When Earth Turned Into A Giant Jungle

[00:00:00]When we think about prehistoric times, especially the age of dinosaurs and before, we usually imagine the earth as being hot and muggy. Whereas on the other hand, we often view the sun asoic or age of mammals as being the opposite in the sense that we consider it colder and more dreary. And this perception has largely been created by the ice age, which brought worldwide temperatures down to their lowest points in hundreds of millions of years potentially. And even when looking at the Cenazoic in general, it does tend to have been colder than previous eras. However, what is also true is that it is just a myth to believe that the whole thing has been one giant cold spell when in reality there have been hot periods sprinkled throughout. And ironically, one of these periods ended up being one of the hottest moments in Earth's history and an event that turned the world into essentially an oversized microwaved jungle which shared some resemblance to the bizarre carbonifpherous period which transpired 300 million years before. And this was the Paleocene Eocene thermal maximum or PETM for short. Now, historically, the dinosaur ending asteroid has often been depicted as having ushered in a nuclear-like winter and permanent colder temperatures. And while did certainly dampen the temps for a bit, the world did ultimately return to a pretty warm climate just as the Cretaceous had been, with the first stage preceding the Mesazoic, having been a relatively warm time for Earth.

[00:01:13]In fact, even at that time, there was no permanent polar ice caps on the planet, while carbon dioxide levels were far higher than today. And this heat remained relatively stable for some time and indirectly eventually led to extensive tropical and subtropical forests developing worldwide with mangrove, cloud, rain, and swamp forest all becoming fairly abundant. Though that said, most of the trees you'd see in these ancient forests were the same as each other. In other words, not much diversity, being dominated by just a few species. Meanwhile, animals on the other hand were still recovering from the extinction and were in general fairly small. But they were getting bigger, especially as the Paleocene, the epoch which the Danian fell under was coming to a close. And by then you did see animals that could be half toned in weight. So size was increasing fast.

[00:01:56]However, this recovery and somewhat relatively stable climate was about to be thrown straight into the depths of chaos. As about 55.8 million years ago, the temperature was suddenly cranked to 100. And I don't mean that things started to slowly get warmer. No, no, no. It was more like one day warm and the next day you're in an oven. And we see this reflected by graphs that have examined past temperatures. There's a lot of smooth uphill and then suddenly this giant ugly spike that sticks out like a sore thumb, literally. Now, this is not something we've never seen before. Such rapid global warming events are referred to as hyperothermals. But this one is by far the most intense of the entire cenazoic age with temperatures rising up to 8° C or 14° F worldwide. which just for comparison with all of humanity's activities, the world has only increased by about 1.4° C since the industrial revolution. And that has already had a massive impact.

