 Well, here's our first video lecture, guys. You're gonna have to give me some feedback and let me know if there are any technical or logistical issues that I need to address for the upcoming ones. If I'm talking too fast, too slow, you want a little picture of me in the corner with my head talking, means I'm gonna have to dress up and clean my house, but I will do that for you out of my commitment to the class. But seriously though, let me know what, if anything needs to be changed in terms of this format so we can make it an effective learning environment for everybody. So today's talk is gonna be mostly about the Ediacary and the Cambrian periods, but I wanna take you through a quick reminder of where we left off last class. So if you remember last class, we were talking about the transition from the boring billion, the so-called boring billion. This is this interval in the, it covers most of the, well, at least the middle chunk of the protozoic. So roughly 1.85 to 850 million years ago. So it's called the boring billion because of the fact that life is at a standstill in terms of, at least from a zoological perspective. I mean, nothing is happening, getting us to the kind of things that most people who are interested in biology would be interested in studying. So we're not getting the plants properly yet, we're not getting the animals properly yet. On the other hand, remember a lot of stuff that's really exciting does actually happen. So we build supercontinents, we have this massive expansion in the number of minerals that occur, probably something like two thirds of minerals come into existence, kind of leading up through this boring billion interval and we get the explosion of oxygen. It's still trace amounts, but geologically relevant amounts. You have these strange Canfield oceans, so these sulfur rich, low oxygen oceans and the evolution of sex is in here as well. So this is all super cool, but on the other hand, where we want to get to ultimately is dinosaurs. It's where everyone in the course like here wants to get and we're not anywhere closer to dinosaurs from the beginning of the boring billion to the end. Really, in any large sense. So remember that we've got book-ended glaciations. We're going to come back to that. The beginning probably is where we get eukaryotes. There's some geochemical evidence going back further, but 1.8, the beginning of the boring billion is a reasonable spot to put eukaryotes. We've got pretty convincing fossils around then, although the really convincing ones we don't get till several hundred million years later. But notice where animals are way on the other side, well into the next interval, which is the Paleozoic. Okay, so what else do we have? Well, the science has been changing pretty rapidly. Anytime I put together one of these presentations, I have to update it the next year because so many new studies come out. Sometimes I miss them, sometimes I don't, but I threw a couple in here. So 2019, we've got potentially the world's oldest fungus. There's a photograph of it right there. This is a bit contentious, but this is about a billion years old. It's Canadian, so I throw it in here. So about the same time, as remember, we have the world's oldest example of a brown algae, which is also the world's oldest example, therefore, of sexual reproduction. It's about the same time, about a billion years ago. This just literally came out in February. As you can see right here, this guy came out in February. We've got February 25th right here. We've got the earliest example of a green algae. So we've already got brown algae and now we've got green algae as well. This is not, again, super exciting stuff, but it's happening. What else have we got? Well, not a lot. That's the thing, not a lot. So what is holding up this progress? Well, there are a number of arguments, all of which are kind of three-step removed, kind of proxy geochemical arguments, but the most obvious thing that might be limiting it is just oxygen. So that we have geochemical evidence that suggests, although it's controversial, that oxygen levels were probably too low for the vast majority, and maybe all of the protozoic to actually support animals, even very, very simple animals. But of course, as I showed you before, this is relatively controversial. So here's a paper from 2015. Here's a paper that argues that, well, in the middle of that boring billion period, we had levels, so these are still low. You would suffocate at this levels, but as I showed you last class, this is still more than enough, more than enough to be able to allow a sponge to exist. So this is experimental evidence from Don Canfield and his team over here that suggests they need about 0.5% of the oxygen that we currently have to survive. Within the realm of likelihood for good parts of the Paleozoic, at least in certain water depths in the ocean, and yet we don't get sponges. Or do we? So when do we get animals? Well, as we talked about in class, it's not a super simple question. It depends on what lines of evidence we're looking at. So this is the diagram we looked at in class, and what I really wanna point out to you and remind you of here is that the actual hard evidence, and I mean literally physically hard evidence, the fossils you can hold in your hand, if you look at where are these things, where are these things, the earliest record we have, and this is a pretty recent paper, not the most recent. You can see that we're coming in here with a line which is really putting us right into the Cambrian here. Actually for a lot of these ones, the actual fossil evidence of earliest examples of these lineages is actually a little ways into the Cambrian. Now here you can see we've got sponges right here. Here's our sponges and this is putting it back using biomarker data. And in fact, the most reasonable biomarker data as we were just talking about is actually probably about here now, although there's some contentious fossil data over here now. But if we look at where the molecular clock data is putting us, right, the molecular clock data, that's suggesting that the origin of animals, the last common ancestor of animals is going all the ways back here, it was 780. And then the group that includes everything excluding the periphera, the sponges, the last common ancestor of that is sometime around 700 million years. So there's a massive gap, I mean this massive gap right here between where the actual fossil evidence ends and where the genetic clock evidence suggests that the earliest common ancestor might be. So big gap here. What I wanna talk about now over the next portion is this portion right here. This is the spot that we've been filling in fairly recently with fossils of, as you'll see in a second, sometimes confusing affinity, but at least fossil. We'll get to that in a second. But first I wanna show you what actually happens geologically as we move in here. So remember that we have a temporal change. We are jumping into named periods at this point. We're getting specific enough in terms of time that the intervals actually have names. So this first interval, that interval that the genetic evidence suggests that life might actually be showing up, that is the beginning of this interval here called the cryogenian. Then we're gonna go through the Cambrian and the Ediacaran. Last class we talked about the cryogenian. This class is really gonna be about these guys. So I'll just zip through, I'm just gonna zip through a quick reminder of what we talked about, the big changes. So the big thing that's happening here, and it's right here, remember cryogenian think cryogenically preserved, think freaky billionaires putting their heads in a freezer. That's the giveaway here. So this is a very cold interval. It's also this interval where we get a return briefly to bannered iron formations over here. So what is happening during this interval that makes it a cryogenian period? Well, what's happening is that the world literally freezes. And how does it freeze? Well, it's related, remember, to the breakup of Rodinia. So Rodinia was a giant supercontinent. The whole thing starts breaking up as it starts breaking up. That means you now have fragments of areas. It means you have more coastline. It means that within each thing you're now getting different weather. You're getting raindrops. Here's just supposed to be raindrops. So now you're getting rain inside, which means you get more rapid weathering. And you have coastline to bury this sediment in. So here's my chemical weathering. More chemical weathering means I fertilize the ocean, which means I grow plankton. More plankton growing means I'm pulling down CO2 from the atmosphere. CO2 is being pulled down. Literally the planktons are making their body of it. And of course you've got shoreline to bury all of that carbon in the form of organic material and limestone. So all of that is happening. And that leads to drawdown of greenhouse gases, which leads to rapid cooling. And that is the snowball earth events. So that is the basic story. And we went through that last time. Simultaneous with this, remember, we've got this mass igneous province, this huge interval of eruptions that are happening up in the Canadian Arctic mostly, but of course the world itself is not there at the time. The Canadian Arctic is not in the Canadian Arctic. The Canadian Arctic is hanging out right at the equator. And since it's at the equator, that means there's tons of rain, hot temperatures, which means the weathering of this material is gonna be really rapid. And the weathering of silicate, minerals, remember, pull CO2 out. And that CO2 can then come out to the ocean and bind up inorganically and form limestone. So all of that's happening. We get a drop in temperature. Here's a drop stone representing a drop in temperature and global glaciation. Cool, that's where we got. So we freeze the earth, there's snowball earth. But of course, while this is going on, we still have volcanoes erupting and they're shooting CO2 back up into the atmosphere all over. And eventually we build up enough CO2 that it overwhelms the impact of all of this reflective surface of all of our albedo here. And then we start melting the ice. So when we start melting the ice, the CO2 is gonna remain constant. But with less ice, that means we get a dramatic flip back to cold conditions. And so we get this flip around here. So that's the story. That is where we got up to last class. My slides don't wanna advance. There we go, okay. And we get this rapid flip back represented by a shift between here's glacial sediments and directly on top of them. These are the kinds of sediments laid down in tropical environments. So we're talking really cold to suddenly really hot. We lose our albedo, but we keep all of our CO2 so we get runaway crazy global warming. Cool. All right, so that is where it got us up to and where I left us off last time was here with the lie of evolution. What do I mean by that? Well, I showed you this video and I've given you a reminder here. I'm showing you this, I mean tongue in cheek. Don't actually watch this video. This video is a piece of garbage made by a creationist organization to try to play up a argument that evolution cannot be true because of what I'm gonna show you in a second. So the Darwin's Dilemma line, where does that come from? Well, a real thing that actually legitimately borrowed Darwin at the