 All right, are we ready to get started? Yeah. A nice trilobites there on the box. God, I'd love that. All right, so welcome to Science Circle panel discussion. I think this is our fourth presentation in this format of a panel discussion. So they've been a lot of fun. We did an event on the Fermi paradox about where are the aliens. And we also did a presentation about science fiction movies, which was a lot of fun. And I know there was another one, which I can't think of now. Today we're going to enjoy a nice substantive scientific discussion. Our topic today is the Cambrian Explosion. So this relates to the history of Earth and life on Earth. For, you know, about four billion years, life on Earth was really limited to single celled creatures and colonies of creatures. And as the chemistry of the Earth and the geology of the Earth changed, more complex forms of life began to appear about 541 million years ago. So the age of the Earth is about four and a half billion years ago. So we're talking about for 541 million years ago. So really pretty recent in the history of the Earth, but extremely ancient in the history of life. Very interesting things began to happen as revealed by the fossil record to life on Earth. And we have with us today to kind of walk us through this extremely interesting period to excellent panelists. To my immediate left, I guess, is Alex Hastings, who is an actual working scientist in this particular field, paleontology and geology. He is the fixed Patrick chair of paleontology at the Science Museum of Minnesota and an assistant curator of, or should say has been the assistant curator paleontology at the Virginia Museum of Natural History, and is a member of the Society of Vertebrate Paleontology and the Geological Society of America. And next to Alex is Day Miami. I think who is known to us here in the science circle. He's an educator at Franklin County High School in Virginia, a scientist research associate with the Virginia Museum of Natural History. His fields of expertise include paleontology and geology. He teaches earth science and also has a keen interest in virtual world learning and as the CEO of educational virtual worlds. So I think as you can see, we just have an outstanding panel here to for this topic. And with that, with those opening remarks, I would now like to turn the discussion over to Day Miami, who is going to help provide set a little bit of context for the camera. Take it away. Okay, thanks for again. I appreciate your comments and I greatly appreciate Alex Hastings coming back to join me on the panel. He started off with a fantastic discussion of tight town boa, and I'm hoping that he'll be able to come back and join us again. In the future, we were talking about how one of the things we might want to consider for science circle as a discussion of various museums and collections that are available. We talked about there's a nice collection at the Virginia Museum of Natural History, and maybe about the one that's in Minnesota. The other thing that we've been working on is, you know, there are two chairs up here. We originally planned to have three. And I was this past week, past two weeks, I've been trying to get shoe highs out from Virginia Tech State University here in Virginia to come join us. And he is, I consider him one of the experts on the planet on pre Cambrian Cambrian transitions. He's done some amazing research. He's done work in Beijing. He actually got his bachelor's from Beijing University and his, his PhD from Harvard. And he has joined Second Life and I think he has an interest in science circle as well. I sent him some information that Chantel gave me. He is at a conference this weekend. So I think he's trouble getting here. But a suggestion I would make is if we get you I am science circle to do a Cambrian explosion part two. And I'm sure she would give us a lot more information about this topic. So that said, I want to do is I talked with Alex this week by email and we tried to figure out how it would be the best way to organize it. One of the things that I suggested was, I would start with a little bit of an historical discussion about the Cambrian explosion. And all discussion of the development of the geology stratigraphy and paleontology. And then Alex is going to talk about the the Vendian which is the latest interval geologic time in the pre Cambrian. And some of the organisms then we've got some slides to show off. And then thought we would open it up to questions and maybe talk about some of the driving mechanisms, either at the spirit or environmental that may have led to the explosion of life. At the very beginning of the Cambrian. So, you can tell I saw things a little bit. I hope to get some slides at Alex's and it just didn't happen. So what I did was I threw out some primes in front of me. And let me see if I can make this full right there we go now you can see a little bit better. The box that I just turned on is a picture. And we've got today's voices a story and can he turn down his mic volume. All right, let me see if I can do that. I know where it is. It's in here. Whoops voice. Is that any better. So, so, I turned down my lines any better. Not really. Okay, how about that. So, I turned down any more. Or what I can do is I want a headset. Is that any better by swinging the mic away. We should have done a voice check probably too close to the mic day. All right, like I said, I've swung the. Maybe a little. So, I regret it's sort of congestion that I have. So, fortunately, I'm not going to be speaking. Okay, that's a little better. Okay, good. Like I said, I'm