[00:02:49]And also, just to reiterate, the world was already hot with the average being up to 28.3° C or 82.9° F. So about 40% hotter than currently. And again, this was before the Paleocene Eocene thermal maximum. And so during it, it's thought that the average might have skyrocketed up to a blistering 34.5 degrees C or 94.1 degrees Fahrenheit, which for perspective is hotter than even the current hottest country on Earth. And it's believed that even the high latitude seas of the Arctic were as warm as subtropical waters now. Meaning that if you went to Antarctica, you better have brought some swim trunks and sunscreen. And so this all begs the question of why? Well, we know this unusual event has something to do with an astronomical increase in carbon dioxide as the ppm or parts per million went up from about 1,000 to over 2,000, which is more than four times the present levels. And such a massive rise in carbon dioxide isn't just a normal part of the carbon cycle. It clearly indicates that something transpired, something which happened to inject a massive amount of carbon dioxide straight into the atmosphere. Now, we do not know exactly what the culprit behind this event was, but there are a lot of contenders. Volcanic eruptions, massive underground pete fires, changes in the ocean circulation, and even comet impacts have also been cited and more. I mean, even terrestrial animals themselves have been blamed by some who believe that an increase in respiration efficiency led to an increased output of carbon dioxide since that is exhaled when an animal breathes out. And this therefore might have pushed carbon dioxide levels even higher. But again, for now, any agreement on what really happened remains elusive. What is very clear though and very agreed upon is that this heatwave had major impacts on the entire planet and seems to have lasted for about 200,000 years or about 28 times longer than the last glacial maximum lasted during the ice age. And if the latter, i.e. the peak of the ice age caused so many changes in just 7,000 years. Imagine how impactful all this heat was. And so unsurprisingly, virtually every aspect of the planet underwent dramatic shifts. And one thing that also had its own impacts was that the climate not only got hotter but also much wetter as well with evaporation rates increasing especially in the tropics and rainfall getting way amped up. This supercharged the already abundant forests leading to tropical and subtropical forests expanding even further and increasing their range leading to them growing in places that we don't usually associate warm tropical forests with. For example, Texas, obviously much drier area, was at the time covered in tropical rainforest and seasonal tropical vegetation. While in the Arctics, palm trees were plenty and even a zola ferns could be found. Two flora which today are completely void from these areas. And so basically this growth in subtropical and tropical vegetation basically turned the planet into one giant jungle and swamp. As swamps too became far more prominent at this time, especially as sea levels rose and flooding occurred. This totally transformed the face of the planet and turned it into an environment reminiscent of the extensive forests and swamps Earth experienced during the mid Cretaceous and even the very far back Carboniferous which happened so long ago. And just like those two previous times, the changes of environments didn't just make things look different, it also forever altered the timeline of evolution and is actually very relevant to our own story. You may have thought that it was the dinosaur's demise that led to the mammals you see today, including us. And while it did open up the door for mamalian rule, it was really the PETM that had a far more direct involvement in the specifics as it led to a large increase in mamalian abundance which included the emergence of many important mammal clades that are a massive part of the biosphere today.

[00:06:22]Among them were the artactula or even toad unullet which includes things like giraffes, bison and even whales. Then there was the parasidactyla or the odd toad unullet who were composed of horses, rhinos, tapers and the extinct hydodonte. And then finally, the world even saw the arise of the first true proto primates such as the purgator.

[00:06:42]What's odd is that this explosion in diversity is thought to have stemmed from something that may come as a surprise, and that's dwarfism. You see, virtually all mammals are warm-blooded, meaning that we can regulate our own internal temperatures, which is good, but it can also make us more prone to overheating. And therefore, when it got as hot as it did during the Paleocene Eocene thermal maximum, mammals started to shrink in order to stay cool. And this dwarfing effect might have led to more speciation with the larger mammals like ecquids, mesanicids, and the oxyanids being especially affected. On the flip side though, already very small mammals such as the arinosids were left pretty much untouched. Then there were also animals that experienced somewhat of the exact opposite effect. And this was of course our cold-blooded friends, the reptiles. As since they rely externally for heat, the increased warm supplied them with more spare energy.

[00:07:30]Therefore, with the concern of staying warm no longer being as much of an issue, many reptiles grew in size and became highly diversified. with some formations from this period harboring over a 100 species of reptiles. Based on fossil records, it seems that worldwide turtles became very large and many snakes balloon in size as well, especially those that were aquatic, leading to literally the largest sea snakes of all time, such as the Paleopilus, a potentially 40 ft or 12.3 m long monster that lived in the marine waters surrounding Europe, North America, and North Africa.