time. So even now, even now 150 years after Darwin or I'll say a hundred years after Darwin because part of what I'm gonna show you we already figured out about just over just over a hundred years after Darwin's death. So during Darwin's lifetime, as far as he could tell and any paleontologist could tell life just spontaneously appeared at the base of the Cambrian. At the base of the Cambrian period and there was just nothing before that. Just nothing at all. Now we know we have stuff before that but the stuff before that is not super compelling. So I mean, yeah, here's Banguomorpha, so we've got sex over here. I mean, that's pretty cool and you've got multicellular, it's a complicated thing, it's a brown algae, and we've got all these cool things, right? But it doesn't change the fact that at the base of the Cambrian, you suddenly get things that you would wanna scuba dive with. Again, if you went to a resort, apart from the fact that you'd suffocate, if you went to a resort 750 million years ago, you would immediately demand your money back because swimming with this thing, swimming with this, this is tiny, seeing a couple little brown algaes moving around on the ground, this is not exciting. And if they go, well, there's not much to see in the water but take a sample and come back to the microscope and I'll show you, there's stuff in there. You go, I still want my money back. It's not enough, I can drink. It's better be an all-inclusive resort. So that's where we work, that's where we are. And then suddenly, spontaneously, we get to this cool ecosystem with big things. So not only does this stuff look cool, this thing right here is about a meter long. I mean, this is a big organism. Maybe you wouldn't wanna go in this water because there's a giant meter long bug swimming around. This is a dramatic change. This is a really dramatic change to go from this to this. And it really did for a long time seem to be essentially spontaneous. So we call this the Cambrian explosion which is that during the Cambrian period, there is this apparently sudden dramatic increase in not only the amount of things that exists, but more importantly, the size and complexity of things. Whole ecosystems start appearing. So this really was an issue. This is from the ROM, the Royal Ontario Museum's website. You can see right here, here's the ROM. And this is the same kind of idea. So this is the Burgess Shale. I'll talk about this in a second. This is the most famous locality in Canada. It was the most famous locality. It's still probably the most famous locality in terms of Cambrian preservation in the world. But it was pretty much the only thing we had really gave us an insight into what animal communities were like at the time because of these amazing levels of preservation. If you go onto the ROM's website here, you'll take a look at 3D reconstructions, all sorts of stuff. It's a great website, anyways. These are the sorts of things you find if you go over to the Rocky Mountains and you go to Field, British Columbia, which is just on the edge of Alberta. It's right across the border. And you can go and see all this stuff over there. So that's the Burgess Shale. The new other cool areas in China, it's the Chenjiang locality and it's really amazing as well. There are other localities that are similar. And actually in the Burgess Shale, we now refer to the Burgess Shale not just as one particular locality, but we now know that actually around Field, the whole area around where that original locality was, there are strata that have similar levels of preservation. You Google things like Stanley Glacier, British Columbia, and you'll see some of the new discoveries in that park. So that's whole areas full of this stuff. But there are very few localities that show the material preserved from this time. Now, you get lots of things like trilobites, but what's amazing at the Burgess Shale is you get stuff like this. Like here's cyanobacteria, there's algae, and we get preservation on a cellular level sometimes. This thing here is an antelid worm. If you don't know what an antelid worm is, Google it, it'll freak you right out. This is a segmented predatory worm and you can see these are individual little filamentous hairs coming off of it. I mean, this stuff should not be preserved. In an ordinary situation, what gets preserved are things like shells and bones. Here you've got things like tiny fine hairs getting preserved. It's still a bit of a mystery what's going on. This specific, what we call taffonomic window. What it is that taffonomy refers to preservation and decomposition, the kind of study of that, in terms of the preservation of fossils. And trying to figure out exactly what is so special about these conditions is still pretty controversial. Take me a side and I, or send me an email I guess now, you can't take me a side. And I'll take you through it if you want, but it's beyond the purpose of this lecture. Here's some more shots. So this is a, this is an arthropod, but what I want to show you that's super cool is that not only do you have shells here, but you've got things like that as the antenna coming off of it. And the use of the legs coming off of it. These things ordinarily do not preserve. This bit here is probably the gut material actually being squished out after this thing died right here. And I mean you just get thing after thing after thing like this. Here is a brachyopod. This is normal. That's a shelled organism. That's normally preserved, but these little hairs coming off, this is stuff that would stop it from sinking into the soft sediment. This increases its surface area like a snowshoe. This stuff just does not preserve. Here is a soft bodied organism where you can see there's eyes on here. I think that's the eye there, but I might be wrong. And I think this is interpreted to be the radula which is the boring instrument that things like snails have that rasp away. You can see actual, these are I think muscles in here. That's a gut track I think, but I could be wrong. I'm not a Cambrian expert or a melocologist, but there you go. So you can Google this if you want. This is purported to be, it really is a mollusk. It's a little bit controversial. This is a just absolutely spectacular example of a velvet worm. We talked about these in class again, but again, this is the kind of thing, there's nothing hard here. This shouldn't be being preserved. This is a freaking jellyfish. This is a comb jelly, again, perfectly preserved. There is a sponge. This thing is super neat. I actually had a dog that I called this. I called it Pikaea, my dog. It's actually Pikaea, I believe. I got corrected when I went to the ROM one year. The curator there said, oh, I believe you mean Pikaea. Pikaea, I can't actually honestly remember which is Pikaea, I believe. My dog was called Pikaea because I'm a nerd, but apparently a nerd that's not good enough to get the pronunciation right. But what's important about this? You see this backbone-like thing here. This is a notochord and you can see musculature along here. This thing, if you look at it, looks like an eel and it was. This is something like a very, very primitive eel. This is interpreted to be a cordad. Phylum cordata is the phylum we're in. This is us. This is one of the earliest known ancestors of our actual group, the thing that makes up everything with the backbones. This is remarkable. Here is an example, again, of the arthropods. These are some of the more abundant organisms that show up in the Burgers shale. This is that one meter long thing, anomalacaris. Waxia. This thing's super weird. I'll show you some reconstructions. So this is hallucinogenia. You saw this in the video early on. This is, again, we think it's now a velvet worm, probably. Anyways, if you follow this link here, you can see the link right there. If you want to type it in, I'll hold it for a second. But I'll put the PDF up as well. Yeah, PDF, I guess. And I'll put an active link in there. You can follow it up. There's amazing links. The ROM has a fantastic website. The reason for that is that the ROM has been for the last, I don't know, 50 years or more than that. They have been essentially the only group, maybe even actually the only group that actually has access to the Burgers shale. Because it's in a national park, they have a long standing relationship with the park that allows them essentially soul operation within the park and also essentially soul curatorship. There's a research group at Cambridge. It does some stuff. They've got materials, a bunch of research groups. So really the ROM is the main spot. If you want to study Cambrian stuff, you can't play a better place in the world to do it than that. The University of Toronto, which is where the curators are cross appointed from the ROM. All right, I want to move on. So let's getting back to Darwin's Dilemma. And Darwin's Dilemma, here he is, spelling it out right here, right? To the question of why do we find not? Why do we not rather not find rich fossiliferous deposits belonging to these assumed earliest periods? Those are pre-Cambrian periods I can offer no satisfactory answer. The case at present must remain inexplicable and maybe truly and may be truly urged as a valid argument against the views here entertained. So what he's saying is that this is legitimately a argument and one that he does no response to, right? This is legitimately an argument against his argument for natural selection and evolution, right? This is, and he says it's inexplicable. He's got no good explanation for what is going on here. So we will make him sad. Let's make Darwin. He already kind of looks sad, but let's make him very sad. All right, so this is Darwin's Dilemma. And this was certainly the case in 1859 when Darwin wrote the Origin of Species. Now, to give away the rest of the lecture, it is decidedly not the case now. It is decidedly not the case. So let's take a look at how things have changed. So that's what the Discovery Institute, which are the guys who put that video out, would like you to believe. It's just a mystery. Supernatural powers did it and you can go home. So that's not the case. So here is the increase we've got. Here's the Cambrian, right? There's this increase and we get this. We do really have genuine, I'm gonna revisit this, genuinely a massive increase at this point. I mean, it's absolutely greater life at this point. But remember that we've got the Ediacaran leading up to that. So here's the Cryogenian. This is his interval. We've got these massive glaciations. Notice we've got another little baby glaciation here. The Gaskier's glaciation right at the, more or less, not at the end, but pretty close to the end. I guess it's actually more of the middle of the Ediacaran. So that's really kind of the end of this Snowball Earth glacial episodes. But the big guys are here. They're in the Cryogenian. All right, so that's just to give you some historical context or some temporal context. So let's move forwards. The Ediacaran period starts at 635. Remember that number. I'm not gonna have you remember a lot of specific numbers, but just for the rest of the lecture, remember 635. So we're gonna move on from there. The end of the Gaskier's is around 580. Remember that number as well, roughly around 580. So we end the Meronian glaciation, the big glaciation, which ends the Cryogenian. We end that at about 635, and then we end