just going to make some opening comments and then and then Alex voice sound much clearer. Anyway, the box that just lit up is a picture of all and Ellis. And for many years, all and Ellis was considered the definition of the beginning of the founders of the age of life. Or the Cambrian and scientists when they found this fossil said, yeah, this is the beginning of it all. And if you think about it in the pre Cambrian, which goes from about 4.5 billion to somewhere around 54545. Let's talk about why there's a discrepancy. You have mainly just single celled algae and bacteria. There's some algal stream allies, but very simple organisms. And then up until about the 1940s, people said, hey, once you hit the Cambrian this 543 Mark, you get this explosion of organisms you get advanced trilobites with eyes and segmentation and so on. And there was a, there was a paper published back in 1972. In the New York Pallentological site notes entitled from whence came all these critters. And basically it brought up, you know, why was there this huge radiation of different organisms right at the Cambrian. And there have been a couple of theories that we can we can get into later. What's interesting, once you get into the 1960s, geologists started to examine the early Cambrian rocks and what they found is that all in Ellis is not the oldest fossil. Okay, that's been found. In fact, there were trilobites that were found below all in Ellis indicating that they were older trial bites than this thing. And when I worked at the museum, Virginia Museum of Natural History, I got a chance to examine some of these specimens. I'm going to turn this guy on next. This is an archaeo sciat that it's believed to be related to primitive sponges and so on. You find them scattered throughout they call this the small Shelley fauna that's below all in Ellis. And you get some really weird fossils. There's one called soltella that everybody has fun with. Because all this is these cone shaped fossils that you find association with archaeo sciat that's in and simple trial bites. And I don't think anybody knows what these are with these soltella cone shaped things are. Some people have suggested that some people have suggested that they were conularies which were related to jellyfish today. Perhaps they were mollusk and related to cephalopods. Some members of the USGS want to put them in a whole separate phylum. But nonetheless, it's interesting that there's been a lot of work done on the Cambrian. A lot of the problems that we had with the pre Cambrian Cambrian transition is that there just wasn't a lot of careful field work that was done. Until you start getting into I would say the late part of the 20th, 20th century early 21st century where a number of geologists started to meet and look at different ways of of establishing where we're going to put the boundary. So the fossils like I was just at Virginia Tech and Shuai said that the latest definition of the pre Cambrian Cambrian boundary, they've now put it at 543 million years old. And they're defining it on the base of a trace fossils, some simple burrows of this organism that. So what they put into the sediment is, is what they're using as the as the official definition of the Cambrian pre Cambrian boundary. That gives you a historical background as to, you know, 100 years as to what people considered the the fossils associated with this. Now we're going to do is Alex will talk a little bit about some of the more recent discoveries and the bendy and which is the latest geologic time period. Last one described but also the very end of the pre Cambrian. So I'm going to turn off my mic and I will let Alex take it from here. Actually, Alex, if you don't mind, I may I entered may interject a question before, before you begin. So, one of the things I'm curious with the archeosythe cones. Is it is what are were these animals mobile. One of the things that I think is interesting about the Cambrian was the increase in mobility of animals. So is it, is it thought that the archeosythe were stationary or did they have some ability to to move. My understanding is they were attached to the seafloor. If you look carefully at the pictures and the reconstruction, they have a simple root system. They just attached them. They're simple to feeders. In the column that allows word to go in and take out oxygen and food. And I think you want to talk about the mobility issue. Certainly organisms were mobile by the time they get to the Cambrian. Animals, they're not plants. Yes, that's right. They are animals. And one of the reasons mobility is interesting is because it is my understanding is it kind of leads to the advent of predators, which really put pressure on life forms to diversify and find new strategies. So with that, I'll turn it over to Alex. Thanks. And Bill maybe can help out with some moving the slides forward a bit and that should kind of help visualize things as we're going here. So I wanted to kind of give a little bit of the background even before this to kind of give you a sense of kind of what the world was leading into this. You know, several billion years history leading into it. So, Bill, do you mind moving the next slide forward? There we go. They're going way, way, way back to the beginning of earth, more or less when there's still kind of the crust itself is forming around there. There's no life whatsoever. For the first, you know, half billion ish years of earth's existence. That's been referred as the Haiti and after, of course, Hades and inhospitable landscape that lasted for quite some time as kind of things were starting