[00:08:01]Crocodilamorphs also got a helping hand from this event with multiple groups of predatorial land crocs becoming quite successful such as the sebids and mechas both of which would produce more than a handful of effective killing machines that frankly make Komodo dragons seem rather tame. And so this arise of large and abundant reptiles as well as a speciation of dwarf mammals led to a pretty interesting world where in many environments especially in the western hemisphere you'd find an extensive amount of aonian families but then they would still have a few reptiles being at the top of the food chain despite the cenazoa commonly being nicknamed the age of mammals. And one of the best examples of this is the Wasatch Formation. A massive sprawling area that covers numerous states in the United States and is well known for being highly phosiferous, giving us a clear look into what life was like during this hot pot era. And one thing we see is that the forests were not just dense and plentiful, but they had also become diverse as well as large amounts of magnolia, birches, redwoods, nettles, laurels, and more were present. And within these ancient rich forests, the earth was teameming with all walks of life. And this included our very own kind. Not mammals. Well, yes, mammals, but specifically primates, who were still quite primitive and didn't look like how you might typically imagine primates to be, as things like apes and monkeys were still distant twinkle in evolution's eye. Instead, most primates here were members of the extinct plesioapform group. In general, these guys tended to be very small and grassile while sporting longer tails and skulls, giving them an appearance most comparable to that of lemurs. There are also those that looked arguably more like squirrels than anything else. Well, I guess more like if a squirrel had a baby with a monkey. And thus far, dozens of primates have been unearthed from this time, showing that they were thriving and benefiting off of the abundance of trees. And the dense coverage the forest provided also supercharged other small groups like the Lepta, Lipotya, macroke, multi-tubercculada, folioda, and the glires which consist of rodents and lagamorphs. Many of these groups did appear archaic and ancient, but they were still very clearly mamlon in overall looks. And we do see this pattern in the slightly, and I do mean slightly, larger mammals like the early ariodactyls, who are dwarfs compared to those that live today. Many of them, in fact, you could likely pick up with just one arm. And they were at this time a pretty adorable bunch as some that we know of like the Dicodexis and Daikobuniday are often compared to still extend dwarf ariodactyls such as the chevotain and dwiker who almost seem to have been designed for peak cuteness. I mean just look at them absolutely adorable. Alongside this group you would have also found the first parasided who were actually more abundant and again slightly larger as many reach the size of medium to ferized dogs. So not giant by any means, but still a step in the right direction. At this time, most of them tended to look a bit like what you may imagine a primitive horse to look like, regardless of group, as the rhinoertoids, ecuids, brontoers, and tapioids all had a bit of the same build in a superficial sense with them being compact, four-legged, and without the visible structures that we often use to distinguish them visually. And what I mean by this is that the rhinoseratidia hadn't yet devolved the horns. The tapioids were snoutless, and the brontoers lacked their built-in rams.

[00:11:10]And compared to their modern or later selves, I'd argue that horses look the most unchanged with the biggest visual difference at this point being basically their many sizes. And though each group would eventually balloon in size, their small stature at this time did wonders for them through the petm as it not only helped keep them cool, but it also allowed them to use a thick brush as cover. Now, with all this said, while there were no true giant mammals, say comparable to elephants, there were those that were far larger than these lot, namely the pandadont and fakacodonte. two extinct group herbs that were essentially the first mammals to become relatively large in the absence of dinosaurs with general like the berry lambda even managing to reach the size as a pony weighing about 650 kilos which basically made it the Godzilla of its time albeit a herbivorous one and this relatively giant size would have protected it from almost all the predators within its environment and trust me when I say there were a lot of predators with about five different groups being the shot collars so you could say first You had the Masaay, a family of small weasel and fairel like carnivores that were in some cases aroreal and often fed upon tiny prey like bugs, birds and small mammals.

[00:12:18]Then there was the oxyaniday meaning the sharp hyenas who remembers the fairy order and despite what their name may have you believe were not hyenas and did not really resemble them either actually being more similar in appearance to otter and badgers that walked on flat feet and tended to be larger than the masids with some of the species being about the same size as a large fox. With that being said, they wouldn't get much bigger in the distant future. And the same situation was also seen in another group that would one day become one of the Earth's most dominant predators, the hyenodons. Now, again, despite the hyena portion of their name, these guys were not really hyenas, only being named hyenodons due to their similarly shared teeth. Though, with that said, while the two groups did share some dental features, the teeth of the hyenodons were actually better designed for sharing flesh instead of crushing bones as some hyena teeth are. And given that they were wolf-sized at the time, they had quite a few options for flesh to choose from. Some evidence also suggests that this group was relatively cursorial for the time, meaning they were efficient runners. And that might not sound so special nowadays, but back then it was pretty revolutionary as many mammals were quite slow compared to their modern-day counterparts. Moving down the list, our third shot collars were the vivor. And once again falling in line with confusing names, this extinct group were not the vivers earth still has. So again, you may ask why the name? Well, essentially it was once thought that this ancient group were the ancestors of the Varids given the almost identical looks and presumably had similar lifestyles. Yet we now know that they actually were not related, but the name has stuck. And unsurprisingly, said name means the ancestors of the Varids.