the Gaskier's right over here at 580. Bear those in mind. We're gonna move on now. And we're gonna talk about specifically Metazoans. So complicated life, animal life. We're bringing on to these guys. So here's our diagram as well. And remember that the molecular evidence suggests that somewhere, right? Somewhere right around, right around here is where the stem of all these things would be, right? Right around here. And you can look at back where we are, right? That's gonna be right in the middle of the Cryogenian. Or in the middle of a big glacial interval at that point. This boundary right here, you can see molecular evidence says we should have an interval of rapid diversification. We start producing the ancestors of all, a lot of these big groups over here, should be occurring in there. Again, it says a molecular evidence, but this is a long time before we get any fossils, okay? So that is where we are. Let's jump forwards. Here is what's happening during the Edeachryan. So we're gonna talk about this interval after the Gaskiers, roughly around 580. But I wanna note that although stuff gets really cool after this, stuff's happening, right? During this entire interval. It's actually happening all to the Cryogenian as well. So what's happening? Well, nothing again you'd want to scuba dive with. But if you look at microfossils, if you are a micro paleontologist where people look at microfossils, what you're gonna see is a steady increase in not only the number, right? The abundance of microfossils. But importantly, the complexity. They start getting cooler as you go on. So you get stuff that looks like this. You get stuff that's all spiny like this thing over here and spiny like this stuff. A lot of the stuff we don't know actually what it is. A lot of these were probably the cysts of the resting stage of other simple organisms. But then you get stuff like this that are potentially kind of embryos of Metazoan. So these might represent potentially the embryos of primitive Metazoan life. So maybe a bit controversial, but you've got cool stuff happening throughout over 200 species, right? We keep adding to them. So this increase in complexity is happening all through the Edeacria. But you still don't want to scuba dive with it. So when do animals show up? Well, as with everything in this course, when we're way back in time, the further back in time we go, this gets you the evidence gets. So this is a relatively dubious thing. It's sort of like a sponge. So this is the earliest kind of purported actual fossil of a sponge. This is a paper from 2012. You can check the link out in the PDF. This is at 760. So this puts us right dead in the middle of that interval of glaciation. Notice though that remember that we were around 700 million is where approximately the genetic evidence was saying we might be based on those molecular clocks. So that's not crazy relative to this. It would still actually be fairly early, even relative to the, where we'd expect from the genetic evidence. So this is a more realistic looking fossil and it's still controversial what the heck we're actually looking at. But this thing, by the way, this is about the size of a grain of rice. This thing is super small and is one of them. This is a 2015 paper to the best of my knowledge. They've never found any other ones after it. And this is interpreted as being a sponge. A sponge. This is a sponge that has a good time. That's a sponge. And this is at 600 million years. So remember that final glaciation around 580. Remember that and we'll come back to that. Remember that the ediacary in starts properly around, starts properly around 635. So that's where we are. All right, this just came out super recently. This is 2018. And this is a biomarker paper. So thinking back when we talked about the origin of life, it's a biomarker paper. What's a biomarker? Remember biomarker is a organic or is a chemical molecule which is specific to a particular kind of life. And in this case, this big thing here that I actually asked the PhD chemist in the other room, how to pronounce and I forget already. I think it's 26 methyl stigmastane. This thing is something which is specific to this higher order of sponges right here. So this suggests that by 635, which is the very base of the ediacary, and this is from Oman, which is the country in the Middle East, we've got sponges. So we never had a fossil, a convincing one this old, but this is pretty reasonable evidence. Although remember that you can contaminate with, it's much easier to move molecules between layers of rock than it is to move fossils. So there's always that argument against biomarker data, but this would put the origin of animal life in at least a simple sense at the very beginning of the ediacary. Okay, so that's where we stand as of today. This is still not convincing you that the Darwin's Dilemma has been solved, but that's not all we've got. And in fact, the new stuff here, although it pushes back the line a little bit, is not even the most convincing part. So I guess the first thing to talk about is what might be happening during this interval. Well, first, what was holding off evolution during that boring billion kind of time interval? Well, we talked about oxygen potentially, we talked about molybdenum, various things that are limiting factors, chemical limiting factors within the oceanic realm, is probably what was going on. So what might have changed then as we move into the ediacary? What might have changed if we actually get sponges showing up and sponges are animals? They're really simple animals, but they're animals. What might be changing there? Well, possibly snowball Earth itself. Remember that we've got these big snowball, this is the end of the last snowball interval right there, and immediately thereafter, we get apparently, based on that biomarker evidence, we get sponges showing up. And then remember, this is another last little guy here at the end of the gas gears, and I'm gonna show you in a second that we start getting embryos showing up and then we actually get incontrovertible animals and cool animals showing up right after this thing. So what is the association between these glacial events and the rise of animals? Well, maybe nothing. I mean, this could just be a coincidence. It could just be that evolution was turning along in the background and then it just happened at this time. Far more likely, it's not a coincidence that one of the great geological events, this snowball Earth interval, happens to be happening at the same time as we've got the evolution of animals showing up. So what might have been happening? Well, these are a couple of papers that have come out relatively recently. This is a 2010 paper, and this suggested that the erosive effects of the glaciers themselves may have led to an infox of phosphate. And if you guys have done any gardening, you know that you need phosphorus. It's one of the key nutrients that pretty much all life needs. So maybe there wasn't enough phosphorus in the world's oceans and that was actually limiting the production of phytoplankton and things, which is then limiting the total availability of energy for larger animals to eat. If there's not enough food, then you cannot get big. There's nothing to eat. So that's one possibility, or maybe oxygen levels jumped up. And how might that have happened? Well, it could be that hydrogen peroxide was building up in the ice, and then when the ice melted, all that hydrogen peroxide is released, and that then broke down and released oxygen. And that could have been happening. That was in the video we watched. So those are a couple of ideas. There's a lot more of these things going on. Again, it's all geochemical arguments two-step removed. But these are plausible ways that this association temporally between these glacial events and this explosion diversity first of microfossils and then later on of animals, really cool animals, and sponges in here as well, we now know. That could have been driven actually by changes, geochemical changes that happened as a result of this major geological event, snowball earth. Okay, so what else is going on? Well, another thing that's going on is that we start to get pretty strong evidence of oxygen seeping deeper down. Remember that for most of the Paleozoic, oxygen was restricted to relatively shallow water environments, so nothing could actually live down in the bottom, and which is where a lot of life lives today. So we seem to be getting a deeper penetration of oxygen during this interval particularly after this last asker's event, but I mean kind of throughout this interval. So what might be going on there? Well, this is a really neat example, again, of something that I've emphasized a lot in this course, which is the feedback between abiotic and biotic events. So you've got life showing up, pumping out oxygen, which interacts with methane, forms ammonia, and pulls down greenhouse gases, causing the erronean glaciation, we saw that. We looked at life pumping out oxygen actually by introducing oxygen into the atmosphere, increasing weathering, which led to the runoff of the breakdown of sulfide minerals, which led to sulfates pouring into the ocean and the rise of the Canefield ocean. We've seen these kind of feedback events where geological events are actually being led by biological events, and so this is potentially another one as well. So what happens when you get a sponge? This is a really neat idea that a guy named Nick Butterfield, he does a lot of Cambrian stuff. He's at Cambridge still, I think. Ah yeah, University of Cambridge as of anyways, I think this is 2015, maybe I stole this from. This is a conference presentation, but if you follow these links, there's a bunch of discussion about this, of the role that sponges in particular may have played in boosting O2. How is a sponge gonna boost O2? They're an animal, right? So they breathe oxygen. They're not putting oxygen out there. Well, the way they might have done it is not by producing oxygen, but by stopping the destruction of oxygen, which sounds a bit weird, but I'm gonna show you a video that's gonna illustrate this point really nicely for you right now if this starts. And I got this from, here's the credit down here. You can watch the rest of it. So this is a non-toxic dye. It's not hurting. It's not actually hurting the organisms at all. Let me just turn that audio off. I'm not sure if you could hear that, but just in case. So they're gonna put some dye next to this. And what I want you to see is what happens to the dye. Let's go forwards a little bit. Jump forwards, there's the dye. And he puts the dye around. So the dye is around the outside. Now watch what starts happening on the inside of this thing. You see that jet coming up there? So you couldn't see it before until you had the dye, but there is a steady and continuous stream of water, which is rushing out of these. And that's because the sponge itself is pulling water in through this. The outside of this acts kind of like a Brita filter, right? The entire sponge itself is kind of like a Brita filter. And that water goes through it and everything things that are floating in the water are getting pulled out and they're feeding the sponge. That's what the sponge is doing. And then it has to get rid of that so it shoots it out the end here. But the action's actually happening in the wall of the sponge here, which