Oldest Amber Ever Found Rewrites What We Know About Plant Evolution

[00:00:00]Hello everyone, this is Anton, and today we're going to be discussing something somewhat unusual, but something that you probably have seen before. This. Amber.

[00:00:10]This beautiful golden substance that we often use in jewelry, or if you're a fan of science fiction, the source of dinosaur DNA in movies like the Jurassic Park. But it turns out that the reality of amber is a lot more interesting than what's usually described in fiction, and it actually tells us something really important when it comes to the evolution of plants. And as recent studies we're going to be discussing today uncovered some fragments of amber seem to be significantly older than we even thought was possible, pushing back the official record of these somewhat unusual features by at least 65 million years.

[00:00:49]And so today we're going to discuss exactly what amber is, why there is so much of it in various deposits everywhere, and of course why it evolved. Although I guess just to give you a bit of a spoiler, this is basically a type of plant defense. A way that the plant usually protects itself.

[00:01:05]And so let's talk about all of this in a little bit more detail, but let's start with the obvious question. So what is amber, and how exactly does it form? And also why does this piece of amber contain a tiny little frog from 100 million years ago? Well, based on what you might have seen in the Jurassic Park, and based on certain misconceptions, a lot of people think that it's basically tree sap. But tree sap that's millions of years old. And well, that's not entirely correct because in essence tree sap is mostly made out of water and sugars. So it's actually something that trees use to transport nutrients. It's kind of like their blood. In contrast, amber is this.

[00:01:46]It's fossilized resin. A much stickier and much thicker substance produced in specialized cells inside plants, usually when a tree is injured. In other words, it is either fence mechanism that usually only occurs when the plant itself is somehow damaged. And specifically, when for example, an insect starts boring into its bark or the branch ends up breaking, those specialized cells suddenly start to produce resin as a healing mechanism.

[00:02:16]And unlike watery sap, it's usually made out of something referred to as terpenes, designed specifically to heal wounds, block pests, and deter predators. Mostly because it usually also contains a very specific smell that some predators tend to avoid. And so, in that sense, it's actually not that different from what our bodies do when we get injured as well. And when the immune system starts to respond in certain ways. And though not all plants can produce resin, those that do produce it usually contain these [clears throat] resin canals that you see in this image represented by white dots. And so, here inside these canals, specialized cells secrete resin and can even be used to analyze the overall health of a tree.

[00:02:59]For example, trees with much larger and much more dense resin canals, or basically these structures you see right here, tend to be much healthier and produce much greater resistance to a lot of different stressors. But once again, not all plants produce this, and these types of canals are actually only common in various types of conifers, or basically trees very similar to pines, redwoods, and spruces. So, your typical trees containing needles. And while over millions and millions of years, these trees essentially evolved a kind of a biological bandage that helps them heal from various pathogens and various types of damage. But after millions of years of being buried somewhere in some kind of a sediment, and usually sediment that's oxygen-free, for example, inside clay or mud, this resin undergoes a process referred to as cross-linking, where molecules basically bind together and the substance itself hardens, eventually becoming almost like a rock, which is what we then refer to as amber.

[00:03:59]But, I guess the main question is, why did the plants evolve this ability, and why even start producing resin to begin with? Especially because this is actually a relatively complex and expensive defense system, and it seems to have evolved very early on. And the answer seems to come from several studies you can find in the description, with at least one study now discovering the oldest sample ever found. This is what you actually see right here, and it's approximately 385 million years old, which is nearly 200 million years older than the dinosaurs, and is at least 65 million years older than previous record holder. And while it this actually changes our understanding and the overall timelines quite dramatically, because here it actually tells us that even early trees seem to have already used this ability to protect themselves from something. And so, here researchers working in the Huajiresite Formation in China discovered hundreds of tiny amber fragments dating back to the Middle Devonian. But, none of them are actually large, or basically none of them are the ones that you've seen previously, where you can basically hold it in your fingers. Here, a lot of these fragments were super tiny, with the biggest one being approximately 1.5 mm across. In fact, it was so difficult to find and so difficult to see that researchers had to use UV light to try to find them inside the sample by making them fluoresce. And that's because amber fluoresces with this beautiful blue glow if you shine UV light on it. And though at first this may seem like a very trivial discovery, this is actually super important in helping us understand plant evolution.

[00:05:37]Because 385 million years ago, seed plants, or any kind of conifers, had not evolved yet. And we used to think that this type of our defense mechanism was more or less modern invention and mostly related to seed plants like conifers.

[00:05:52]With this discovery officially proving [clears throat] that much earlier non-seed vascular plants, so essentially plants that potentially resemble something like this, these somewhat primitive ancestors of angiosperms seem to be already capable of producing amber as a type of a complex defense mechanism. And well, the obvious question here is why? What exactly were they trying to protect themselves from and what was damaging the plants?

