been a researcher at UCLA in Los Angeles and is currently a professor at the University of Colorado in Boulder. We first met him way back in Season 1, Episode 15.

looking at the oldest evidence for Earth's oceans, a paper with nearly a thousand citations, huge for a geologist. But today's paper, the one discussing ancient fossils, is approaching... 2,000 citations, his most cited work. One reason for all these citations is 30 years of intense debate.

As you can imagine, such a large claim, one that could change the history of life on Earth, was met with intense scrutiny. It was time to test Moisesh's idea. were these graphite flecks actually fossils? Panic. For the past two episodes, we've met three different research teams battling over Achillia Island off the Greenland coast.

Each team has dozens of folks, but for simplicity, we've named them after their major players. Team Nutman from Australia, Team Moises from the USA, and Team Whitehouse from Sweden. Teams Nutman and Moises have been on the same side this entire season, agreeing on the age and the nature of Achillia Rocks. You might wonder why they're not one mega team.

why they don't just publish together. I don't know the full story, and I'm not going to turn this into speculative gossip. It's still a bit recent for that. There might not even be any gossip, it could just simply be an issue of timing. Here's my observation from the literature. Nutman and Moisesch and friends did publish... two papers together in the 1990s, one with each at the helm.

One is the huge nature paper I just described, Moisesh's great fossil discovery of 96, the light graphite from this episode. The next year, Nutman... described the banded iron formation itself. Less flashy, but very important. Since then, the two authors have not written any other papers together. The disagreement came three years later. Nutman and a team led by Yuji Sano in Hiroshima, Japan, published a short comment on the fossil paper.

We learned about such short comments last episode. If you feel a paper is very wrong, but don't have enough time to write your own paper, a comment is your place for a quick argument. These short comments are usually a bit punchier, written from a place of disagreement with a need to get a point across quickly and clearly. Whenever we talk about comments, feel free to get out the popcorn and soda.

These are the dramatic moments in academia. So why did Sano, nutmen, and crew disagree with Moisesh's fossils? Remember, Nutboom was on the original fossil paper with Moises in 96. What evidence changed his mind? Dates. On this show, nearly all our age dates come from the mineral zircon. It's the clock that sets the Earth calendar. The ticking of the clock comes as uranium atoms decay into lead.

Zircon crystals are great timepieces because they trap and hold uranium. Our new mineral friend, Appetite, the fertilizer, can also trap uranium. It's an alternate clock. One difference is that appetite is much wimpier than zircon. It can't take the heat as well. The wimpiness is a key part of Nutman's argument. Sano... And Team Nutman dated the Greenland appetites directly. The little seeds of fertilizer that cradled the precious carbon, the maybe fossils. Surprisingly, these dates were much...

much younger than other studies. September on the Earth calendar instead of February. For folks keeping score, that's 1.5 billion versus 3.8 billion years old. we won't see rocks that young until season seven. Does this mean that the entire rock is young and we should be throwing it out entirely? No. The Hiroshima crew argued that the rock was still February in age, still very old, but was squeezed and pressure cooked much later in September.

This metamorphosis had altered Moisesch's appetite crystals, had literally reset their internal clocks. Now, if the appetite was messed up, then maybe the carbon was as well. In other words, even though the rocks were old the carbon inside might be young.

with one crack revealed the floodgates of criticism were now opened and attacks came in from all sides we don't have time to cover every single debate but some papers went wild For example, two separate studies looked at the same Greenland rocks and couldn't find any graphite, no life-giving carbon at all.

For context, imagine visiting a desert and finding ancient human footprints, perhaps the oldest on earth. Now, someone else visits the same spot and says, sorry buddy, I didn't see any footprints here. Now that's some serious pushback. By the 2010s, the debate had calmed down a bit. Everyone now agreed... that the Greenland rocks did indeed have graphite inside, a little bit of ancient carbon. The question now was, was this graphite the original remains of ancient fossils?

or was it added later during metamorphosis for a kitchen analogy consider a cake full of sprinkles were the sprinkles baked inside the original cake Or were they sprinkled on top later? Let's examine three lines of evidence and reach our own conclusions, mostly from teams led by Dominic Papineau. and Ivo Lepland in London and Norway, respectively. Point 1. Isotopes. Carbon isotopes can be strong evidence for ancient life.