is perforated, right? And it goes through, right? And then pulls out any kind of food particles, little tiny bacteria and things that are in it. They're getting pulled out, which means that what's getting shot back out has been filtered. Just like a Brita filter, again, filters water, the sponge itself is filtering water. So just like you would rather drink water from a Brita filter, it's better to have an ocean which has been filtered. Why would that be the case? Well, the reason that's the case is because, the reason that's the case is because, this is gonna be kind of a pain to move between my videos now, I think. Let's see. Yup, it is, all right. Well, there we go. I can't go back to show you. I'll just have to tell you. Maybe I can draw. Let's see if I can draw a picture here and get rid of it. So the reason that is the case, remember, is that where you've got bacteria or any kind of organisms and they fall down and die, they are gonna get broken down. They are going to be decomposed, right? I can't write decomposed, I was right. They're getting decomposed by other bacteria. And in the pros of the decomposition, they are using up oxygen. So the decomposition of life itself uses up oxygen. So goodbye, oxygen. So we talked about dead zones. You remember famously in the Gulf of Mexico every year, the over-fertilization of the Gulf of Mexico from fertilizer runoff, from the overuse or abuse of fertilizer on crops all the ways up along the Mississippi. It flows into the Gulf of Mexico. It fertilizes the phytoplankton in the ocean who then die, get broken down by bacteria and they then use up all of the oxygen in there. So the idea is that by removing, right? By eating up, literally, bacteria and tiny little microorganisms, right? They are limiting the amount of material that can then be decomposed. The other thing they're doing is literally circulating the water around. By circulating the water around, they're helping to bring, they're helping to move around oxygen because they're moving around water. So one little sponge is not a big deal. But think about a trillion sponges doing that. That's suddenly gonna start moving a lot of water. And sponges don't just live in shallow water. They live in relatively deep water as well. So you suddenly put them in as engines, right? And the floor of the ocean all over the place. And suddenly you start getting a new, powerful kind of convective force moving around water and simultaneously cleaning it up and therefore helping to retain oxygen. So that's the idea. Now here's another thing. This is a paper that just pretty recently came out, 2018. And this one here, these are all proxies here. But the one I wanna show you right here is these drops. Each time this drops down right in here, that is proxy data that is suggesting that there is a major drop in the amount of oxygen. And I want you to know the time intervals here. Right here around 542. And then you've got another important one in here. So look at the words, small shallies, and look at the words, idiotic or anti-biotic, we'll come back to that again. But the idea here is that you've got a lack of oxygen. A loss of oxygen, oxygen fluctuating, which is driving extinction events here. So maybe the addition of oxygen over here is what's actually allowing the expansion of these organisms that we're gonna talk about later on. But I'm gonna come back later on to this idea of oxygen-driving extinctions. Anyways, let's move on. So I wanted to get you to see to the meat of this stuff faster. But here we go, here is the meat of it. 37 minutes in, not too bad. Halfway through the class. Actually it's about halfway through the material as well. Okay, so here is a diagram. I don't remember where I pulled this from, but the link's down at the bottom. Again, take the PDF and all these links are live. So this word over here, you have already seen it. You've seen it in the form of a period. So idaachrian, that is a place. It's also a unit of time, the idaachrian period. And it's also a descriptive word for the animals that lived during that time, right? The idaachrian period right here, which were first described and discovered in the idaachrian hills. In, maybe I think it's just the idaachria hills in South Australia. So they are super weird things. And I want to show you that they first start showing up. And here are the first examples of them. Are these kind of guys over here? Let me make this guy smaller and I'll get rid of all, get rid of all these things here. So this interval right here, around 575-ish, is when you first start getting up this thing here, charnia. And charnia is a really famous thing here. There's a bunch of these things, charnia discus. Charnia is a different species of these things. So I want to show you, it's not responding again. Come on little guy, move forwards. All right. Mmm, thinking about it? This is when I would let you ask questions. This is one of the things, in a live classroom, when things don't go wrong, you can just fake it. Is it teaching trick for all you be ed majors? Is that anytime something technically goes wrong, you just flip to active learning? Not only is it a good teaching methodology, but it's a really good way of covering up for, ah, there you go, stuff like this. So when I say first phase, second phase, this is my terminology. Actually, the Acherian workers, they divide these things up into these assemblages you see over here, Amelot assemblage, White Sea assemblage, Nama assemblage. These are associated, this is Nanibia, I think. These guys are mostly associated with Australia, and these guys are mostly associated, it's famously associated with Newfoundland. So they have ways of dividing this up. When I'm talking of these phases, this is my terminology, I wanna emphasize that. This is not technical terminology, but it's describing important things that are happening. So I want you to see first off, these guys here who show up first that are in the blue, the vast majority of these things go extinct at about the same time as all this stuff starts showing up. There's overlap, right? Some of these guys do cruise through, some of these guys cruise through, but you can see that the kind of things you would find in this interval of time are different than the kind of things you would find in that interval of time, and I'll explain why. Then I wanna show you this guy here, Claudinia. He shows up right here in this third of interval of time, when almost all of the rest of this stuff goes extinct. So you have an extinction event here, essentially. Another extinction event right here, okay? I want you to bear that in mind. Now look at these guys here, you see these weird looking guys, these guys are also weird looking, but they are very different. In particular, I want you to look at Kimberalla here. I'll show you him in a second. So leading up through, leading up through the, leading up through the Ediac, when we start off with these increasingly complicated trace fossils, trace fossils, sorry, microfossils, we get these things here that are probably embryos of metazoans. Right here, this line here, we have geochemical evidence for the earliest sponge, right about here-ish. We've got the earliest sponge fossil, and then right here after the gaskier's glaciation, suddenly we get that thing showing up, which is, it's one of those. And we get these things showing up a little bit later, and they are some of those. And then finally we get this thing, which is, you know, it's one of those. So I'm not being coy. We really don't know what most of this stuff is, and I'm gonna show you that in a second. You can try to take some guesses on what the heck you think this stuff is. So let's look at the rangium morphs first. These guys here, these guys are the rangium morphs. These are the Avalon assemblage. These things, these blue guys over here. Most famously, things that look like this. So these things are most famously located right down here on the southern tip. If you take the ferry, you know, you go in here, the ferry goes here to Newfoundland, and then you drive around. You go to St. John's. Most people either do that, and then, you know, fly out, or they fly in and out of St. John's. They don't know that they're just this far away, especially if you take the ferry. Maybe the other ferry goes out of here, I think. You are this close to a pretty amazing spot. It's an amazing enough spot that it has been recognized as a site of global cultural significance. That's what a World Heritage Site is by UNESCO back in 2016. It's also just spectacularly beautiful when you go there. You can walk along the shore. I'm gonna show you a promotional video that really brings us home in a second. So let's see if this will load. Okay, so I'm pretty sure you can hear the audio. So what you can actually do is just pause right now and just Google secret place TV ad or just secret place or Newfoundland, secret place, Newfoundland, mistaken point. Any of that ad will get you on YouTube. Watch that, pause this video, come back to the video. And be moved to tears by the beauty. It's just honestly, it's a remarkably beautiful spot. Even if you just went there and there weren't fossils and there are, it's such a spectacular spot that it's worth visiting anyways. But now we know it is this amazing locality that you can go see, right? Here they are and they're everywhere, everywhere, right? Literally everywhere. And there's over a hundred bedding planes like this completely covered. Each one of these things is a something. And what do I mean by something? I mean, it's one of these things. So there's one of those and they kind of look like that. We call these spindles and this one's called the pepperoni pizza because they don't really know what the heck they are. So these things here that have this morphology like this, there's a different one, there's one. These things are all called rangiomorphs, right? So there's your rangiomorph. It's possible I'm not pronouncing that right. Never actually heard an ideocrine worker say that. So apologies if I'm not pronouncing it right. And here is a reconstruction of what one might have looked like in life. And this is based on this thing here, which is also from Newfoundland. I think they actually found this as a beach of, rock just lying on the beach, if I'm remembering correctly. Read that and double check it. This is Guinar Boon. He's a paleontologist at Queens University in Ontario. Anyways, this gives you an idea as a three-dimensional one. And the cool thing about this, if anyone's mathematically inclined to see, these things have a fractal form, which means that it's a reoccurring geometric arrangement at every level. And you can see that here where the overall branching form is also represented by this branch and then that branch and then branch and then a branch and then a branch and then a branch and then a branch. All the way down. So what were these things? No idea. No idea. We don't know. They're arguably animals. They don't have mouths. They don't have guts. They don't have anuses. If they ate and they had to have eaten because they are found in this locality in deep enough water that there wouldn't have been enough light down there for photosynthesis. So that means the only way they could have lived is if they were just absorbing nutrients straight out of the water, which is not actually a crazy way of getting around. And especially if no