[00:13:53]And like I said, there were some that were indeed the Varidlike, but there were also others that broke the blend with a few being more like to Monguses than the former. And ultimately, this was a very diverse group who were extremely successful predators during this time. But with that said, as far as time traveling humans go, they were not the worst group to run into. That title instead likely went to the wolflike measanids, who somehow against all odds had resisted the heat and had become remarkably big with the Pakyena, for example, sometimes weighing up to 396 kilos or 873 lb, an absolute anomaly amongst the landscape. and who was no doubt a lethal apex predator who utilized massive robust teeth to demolish various animals. And based off of wear patterns, it's also thought that bone made up a large part of its diet, thus increasing its versatility. And then finally, last but not least, the Arcticids, who are like the Mesaids, fairly large for the time, as well. Some were just the size of a cat, domestic cat that is. Others like the Arctic scan mumach are believed to have rivaled small bears in size, making them again amongst the largest predators alive at the time. Albeit truthfully calling them shock collars is relatively generous as they were not doing so well in the heat.

[00:15:06]And actually, it may have been directly or at least indirectly the cause of their demise as they had first evolved during late Cretaceous, but were now finding themselves in a catastrophic decline that did lead to their extinction before the PETM had even ended. But as you can see, even with the imminent doom of the Arcticids, there were still plenty of Aleon carnivores to choose from along with of course the plenty of herbivores that we just talked about. But remember, these were in many ways not the true rulers, as that of course would again be the reptiles who had rode the heatwave all the way to glory. And this list included some of the Earth's first bow constrictors, a multitude of turtles, both hard and soft shelled, plus a few with extremely long tails, iguanas, worm lizards, anguay, potential beaded lizards, and a trove of other unidentified lizards and snakes.

[00:15:52]And like I mentioned, there is also plethora of crocodilians thriving as well. many looking superficially similar to modern ones. But because of increased diversification amongst them, you did have a lot of these species specializing in niches that you might not usually associate with crocs. For instance, one species had turned it into a shelled animals worst nightmare. Whereas fish, on the other hand, probably had no qualms with it. That said, there were of course crocs that were pretty standard too, being of the larger stature side and sporting opportunistic lifestyles where anything that fit in their mouth was good enough for them. But there's one caveat that is very important to remember, which is do not think that staying away from the water would keep you out of a croc's reach. As during the Paleocene Eocene thermal maximum, the dangers were not just limited to fresh water. As one group walking around were the hoofed crocodiles. And yes, you heard that correctly, hoofed. Although truthfully, this group scientifically known as the Plano Cranaday didn't actually have any hooves. Rather, they were equipped with blunt clawed feet that simply resembled hooves. Yet regardless, this was still a very clear sign that these guys were highly adapted to life on land and uh running. Also sporting long, athletic legs. Of course though, in typical Croc fashion, they also kept what makes Crocs well scary.

[00:17:04]In other words, extensive body armor and jaws that would uh take a nice chunk out of you, making them among the last animals you'd want to encounter. And though not in the Wasatch formation, you cannot forget that in this time if you were traveling the globe, you could have also came into contact with the sebids and mechukun, two additional groups of crocodilomorphs that also had of course wicked teeth and in many cases were even larger than the hoofed crocodiles. Oh, and uh these were land crocs, too. So clearly the lands of Earth were teameing with all sorts of life at this time and I guess you could say has it ultimately benefited mammals. Yet with that said, the situation in the water was a bit different. It seems that the excessive heat had made things a bit more uncomfortable underwater than above as the PETM was a bit of an aquatic extinction event in reality. So much so in fact that certain groups like benthic for manifera experienced Dios that was more severe than what they experienced during the KT extinction event. You know when that giant asteroid slammed into Earth and it seems that shallow marine ecosystems in particular were devastated by this event with many of them having simply collapsed under the heat.