The lighter the carbon, the more likely it came from a living critter. This was the linchpin of Moisesch's fossil argument. The Greenland graphites had the same signatures as bacteria. But more recent studies have only found heavier carbon. It might have come from life. But it might have come from a non-living source like limestone or carbon dioxide. If you're looking for a bonafide fossil, you need evidence that can only be made by life.

two appetite the relationship between crystals of graphite and appetite is important according to moises the flecks of graphite were fossils of ancient life, while the apatite was the fertilizer that helped life grow. He described tiny, bacteria-sized graphite nestle inside larger appetite crystals, like sprinkles baked inside a cake. More recent studies do not see this pattern. Instead, they see dark graphite scattered

around the outside of these appetite crystals. In short, the sprinkles were put on the cake later, not baked inside from the beginning. other minerals until now i have described graphite and apatite hand in hand the fossils and the fertilizer that fed them in

Graphite was found hanging out with hotter mineral friends. Don't worry, I'm not unleashing any more names at you today. All we should know is this group of crystal bad boys... were the new kids in town, added during high-temperature metamorphosis billions of years after the rock formed. Other studies found graphites concentrated along cracks where hot groundwater had once seeped in. Altogether, these clues tell a story, one that doesn't involve fossils.

Once upon a time, about 3.8 billion years ago, there was an ancient seafloor. The seafloor was buried and cooked deep underground over billions of years. As the rocks were warped, groundwater infiltrated the cracks like a leaky basement, dumping many new crystals into the old stone, including carbon-rich graphite. That carbon might have come from life, but it probably wasn't the original inhabitants. This is the third time we've looked for fossils.

And the third time, we've drawn a bust. If you're bummed out, that's fair. I kind of am too. But there is a faint glimmer of hope. Some of the Greenland graphite is clearly not original. Everyone agrees about that now, even Stephen Moisish. But there is still a chance that somewhere... in a pristine pocket there could be original carbon from three point eight billion years ago the chances of finding it are now much trickier but not impossible

And if there's one thing that ancient geologists are good at, it's meeting those odds and beating them. So while there are no definitive fossils from Achillea Island, the chance of discovery... is still out there. Summary. For the past three episodes, we've focused on just one frigid little island. Achillea, off the Greenland shore. The aisle is a few city blocks wide, and the area of interest is the size of a large sports stadium.

The story of the island is more than just the rocks. It's about all the people who have studied and fought over them. We focused on three teams led by three men. Alan Nuttman. Steven Moises and Martin Whitehouse, but many, many others are involved. Their disputes might seem incredibly minute at times, but together... They have painted a more detailed version of the island's past. In 2025, here is the broad consensus. Achillea contains the oldest slice-of-earth seafloor.

were at least in the top three, over 3.8 billion years old. This seafloor was mostly dark and volcanic. But every so often, a pause in eruptions would let iron rain down from the ocean above. This iron was likely a feast for microbes, supplemented with tiny grains of fertilizer. like appetite. Life was almost certainly around, but if any fossils were preserved, they have been overprinted during burial and metamorphism. Who knows what future studies will reveal.

about Achillia Island. Here's the schedule for the next few sessions. On July 30th, I'll give an update on the great audience survey and plans for a Patreon coming in August. If you want to take the survey, there's a link in the description. There's also a donation button if you're feeling generous. On August 13th, we enter the last leg of our Great Greenland Adventure. and the final arc of Season 2. Join me at the foot of the Greenland Glaciers for Episode 43, Postcards from the Edge.

Thank you for listening to Bedrock. If you like what you've heard today, please take a second to donate using the link in the description. Every dollar helps make this show possible. And keep your eyes open for a Patreon coming soon. If that doesn't work, just tell a friend, rate the show, or leave a comment. It always makes my day, and that one person could be you. You can drop me a line at bedrock.mailbox at gmail.com. See you next time and rock on.