one else is competing for you at the time, these things importantly do not fit in with any other group that's known today. These were an experiment in the earliest days of the evolution of probably animals. Although some people disagree, that was a failure. These things went nowhere. But this was the first big step in the Edeachryan kind of revolution of an evolution. So here's your enkeomorphs. Here's another paper. This is another one from the UK. They're famously in the UK as well. It's actually where the Charnia comes from. Charnia forest, I think it is. I wanna really emphasize that this thing is not remotely related to this at all. These are completely different organisms. This thing has no gut, has no nothing. This is a thing called a C-Pen. I just wanted to show it to you to give you an idea of what this thing was probably like when it was alive. So this thing here would have been a disc where it attached on the ground. It had a stalk and this would have stuck up in the air. And so it would have had a similar lifestyle in the sense that this thing held itself up, this fron-like thing held itself up and absorbed material out of the water. Except in this case, it's actually filter feeding. In this case, there's no sign that it was able to actually do anything other than just absorb straight through its skin. So this is a exemplar, kind of an analogy for what this thing probably would have been like when it was alive. There's been a bunch of work at mistaken point since they discovered the community there, including things like looking from an ecological perspective. And what you see is just like if you go to a forest today and you see tall trees and then below the trees, you see smaller things and eventually you see grass on the ground. And that's because if you're competing for resources, in the case of trees, you're competing for light. In this case, they're competing to absorb material out. If water is going by, if this guy's stealing all, you know, this guy's stealing all the nutrients of the water down here, it's a good trick just to grow above him and then you can get the water he's not getting. And then you can grow above him and you can grow above him. And so this is, we call it trophic tiering, which is a division of an ecosystem into literally different heights to access things. So you can see that kind of thing there, where we have different levels of an ecosystem in terms of the harvesting of food. And that's something you see in any modern ecosystem today. You already see that, you know, by 565 million years ago. So this is, remember, the kind of mid to late Edeacurin. Number five, or 635 is when we start the Edeacurin. So here's another thing. This is 2014, there's 2014, 2015, two papers scale them out back to back and it's this glob here. And what is that glob? Well, if you spend a lot of time looking in a microscope, what you see are these kind of branching things that come off of them and then these strands that go in different directions. Some of them are long and skinny. Some of them are fat and short. And those are exactly what muscle fibers look like. When you contract a muscle fiber, it is long and short and fat. When you let it relax, it's long and skinny. And so these are interpreted to be actual muscles. And this thing is the reconstruction of what we think it was like. The kind of tentacles coming off here and a cup shaped thing like this. These, this reconstruction looks remarkably like this thing right here. This is a stocked jellyfish. If this will load, we'll do some cool stuff. So there's a stocked jellyfish. So within the ediacarian assemblages at mistaken point and the surrounding layers, what have we got? Well, we've got some of the earliest examples except for the sponges of life. We've got the earliest examples of communities. We've got these really diverse communities and abundant communities. Doing something, right? Living down deep underwater, absorbing presumably nutrients and looking like nothing that's alive today. So let's go back to the Ediacaria Hills. These are in South Australia. They're off here somewhere. And there is a site. They don't tell you where it is. It's kind of hidden because they don't want people going and taking this stuff. This is where this material was first discovered. And this is the point really where Darwin's dilemma got destroyed. And we've had these for quite a while. I don't remember. I think it was the 1950s. You could Google that. These things were discovered. And they look like this. So the first thing you might notice is these do not look like the Rangiomorphs. They're not. These things are a little bit younger. They are very different things. They're those phase two organisms we were talking about. On the other hand, they still don't look like anything that's alive today. They look super weird. Like that's one of those things. What the heck is that? Well, some people would say it's like nothing. Literally, it's nothing that's alive today. Other people say maybe it's one of these. Maybe it's like a coral like this. Or maybe it's like a really primitive polychaete worm like this or maybe it's something else. We don't know. It seems to have been three-dimensional. They seem to have been just essentially sacks that just sat on the ocean floor as near as we can tell. And here's one of these things. This is triberchidium. Why is this thing so weird? Because this thing has three-fold symmetry. So for all the biologists in the world, you're going what? You're having a mind-blowing right now because nothing has three-fold symmetry. We have bilateral symmetry, which means you could cut us directly in half and you get two parallel things. If you run a line that goes straight from the top of your head down the bridge of your nose and runs straight through separating your ribcages, you get two identical mirror images. If you get starfish, they start off with bilateral symmetry and then they get five-fold symmetry later on. This thing has three-fold symmetry. Again, nothing alive has that. So this is probably unrelated to everything alive. We don't know how this thing made a living. It just seemed to lay on the ground, once again. So these things were weird enough that this guy here, he's now unfortunately passed away. It's a guy named Dolph Seiliker. He was a very famous acknowledges. It's a guy who studies trace fossils. If you can ever name an acknowledges, and I'll be honest, I can't accept Dolph Seiliker. I feel bad about that. I should follow a couple on Twitter. Apologies if you're listening. He actually argued that these things, he gave them a different name. He called them the Vendobionta. He thought they were a completely different evolutionary experiment, where life just tried something out and everything died and nothing made it on. So this is, he's a bit of an iconoclast. He came up with some controversial ideas in his day and pushed the field in a lot of different ways. We think he's probably wrong. This thing actually maybe was a real experiment. This thing maybe was a real experiment, but some of them actually look pretty familiar. So here is this thing I told you to remember before. This is Kimberella. So if you look at that right now, you're gonna go, Jason, that's just a little smudge. What the heck is that? Then I wanna show you that thing. That thing is a thing called a nudibranch. That's essentially just a snail. If you take a snail's shell off, I mean, it pretty much literally is, it's a mollusk. So I'm not saying this is a nudibranch, but we now think that most likely this was something that was nudibranch-like, a very simple, primitive mollusk, is how this thing is being interpreted. Most likely right now, it's still controversial. And you get things like this. This is Sparginia, or Sparginia. What is this thing? Well, notice that it has, at least it appears to have bilateral symmetry. I think the symmetry is not actually perfect on this. All this stuff's still a bit complicated, but it sure looks like it's got a head and a tail, right? It looks like it's got a head and a tail down here. And it also looks a lot like a trilobite, which we'll look at later on. So could this have been an early arthropod? The group that includes things like clams, or clams, crabs and lobsters and cockroaches and pillbugs and things like, maybe. That's how it's been maybe interpreted. Most plausibly interpreted, but we don't really know. But there's a lot of this stuff, anyways. There are over 100 different genera at more than 30 localities, most famously at the Ediacria Hills and in mistaken point. But all around the world, we find these things. They lived in deep water, like the ones in, like the ones, the rangium morphs in mistaken point. They also lived in relatively shallow water communities, like the ones in Australia. So we have them in different ecological areas, doing different things, radically different morphologies. And all of these things are existing through an interval, leading up in the kind of, you know, 40 million years plus leading up to the base of the Cambrian. So this is a solution to Darwin's dilemma in that we've got clearly an evolutionary lineage that goes back before the beginning of it. But as I'm gonna say in a moment, it's not a complete, at least satisfying explanation. So here, remember, is our story again. This is the end of the cryogenian, 635, earliest molecular evidence for sponges. We get all the microfossils start going crazy here, some evidence in terms of embryo fossils of probably metazoans. An earliest example of a actual convincing, a relatively convincing sponge fossil is here. These rangium morphs show up here. Slightly thereafter, you start getting these things that actually start looking some of them anyways, start looking more like things that actually we know what they are, right? And then they all go extinct. So we get an extinction here, we get an extinction here, and then that's corresponding with these guys here. Okay, bear that in mind again. So goodbye, Edeachry and Bioda. And more importantly, essentially, either none is again a bit controversial, but pretty much none of these things make it past the Cambrian. We get a whole-scale extinction of the Edeachry and Bioda at the end of the Edeachry. So what is happening? What is happening at this point? Well, before we get into that, I want to show you what the other thing that's happening during the Edeachry. So not only do we have life showing up, and some of it gets pretty big. Some of these things are like a foot long or more, but importantly, we start getting evidence of trace fossils. So remember, we had two different classifications of fossils, body fossils, which are the actual animal, and then trace fossils, which are things like footprints. That's supposed to be a bird or dinosaur footprint, right? I'm going to make another one so it's more clear, another one. That is not the organism itself, but rather that is its record of its activity. So this is a trace fossil, and this is the kind of thing that a worm might do. If it went cruising along here, it's going to lead a little line. If you've ever seen the tide out, and you've seen where snails went along the sand, you've seen this, right? So we start to get trace fossils around 555. They start off really simple, just simple feeding structures, really simple shallow burrows. So I'm going to show you where 555 is in this scheme. So let's jump back