to bill you can go ahead and go to the next slide. And then that launches us into the Archaean, which is a really long period of time in Earth's history, but that's when the first signs of life actually starts to come. That's kind of been some arguments exactly what that date is. It's typically a little bit younger than four billion years ago, but still very, very early in life's history and a lot of that is kind of bacteria or even simpler organism. But one of the things that really has been the best fossil evidence by far for this early period of life is fossil called a stromatolite, which is created from bacteria or cyanobacteria. And it's this kind of not technically an algae, but this kind of algae looking thing that would kind of crust over a layer and then they would kind of build up mud over time and they build up another layer on top of that and over and over again. It creates this kind of mushroom style. So we got a picture of a fossil in the bottom right there on the screen in these in cross section, you can kind of see these there's and they're really distinct from sediment around them, and they're kind of our best evidence of life from this time. Brazily, even though these things go back billions of years, there actually are places on earth where they're still alive. So the picture in the top there is from sharks Bay Australia, which is one of just a handful of places where these stromatolites can still be found. They can live in really range environments so they can tolerate very, very saline waters, where a lot of other things can't and that's typically where they still exist because there aren't any there's anything around to eat them because nothing else can live in that environment. So another place where you can find them are these hyper saline lakes in the Bahamas like on land itself, but they're very, very rare and only a few circumstances. Anyway, so they were photosynthesizing essentially. So they were able to basically work in this pre oxygen atmosphere. And since they're around for billions of years and had no had nothing eating them, they generated a lot of the oxygen that we have here today over this massive period. Bill, can you go to the next slide? And then that leads into the protozoic. Now the protozoic is a kind of large chunk of time that goes all the way up to the Cambrian that we're about to, there's the subject of this section here. And in that time you see even more high abundance of these oxygen creating bacteria. But for most of that time period, there's still really, really, really simple forms of life. One of the really great parts of this is actually right here in Minnesota. We have a lot of the banded iron formations, which is a picture on the left, which is this can be this really nice, beautiful red patterning. And that's where basically because now there's oxygen in the environment, iron actually will rest whereas before this it doesn't really because they're not exposed to oxygen. And you see these in these kind of stromatolite rich beds there. So it's another good indication of how we got the atmosphere that we have today. And that's largely due to life. But everything was really, really simple. You have basically just bacteria around and really about it for billions of years. And then basically when the Cambrian explosion came around life got really, really complex. And for a long time, that was thought to have been kind of the defining boundary of life and especially complex life. So the period starting at the Cambrian at 541 is the Phanerozoic. That's the time of life. And before that is this kind of ancient. It was thought that really wasn't much to complexity in life before this time. However, much more recently, there have been a lot of discoveries in what's been called the Vendian is also the Edian. Even before the Cambrian where you're starting to get fairly complex life. Now in this scenario, so we've got kind of reconstruction in the right there. They're not really plants. They're not kind of animalish. But they're this weird group or several groups of organisms that still had fairly large body size. So some of these got maybe a foot long. I think a couple got a little bit bigger than that most are a bit smaller. Where you have this kind of shallow marine ecosystem where you actually have things that are doing a little bit of. But it's synthesizing on a bigger scale. You also have things that are probably eating detritus. So things kind of floating in the water. Still nothing that's like eating each other. So you really don't have predators yet. So nowhere near the complexity of life that you see later on. But we're actually starting to flesh out this larger view of life and kind of building complexity over time. This is something that's really boomed a lot in just the last 20, which is relatively short from the grander. Oh right, I should be looking at our questions here. You do wonder when the mitochondria got captured by the cells like we have today. That is a great question in terms of like how Eukaryos developed. This would have been prior to this Ediacaren period, but that still only narrows it down to a billion years of time. There's not a lot of good solid kind of union on that. Another kind of parallel to that with mitochondria is also the actual ability to photosynthesize in plants. And there's a lot of those chloroplasts that are actually doing that action in this scenario there. Oh right, and this is someone mentioned, oh, there I got it right. Deeper water creatures couldn't photosynthesize stuff that got nutrient by osmosis. There's a lot of kind of alternative ways