[00:06:17]Because once again, they only release resin when they're damaged by, for example, insects or when something breaks off a branch or damages the plant. Well, we know that during this time, during the middle Devonian, the world was going through a major transition. For example, plants were actually becoming much taller and were also developing wood and deeper roots and were finally forming some of the first forests on the planet. And though most of the fun stuff was mostly happening in the oceans, as this was basically the age of fishes, here even on the surface of the planet things were evolving extremely fast. But interestingly, at this time insects were not a problem yet. They had not become major plant eaters and instead something else was the main threat. Very likely wildfires and fungi. And as we've discussed in some of the previous videos, some which you can find in the description, at this point on the planet fungi were most likely the dominant species. And so the constant damage and attacks from parasitic fungi mixed with the high volcanic activity and the changing atmospheric gases eventually caused some of the early plants to start developing new types of defense. And so by evolving resin, these early plants very likely found a very easy way to seal up any wound and to heal any physical break. Something that was probably very dangerous to even earlier plants and something that fungi very likely abused all the time. And so in essence, this was a kind of a competition between plants and fungi, with plants eventually prevailing. And so this survival strategy eventually helped early vascular plants to dramatically expand across the continents, and to then physically change the structure of the planet as they started to transform the atmosphere, and of course the soil underneath. But while resin seems to have started relatively early, there was one specific time in history when it basically went into a kind of an overdrive, and seems to have been produced by a lot of plants everywhere, because there's actually an entire deposit in the ground where we usually find a lot of amber at the same time.

[00:08:25]And scientists call this period Cretaceous resinous interval, also known as C R E I. And this is a very strange period that lasted for approximately 54 million years. And in approximately 72 million years ago, with this period basically characterized by a massive global increase in resin production, and eventual production of huge amounts of amber in various types of sediment. And once again, here the question was, why?

[00:08:53]What happened during this period that possibly damaged the trees so much?

[00:08:58]Well, during this time, once again, the world was much warmer and much more humid. As a matter of fact, the atmospheric CO2 levels were at least twice as high as today, which naturally made plants a little bit happier because it allowed them to grow much faster, and eventually led to these massive conifer forests all over the surface. As a matter of fact, it was these forests that very likely dominated the entire planet. But at the same time, there was also way more oxygen in the air, up to approximately 30% compared to 21% that we currently have right now. And high oxygen means one thing, more fire. And so Cretaceous was very likely filled with intense wildfires that happened all over the place. And we know this very likely happened because charcoal, which is naturally produced when a tree burns, is almost always found in the same deposit as this Cretaceous amber. And so, the stress from multiple fires, combined with the attacks from various newly evolved herbivorous insects, very likely triggered trees to produce massive amounts of resin, resulting in so much of it that we've actually never seen anything like this during any time in Earth's history, which is why most of the world's famous amber deposits, like those in Myanmar, Spain, and Lebanon, come from this very specific window of time. And obviously, we do find amber here and there from other periods. Most of it, and here we're talking about the vast majority of amber, comes from this very specific period just over 80 million years ago. And a lot of it very often looks like this. Lots of different insects and lots of different creatures, including, once again, this poor little frog that also got stuck inside. And for scientists studying this, this is a really important time capsule because in most cases, resin, and specifically amber, is exceptionally good at preserving these samples with extreme detail, and most importantly, in three dimensions. Unlike a typical fossil that's usually just two-dimensional because it gets squashed by pressure, everything we found in amber so far is always 3D. traps things that normally run away, including soft-bodied insects, spiders, tiny frogs, but also flowers, feathers, and in some cases, even tiny lizards [clears throat] and pieces of dinosaur skin. And so, here, anything that's trapped inside is eventually stabilized, allowing us to see the internal anatomy and even evidence of past animal behavior, like, for example, pollination or parental care. So, definitely a really intriguing way to study the past without actually going there. With some recent studies even using chemical composition inside amber to track atmospheric changes for millions and millions of years by basically extracting the little bubbles from inside amber and by then analyzing the air. And this allows us to reconstruct the climate with surprising precision. But, this new discovery in China now basically sets a new precedent and a new benchmark for the history of life on land. And that's because here it shows us that this unusual biological technology evolved much, much earlier and was already used and relatively complex 385 million years ago. And so, this was not just an afterthought of plant evolution, but was a fundamental tool that allowed plants to conquer the land and allowed them to survive pretty much everything much, much longer than most other complex life on Earth.

[00:12:26]Eventually building the necessary ecosystem for everything else to evolve.

[00:12:30]And though there is a chance that we might find something even older at some point, right now 385 million years seems to be the record. But, on that note, once we discover something else about this fascinating plant defense mechanism, we'll come back and discuss this more in some of the future videos.

[00:12:45]Until then, thank you for watching.

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[00:14:05]>> Mhm.