one. Let's get rid of this guy and we'll jump back one. So 555 is putting us where? That's putting us right here. So things like this, if this is a mullet, they're starting to cruise around. So why might that make a difference? Well, I'll show you in a second, but these things, remember, it is lying flat on the ground, and a world where things are zipping around, all over the place, is going to be a very different world. Okay, so let's go along, and we'll show you one more big change. These are some, actually, kind of bad computer-graphic-y things. This is a reconstruction of a guy called Nama Calathus, and this is a late Ediacarian fossil. This is a reconstruction from a book called Four Millionaires Encounting, which is fantastic. This was what we thought these things looked like until relatively recently. This is a more recent reconstruction of one, and this one is from Namibia, and in this case, they actually had three-dimensional preservation, and importantly, they actually could do sections of what its actual body was like, and now they're interpreting it as something which is actually like a brachyopod, and a brachypod. You guys don't really have to know. Later on, we'll talk about brachypods. They look like clams, but they aren't, and this is it budding off over here, and they've got these tentacles, so it's a much more complicated animal, but the important thing that distinguished it is in here. This is the part that's making it be a little bit of a foray as well, and we already knew about that over here, and I'll tell you what that thing is in a second. It also co-occurs with this guy right here, and this is more like what you're probably used to thinking about when you think about a fossil than all that stuff I showed you in the Burgess Shale. So these guys, Claudinia and Nama Calathus, they show up together in the same beds, and they both are using the same trick, which is an amazing trick, which is that they are building parts of their bodies out of minerals, and that might not seem like a really cool trick to you. I mean, you do it, and if you take a moment to pause the thing and tap your teeth, maybe don't do that, it's unhygienic, and you can see that you have mineralized material in your mouth. In fact, the entire structure of you, your internal structure is skeletal. It's made of calcium phosphate, your muscles attached to that and work as levers to power you around. If you pick up a clam, you can't get into the clam's guts because it's got a shell around it. This is, and this is, the earliest evidence where we actually start getting organisms that have clearly learned the trick of building minerals around their bodies, which means that they have started to armor themselves up, and they now have the potential to do what? Build armor, build teeth, and build internal skeletals that you're gonna attach muscles to. And that is gonna be dramatically important. So I wanna show you this guy here. So this is a thing that kinda looks like a coral, probably wasn't, but it's something like that, something spongy-like, right? It's building an outside, an exterior, which is made of, I think this guy's made of calcium carbonate, you can Google that. And importantly, you see that right there? If you ever walk along the beach, you pick up a clam shell. You'll sometimes see these at the top of a clam shell, very similar. So if you imagine this is a clam shell, this is like a scallop, it's ribs coming off like this, it's a terrible drawing. But imagine that's like a scallop, that's the hinge of the shell up here. You'll often see a little hole right there. And those are drilled by snails. They come along, they sit over top, and they use that thing we talked about, the thing called a radula, and they literally just drill straight through and they cut the muscle inside and they open that guy up. So they use that to get inside. What is that? That is a drill hole. And what does that mean? That means something was attacking this thing. So in this fossil, we have two of the most important things you are gonna see in this entire course, which is one, learning this trick right here, learning this trick right here of transforming or pulling dissolved material out of the water and building a shell out of it, which can act in this case like protection. And why might you wanna do that? Well, look, something is trying to eat you. Until this point, nothing was trying to eat anything. Importantly, until just briefly before this point, nothing could try to eat anything because literally nothing could move. Nothing could move. Nothing could move along the ground. Remember that we only have the first fossil evidence of things moving along the ground around 555. So simultaneously, we're getting evidence of things moving along the ground, cruising along the ground. We're getting evidence of things armoring up and we're getting evidence of things attacking. And that creates a world which is a lot more like the world we are in right now. This is, at this point, this is a garden of Eden. Everything's just lying back, chilling, just pulling nutrients directly out of the water. As we start transitioning into here, here's our Claudinia showing up right here, right? This is an interval where suddenly things are attacking each other, right? This is the nature, red, and tooth and claw that Darwin was talking about before, right? He actually didn't use that terminology, but that idea. This is a war of things fighting each other, right? Till this point, everything is just lying right happily next to each other. Nothing's doing anything to itself. At this point, predation starts showing up. And we'll come back to that point in a second. So here is that point really well illustrated, right? That these are Canada's oldest Shelley fossil deposits. These two guys together and they are Shelley. You can go read this article if you wanna read about where these are in British Columbia. All right, so where is that placing us in our timeline? That is placing us where? Let's bring our little thing up. Let's bring our guy here. So here is 542-ish. This is the base of the Cambrian period right here. So we get evidence of locomotion, predation, and the earliest shells all flowing right here, right at the base of the Cambrian. And then all of that Ediacrian stuff goes goodbye. It all goes extinct. And as we showed you earlier on, there is some evidence there's a shift in oxygen that's happening at this point as well. There's also an evidence of a shift in oxygen around the time that those other earlier Ediacrians died, but it cannot be a coincidence that we're also seeing locomotion and predation showing up at the same time. And I'll revisit that idea in a second. So we still have what? We've got this massive explosion though over here. You see how this increase in diversity, wah, like this going off the charts. Now we have lit a fuse that goes all the ways back here. And it goes back if you go with the geochemical evidence, it goes back to 635 for the earliest, the earliest, earliest sponges until we get, you know, here that's going back almost a hundred million years. So in that sense, we have gotten rid of the Darwin's Dilemma. We have solved it, right? We've solved it. On the other hand, this still requires an explanation. You still, I'd go scuba diving in an Ediacrian collection, but that's because I'm really interested in the, I mean, I would love to see what Arangium Morph really looked like alive. But this is a really cool community. This is something that if this existed today, you today as a non biologist would want to go scuba diving in this. So we still have this dramatic change which is taking place right here. So at the base of the Cambrian itself, we see this start happening, right? It's a continuation of what we saw before, but we start to get trace fossils that are getting geometrically more complicated. And what does that mean? That means the behavior is getting more complicated. And importantly, they're going into the ground, right? So they're starting to get into the substrate itself. In fact, literally the base right here, where it says GSSP, right? That is global stratigraphic, oh my God, point. I am blanking right now on GSSP. We call them a golden spike. It's the point that delineates the, it delineates, it comes to, it's the standard that delineates a point in time. Just like we pick individual organisms and put them in a museum and we call those type specimens for new species. This is kind of the type section in the spot too that delineates the point of time between two intervals. So we talk about a golden spike going in at this point. Some spots literally actually have a piece of metal they put in the wall. You don't find that there, but that spot, if you want to visit it, you can. It's pretty close to us. This is a good idea to do this summer. If things go all right with coronavirus, go over to Newfoundland and you can go to the spot where you can see this thing right here. You can see that cool trace fossil and that represents literally defines the base of the Cambrian system itself. And it's right here. You can climb up in this hill and you can put your hand on that spot right there. And this is a thing called Treptignus pedum, or pedum maybe, Treptignus pedum. Pedum is foot, right? So it has to do with these. These hollow upward curving structures. So these are feeding traces, I believe. They could be locomotive traces. I think they're feeding traces going through the sediment and piercing through the sediment. So this is a much more complicated kind of path and they only get more complicated as you go beyond that. So here is a bunch of things that we call the small shellies. Why do we call them that? Because we were very clever. Because they are, as you see by the scale bar here, very small and they are also shelly. So some of these things, this thing here, for example, looks kind of like that looks like a snail shell. It probably isn't, but you can see it, something like that, right? Some of these other things, maybe this one here, I think that's something like a brachypod. The small shelly workers are gonna get angry at me if they're watching this video. But the vast majority of these things are not single shells of organisms. Rather they are pieces of things. So if you were to get a starfish to get and dissolve it, you ought to be left with a bunch of muck, not dissolve it, but let it decompose, a bunch of muck and a bunch of small little plates, little kind of calcareous plates that we call sclerites. And that's what most of these are. So these would have been tiny little pieces of armor, like plate armor on, or even scales is a good way of thinking. But think about scales and a dragon, right? These are little armored scales that would have been covering or spines that would have been sitting on top of more complicated animals. So these things represent, right? The expansion of what we saw with cladinia and nama colathus, which is an expansion of biomineralization amongst many different groups. So just like we've got a continual progress on terms of the complexity of trace fossils, we also have a continual progress in terms of the complexity and the number of organisms that are biomineralizing. So here's some more examples right there, right? More cool small shellies, lots of them here. And this is an idea of what they might have been like. So there was a reconstruction drawn apparently by