[00:18:07]Although it wasn't necessarily the heat itself that was the killer, rather other changes that occurred as a result of this event. And one major change that took place was enoxia wherein oxygen is depleted from the waters. You see, elevated seawater temps, water stratification, and oxidized methane released from undersea structures all led to this depletion in oxygen that seems to have affected most oceans and seas, especially the North Atlantic, turning all of them into death traps for many. Then on top of that, the PETM also seemed to have radically changed the planet's circulation patterns, essentially reversing currents worldwide and transporting warm water to the deeper parts of the ocean, which didn't help either. And uh the problems would only continue as the ocean started to experience acidification as well with the pH dropping about 0.46 46 units, which is no bueno as it reduces the availability of carbonate ions, which are essential building blocks that marine organisms need to build and maintain their shells and skeletons. And so with all these factors combined, there are some major hurting in many marine environments and even freshwater ones, too. Yet, I will caution you that those with lassophobia would still need to be wary as numerous dangers lived beneath the waves. Sharks in particular were thriving despite the challenges having filled in the gaps left behind by the KT extinction event. While the warmer waters resulted in their ranges becoming far greater, meaning that even in places like Scandinavia, the UK, or the poles for that matter, sharks of many kinds were commonplace. A lot of them were also the same kind of sharks you still see today. In other words, goblin sharks, recquum sharks, sand sharks, bullheads, cow sharks, etc. And of these species, a lot of them were surprisingly similar to the extinct ones as well. But then there were also a few species that um let's just say we should be glad remain in the past. And some prime examples of this are seen in the mackerel sharks specifically credina pendicolada and the odus oblique. Two very large predators with the former being comparable to a great white. Well, then the Odus oblique was able to reach 9 m or 30 feet in length, making it not only the largest predator on Earth at this time, but likely the largest animal period during the entire PETM. And just as a cherry on top, you also had giant ghost sharks along with various predatorial fish like early barracudas.

[00:20:24]And then of course, you can't forget about those giant aquatic snakes I mentioned earlier who were definitely lurking around these waters as well. In addition to these guys, fully marine crocodiles were a reality, too. Namely being the Dyrus who ruled the waters as far as crocs go. Now, this group was defined by having very long and thin and garlike snouts that took up large parts of their bodies. Yet, don't get it twisted because fish weren't the only thing on the menu regardless of what their skull shapes may have you believe.

[00:20:49]As across the board, they held various niches and also sported different dentitions, suggesting that each was specialized in something a little bit different. And like the sharks, they too had been around during the Cretaceous, but in the absence of the Mesazoics, aquatic threats in the presence of warmer waters had made quite the name for themselves and held quite the global range. Thankfully, they didn't all tend to be superersized, but some of the species did hover around 20 ft or 6 m in length. So, swimming into one of them would definitely not have been very fun or good for life. And on top of aquatic marine environments, this family is pretty much found in every other kind of water, too, both brackish and freshwater. Meaning that on top of the blistering heat, crazy mammals, and numerous reptilians, you pretty much had to watch out for giant crocs no matter where you were, including the possibility of them running you down on land. And uh did I mention there were bugs, too? Because there were lots and lots of them, as the heat was very helpful for them, too, leading to massively expanded ranges into a bloom and diversification and a surge in insect repellent prices. So with all this said, it doesn't need to be well said that of all the times you could choose to visit the Cenazoic, the Paleocene Eocene thermal maximum would definitely be one of the more questionable and uncomfortable times to choose. But the good news is that this whole strange event wasn't that long, at least in a geological sense, seeing that as mentioned, it only lasted for about 200,000 years. In other words, shorter than the time that even we have been around and we're pretty fresh. Now this leads to the logical question of why did it end? And the answer to that is it's believed that a mixture of silicate rock weathering which traps carbon and stable molecules and the organic burial of carbon through essentially dead things getting stuck in sediment is what brought the carbon dioxide levels down to a bit more reasonable levels. But overall the climate would remain pretty toasty even after this. And actually it would not be the last time real heat reared its head either. As for ass seemingly similar reasons, another event like the PETM would happen not so long after that has now been dubbed very creatively the Eosene thermal maximum 2 where in temperature spiked once again.

[00:22:51]And ultimately both of these hyperothermal events are part of the broader early eosene climatic optimum. A sustained interval of a few million years that is one of the hottest periods of sustained heat the earth has ever experienced. But still of all the heat that generated it was the PETM that turned the dial to the highest. And since then, nothing has been able to top it. Probably for the better.