someone's child. Actually, it's pretty good. My kid could draw that, I'd be really impressed, right? So this is some kind of organism, maybe this is like a velvet worm kind of thing here. And these are interpreted to have sat in his back. You can actually, you can see the legs here. You can see the legs. So in this case, we've got the small shellies preserved very rarely with a soft-bodied organism. Most of it's still soft-bodied, but it had some of these plates on the outside protecting it. So here are these sclerites, right? On a Cambrian worm with quotation marks, not really a worm here. So we go from these things at the base of the Cambrian and these slightly more complicated trace fossils at the base of the Cambrian. And by the time we get to the middle Cambrian, we got this stuff. So this is a, this is a trilobite. I mean, this is a fully complicated arthropod. They had eyes that were, you know, capable of actually resolving very fine details, amazing bits of architecture. You also have mollusks for sure, right? You've already got, these things show up. They're the kind of last big part of the Cambrian assembly. It shows up at 520. Prior to that, we had mollusks. So things like clams, right? That group, coral, sponges, the kind of things. These are all showing up before 520. And here is a, this is a, this is a thing showing various different localities around the world where you get famous, famous collections of fossils. There's a bunch of shales. You can see it's actually quite late, right? Here's the Ordovician up here, right? It's at 5, oh, eight. Here's the Chenjieang biota at 515. And then 541-ish down here is where the base of the Cambrian is. So this stuff is pretty boring. It's small shalys all the way up. And then we start getting lots of stuff showing up. And they start looking really cool. Here they are in context. Here's the base of where various groups are showing up. Anyways, the bottom line is, yeah, we have an explosion of diversity, but that explosion has a fuse. And the fuse runs all the way from at least 600, probably back to 635 now, if that molecular evidence that, that geochemical evidence is correct for the base of, the earliest evidence of sponges. So in that case, you've got a fuse that's running, you know, anywhere. If you take, let's say we take the base here as being 540, a little bit past 540, you've got a fuse that's running almost 100 million years. So the explosion is not an explosion. The problem is it's still an explosion. It's just an explosion with a really long fuse. So when you look at a fuse burning, I mean, if you've got a stick of dynamite, here's your fuse. Yeah, it's true that that is fire, but it's also true that when this thing goes off, it is an order of magnitude. Maybe they are the same in that this is combustion and this is combustion. That's a stick of dynamite exploding, right? But they are quantitatively very different things. So you have to, if you were to say, oh yeah, there's no problem, right? There was no explosion. It's just a steady change. That's ignoring that pattern right there of diversification, right? That's still needs. This here needs an explanation. And I'm gonna argue in my last couple of minutes here that I've already given you that explanation. What is that explanation? Well, I've got a few minutes left. Let's run through it. Here is the explanation. There's stuff blowing up. Okay, so here is what you get afterwards and what has changed. Well, possibly some things have changed, like the amount of oxygen may have changed, the availability of dissolved mineral materials that could be used to mineralize, that might have changed. So broadly there are three kind of big arguments that go in here. So maybe some kind of major environmental changes, maybe some kind of ecological changes, the way that actual animals are interacting with each other. Maybe something actually happened on a genetic level, right? So this stuff is actually a little bit out of, I haven't really followed this stuff too much. I'm in this camp. I'm fully in team ecological camp with the help of some environmental change. So the environmental stuff is what I'm gonna talk about first and this is actually a colleague of mine, it's a fieldwork with Bob Gaines. He's an awesome guy, we have the chance to meet him. He is a sedimentologist and he was arguing, he argues in this paper here that you get this great unconformity near the base of the game region that represents a dramatic change in the amount of weathering that's taking place. So a dramatic change in the flux of not just nutrients coming in, but importantly dissolved material that mineralizing material organisms could pull out. So the claim here is that the amount, the building blocks, the mineralogical building blocks that would have allowed things to actually build skeletons kind of came into play due to this massive shift in weathering dynamics that took place at the base of the Cambrian. How convincing is this? I mean, reasonably convincing, but I'll tell you, I'm an ecological guy. There's some argument that oxygen might have really kicked in in a second, right? That might have gone on. Why might oxygen have been at control? Well, it might have been related to the stuff I'm gonna talk about in a second because just like if you try to run, you know, a, I don't know, some kind of super car, like one of those, like literally the super cars, I don't know, I'm not a car guy, but like these crazy cars that you see, the amount of fuel they burn through as opposed to like a little go cart. So if you wanna run something like Kimberella, who is zipping around like the simple mollusk, it requires relatively little oxygen to power it. On the other hand, if you wanna power a predator, which is moving fast and trying to catch things, it requires functionally a lot more fuel in the sense of oxygen, how much it needs to breathe to run that. So the amount of oxygen you need to support a sponge is a completely different thing, like orders of magnitude off of what you need to be able to support, or at least unorder of magnitude off, we need to be able to support something that's zipping around catching things. So it may have been that oxygen was still a limiting factor in life, even through the ideocrine. And then you needed sufficient life to be able to actually get cool animals that are zipping around and eating things. That might be, that might be in effect as well. So all of this stuff, these are not mutually exclusive hypothesis. These could all be working together. So it could be an ecological trivr, sure. But it's certainly, and I say this with 100% confidence, there is absolutely a biological and ecological component. And we're gonna just end off the talk with this. These are a couple of big ideas I want you to think about. So what have we done at this point? Well, we've built mussels. I showed you the very earliest mussels going back in the, that stock jellyfish-like organism from mistaken point. We get eyes that start showing up. I don't know if we have anything with eyes actually in the ideocrine. We certainly get them in the Cambrian. We get teeth that I put quotation marks around. Because things like this, they're not strictly teeth, but they do the same things. They are shearing devices that are used for consumption. Shells start showing up. Remember, we get biomineralization of the very latest ideocrine. And then it explodes in the Cambrian, driving it. So all of this allows you to live in different ways. So if you are oranguomorph, all you can do is lie there. And that's fine, because you don't need to do anything else. But if you learn the trick of crawling around, then suddenly you can move to an area where there is more food. So food runs out in one area. You don't just die. You're able to move around. And that means you can live in environments where there are fleeting inputs of food or where there is less food or where there is periodic food. You can just move around and go to it. Once you've got muscles, you can move around. Maybe you're walking by oranguomorph and you go, that looks good. And then you learn the trick of eating the guy next to you. And if you do that, that now is a whole new way of making a living. If you learn the trick of predation, that's a whole new way of making it. Or maybe you don't predate. Maybe you just bore in and you steal the minerals. That happens all the time. You can find, if you pick up a big shell somewhere, it's probably full of little holes. But that's organisms stealing the calcium carbonate from that shell. That's an easier way of doing it. So if something is trying to eat you, if you have a shell, you're gonna be relatively protected. And if you have a shell, right, that means that you are living in a different way. And it's also gonna drive the guy who's gonna try to eat you to try to eat you in a different way, which is gonna drive specialization in your shell. So the very fact, these things are all allowing different ways of life, which is necessarily going to lead to more diversification, absolutely. But it's also simultaneously creating niches. You're now the predator as opposed to being the prey. Or maybe you're the thing that swims away when something tries to eat you. Or maybe you're the thing that swims after that thing. Maybe you're the thing that swims up in the water as opposed to the thing that crawls along the ground. Before you had no choice, you just laid there. But now that you can move around, you can live in different ways. And so this dramatic increase in the ways of living, supports the possible ways of living, supports a dramatic increase in the possible number of species. So you can see in this case, even without changing the actual physical environment, just by changing the biological capabilities of things, you're changing the environments that can be exploited. But simultaneously by doing that, you're creating new niches around you by forcing changes in other organisms around you. So here is an example. This is a really cool paper from 2014. You can follow this link right here when life got smart, good title too. This is, these are trace fossils from the upper Edeachryan, where you first get them going through, going through the Cambrian. And you can see they're divided into categories. This is microbial grazing. This is like a snail cruising along, eating stuff. Deposit feeding, that means actually getting in and like a worm burrowing through the sediment eating it. This is deposit feeding in a predatory way. So you're going after the things that are in the ground eating this stuff. This is suspension feeding, grabbing little things that are in the water, getting them out, et cetera. These are arthropods. So these are clearly things that are in the arthropoda moving along. And you can see that we have an increase in complexity. These are more complex stuff. So let's say the microbial grazers. So here it's just moving along, going in one direction horizontal. Now we're cruising along, moving along. This is convoluted, right? 2D avoidance. That means something's trying to get you or you run into an obstacle and you move around it. 3D avoidance means you actually cruise away from about burrowing underground, right? Directed crossings, pseudo spirals. These are all more complicated structures you have that represent more complicated behaviors. All right, so what is going on? This is the big transition, right? So here is the beginning, the simplest things. You're just swiggling along. These are just things moving along the surface. You go from that to things where it's like, I come along and then you run away. Like, wah! You run the other direction, right? Because you encountered potentially a predator, right? Then you get, you're cruising along and then what happens? You go underground and you escape this way and then come back up to the surface. This is a three-dimensional escape path, right? Getting more and more complicated. Eventually, the same thing with the feeding. The feeding behaviors get more complicated as we start to interact with the ground and start to take what's there in more complicated ways. And this is continuing all the way through the Cambrian. It just gets more and more complicated. This is another big idea I want you to think about. This idea of an evolutionary arms race. So you guys know the story of the Cold War. Let's say this is Russia and this is the USSR and this is America. So if I've got nukes, you need a bigger nuke to ensure that I'm not gonna fire them at you. I want a mutually assured destruction. They call it a mad. We want to both ensure that we're gonna have total superiority and mutual superiority. So if this guy has a club, this guy gets a gun, right? Well, if the bad guy's got a gun, I'm gonna get a better gun, right? Uh-oh, now the bad guy's got a machine gun, right? I got a better gun. The bad guy gets a machine gun, right? I get an even better machine gun. I got body armor and he shows up with a bazooka. So if you imagine this is a clam, if you learn you get really simple teeth, and this is not a clam, this starts off as a little, just has a few little sclerites in the outside, right? Well, then he responds by building a full shell. And now you respond by having a mineralized radula that can drill through it. And you put spikes all over your shells and then you respond by getting a better drill and et cetera, et cetera. So not only is this drive specialization each one of these, right? They're gonna change over time, but also as they get more specialized, right? You're necessarily increasing diversity, right? If you think about that evolutionary landscape we were talking about, you're making more and more and more very fine peaks. You're driving everyone off from standing on the bottom where everyone was off to these hyper-specialized peaks. So that's the idea of probably what's going on here is this is the advent of predation and it kills all these things that were just sitting there before. They can't live in a world like that. But simultaneously it's also, simultaneously it's also driving eventually more diversification. So you get this diversification of a different kind of thing, things that can live in this new nasty world. And that thing, right, starts interacting with the world physically as well. And this is the final idea I'm gonna leave you with, the final idea, and it's a big idea. Here is a thing called an archeosiath. These were the early, we don't really know what they were, they're sponges probably. These were the earliest things that built reefs. So if you go to a coral reef right now, it is a rock-like structure entirely built by an organism. And if you go there, you'll see there's things like clams and algae attaching themselves physically to it. So archeosiaths didn't build anything that impressive at all, but they built the simplest reef-like structures. So they would be sitting in the soft sediment and they would build a bunch of material that's hard out of their own bodies. That's now material that other things can rest on top of or walk on top of or attach themselves to. So by the very act of making themselves be a physical hard substrate, they've now created opportunities for other things to interact with them. There's now a niche of something that sits on top of them. And that didn't exist before they existed. So they have, in a sense, taken the ecosystem and changed it fundamentally in its characteristics. They have engineered it. They've changed it by their very presence. The biggest example though is right here. Is right here. So watch these little snails cruising along. See, there's a trail. That's the kind of very simple track we saw before. Look at them clean up all this algae. You see all this algae here? They're cleaning that all up. If you guys, anyone has an aquarium, these guys are really important if you want your aquarium to look cool. You need some snails in there, some suckerfish, something that specializes in eating up all of this algae. Otherwise it'll just cover up every surface, it'll be covered with it. The entire thing would just be covered in green. And it would choke out everything else. The algae would choke everything out if you didn't have this in there doing its thing. So think about that for a second and think about what a world would be like without anything that did this. Nothing that did this. No filter, no suckerfish, no clan, no snails, nothing that does this. It would be a world covered in slime. And just like it's covering every layer here, it would cover all of the sediment. And what it would do is it would take what is now a muddy environment and make it solid. It would essentially just have a film on top of it that you could walk around on top of. Or if you were a rangomorph, you could lay on top of. Now what happens when these things learn the trick of starting to eat that slime? And more importantly, what happens when things learn the trick of starting to now crawl into the sediment and churn it around? Just like if you get a shovel and start moving through the sediment and churn it around, right? If you get a bunch of hard packed dirt and start turning over the shovel, you're gonna make it very loose. When things start moving through the sediment, they're doing the same thing. So we started off with grazers, eating all of that slime that was kind of acting like a blanket on top of the sediment. And then we ended up with things moving in. And as they start moving in, and they start churning this up, they're allowing oxygen-rich water to come down here as well. Which means that now it's a place they can't just go in for a moment, they can live down here. Because now oxygen's been brought in by the very fact they've churned the sediment. This is a rock, by the way. This is a good example, just imagine it's sediment. Anyways, so they're very active doing that dramatically transformed the sediment itself. And this happened during the Cambrian. We call it the Cambrian substrate revolution. So you went from a world where all the mud was encased with a biofilm like this. And we've talked about this when we talked about stromatolites. Remember that stromatolites are just layers of cyanobacteria and other simple critters forming mats, bacterial mats. And they only exist today in hypersaline environments where nothing else can live. So in the past, the whole world was like this, not just stromatolites, but shallow water everywhere. It would have been covered in these films, which would have made the ground harden up for these things to live on. The moment things started cruising over top and sort of burrowing into it, it changed the nature of mud itself and killed this niche. And as more things started to bury deeper down and deeper down and deeper down, it transformed this even more and it brought oxygen down with it as well. It made this superior substrate. Here's things crawling down. So the age of the biofilms, that's the etiacrine, it dies in the end of the etiacrine. Biotrabation comes in and it's not only changing that, it's also by bringing oxygen down and bringing sediment back up and also things going down and eating this. They're changing how carbon is sequestered because before if you died here and got buried, you're just down there forever. You're covered in a layer of film, which is how we preserve probably these things like in the Burgess Shale. But later on when it's all being churned around like this, now suddenly carbon is being released back up so it's changed the carbon cycle as well. So this is this idea of ecosystem engineering and here's the link, I'll hover over it. This takes you to an ecological page, it tells you about it. There's the, if you wanna go there, you can also just check out the URL. And here's the steps going through from the etiacrine to the basal Cambrian and then through the Cambrian it starts to get more and more and more complicated. So the organisms themselves are changing themselves by their own interactions, but they're also changing the nature of sediment, what kinds of things you could have, the fact that oxygen is down here now. So this is happening, right? Grazers break down the biofilms, they expose the substrate, which allows them worms, things to go down and access the nutrients, all the dead things that are down there. They bring O2 with them, which allows things to go further, which brings more O2, which allows things to go further and on and on and on. At the same time, really simple little zooplankton learn to swim up in the atmosphere, in the water, and they're now eating things that are floating around up in the water. And when they eat them, they poo them out. And ordinarily what would happen is when a tiny little, like a little blue-green algae, a cyanobacteria died, it's so small it takes forever to fall down. It takes forever to fall down. So maybe that's it right there. And it's gonna take a long time to fall down and in this process, it's just gonna get decomposed by something else. But if you've got a bigger organism, which ate a bunch of them, the poo that comes out of it is gonna be that much bigger, which means it's gonna settle that much faster. Think about what we're talking about with settling rates for things like sediment. And so this is, these are feces coming down here, which means that all of this energy, which is bound up in this, right? This is food. I mean, this is gross food to think about, but it's food for something. We're transferring that from up here in the water column down here to the sediment. And it's bringing down, so we're bringing energy. This thing, these are little photosynthesizing things. They're gonna eat and buy things. So it's literally taking sunlight. It's taking solar energy in the form of little tiny microscopic plants and transferring that energy down to the deep water well below the photocone, where then things like clams and worms can eat it. So it's a whole scale transformation of energy, which allows things to live down here that otherwise couldn't. So that's this whole section here. So this interaction between organisms, they're substrate, organisms of each other is driving evolution. This is really, this is really what is key to understanding, at least from my perspective, but I'm a biology guy, right? What's driving this? So what is the fuse driving it? Well, probably oxygen played a role. Maybe weathering and the release of nutrients played a role, but almost certainly most of this explosion was driven by the fuse of organisms themselves. Muscles, eyes, teeth, shells. All right, so that takes us up to the Cambrian. From here, the world is now full of animals and we're on our march towards dinosaurs, which I promise you we will get to. So that's it. That went 15 minutes longer, which means the next one I'll try to make a tiny bit shorter. If there are any issues, please let me know. Okay.