to get energy. In terms of things like these Ediacarans and a lot of these cyanobacteria, they're in fairly shallow waters that sunlight wouldn't have been a huge problem there, but together, exactly. So, and this seems to have been kind of where the most kind of boom of complexity of life came in in the Chalamarine. Let's see, Bill, do you mind going to the next slide? So the Cambrian represents the very beginning of that Phanerozoic. So it's kind of still has the name stick around of being kind of the time of life. And the Cambrian itself ran for what is that about six years and million years. And in this kind of relatively narrow packet of time we go from still fairly simple forms of life. Like the Ediacaran fauna to really, really complex scenarios where you have that full ecosystem is fleshing out with small predators. You got scavengers, you have larger predators, at least for the environment there. And you get this really, really cool experimentation period of life where you actually established several main groups of organisms all within a relatively short time period. But they're doing a lot of fun and interesting, and at least by our modern perspective, weird things all at once, all very, very rapidly. Can you go to the next one, Bill? All right, so this might be a little bit hard to read, but basically this is just kind of an evolutionary tree showing this time here. So basically in the light green you've got kind of the time of the Cambrian and what you got are kind of several major evolutionary lines popping in more or less as soon as that boundary happens. So you're getting things like sponges and arthropods and mollusks, broadly speaking. Trinoderms, all these really, really critical groups to modern ecosystems that you really didn't have before that. And then from there they start expanding and rating into many other groups there. This figure also calls out one really, really significant geologic formation, the Burgess Shale, which is that white line there. You'll see there's a bunch of little yellow dots there. Those are keys in where kind of more radiations are happening within the time period. Now this is a rock formation exposed in Western Canada where they just had really, really phenomenal fossilization there. Where you're getting soft tissue preservation of these delicate little creatures, but across the entire ecosystem. Getting all the weird and cool things all together in one scenario. You can really flesh out what the... Can you go to the next one, Bill? So to kind of set the scenario there for what the world would have looked like, it's pretty heavily flooded a lot. So you have the massive panthalatic ocean occupying a large part of the world as well as the Iapetus. You've got a large... This is all pre-Pangae I should add. You've got massive land mass kind of over on the eastern part of the hemisphere. If you're looking at North America, that's more or less the thing in the middle here. And what you'll notice is there's an outline that's got shallow seas around a land mass there. And that's basically where we're finding a lot of really great Cambrian fossil sites in those shallow seas around the ancient continent. Much smaller North America that existed back. So the Burgess Shale is kind of very much in that area. And interestingly, if you want to find other really good Cambrian fossil sites, you often kind of flip around over to like Nova Scotia in eastern Canada. Part of the reason why Canada has a really good fossil record this far back is that the Canadian Shield is kind of the basic kind of nucleus to the North American continent. So it has the oldest land mass and therefore it's got the oldest potential for these deposits to build. So Canada has a bit of a priority on really great Cambrian fossils especially compared. Can you go to next? And then we'll try and catch up on some of the questions. Let's see, there used to be a lot more oxygen in the atmosphere which allowed the dinosaurs to get so big it's theorized that after the flood. Ooh, there's the atmosphere where it didn't freeze like so much there. Let's say I'll just broadly talk about oxygen. So there have been times certainly when oxygen has kind of increased and decreased. And this is thought to have kind of helped out particularly certain kinds of groups to be more productive. Oxygen tends to favor things that absorb oxygen in different ways as well. So one of the heydays is actually after the Cambrian you've got the carboniferous period which is basically when you get most of the carbon in the coal deposits built up. And in that time you see arthropods so like centipedes and millipedes and really, really large spiders, things that were able to get much, much bigger and greater abundance because of the higher oxygen. The way they absorb oxygen is through their exoskeleton. So there's actually a limit on how big they can get based on the concentration of oxygen in the atmosphere that does translate to water as well. And that may have played a role into this, but I don't know that it's all that well understood as far as kind of something as specific as oxygen level. So this slide here is just kind of highlighting a couple of the iconic animals from the Cambrian period. The top left one there is anomalocaris. That was a predator. You can actually see next to that you've got a human being there and you've got anomalocaris next to the smaller part there. It's a good size. I think it was the largest predator of its day. It's in this kind of really weird obscure group and it had these two prehensile appendages coming off its face there that would have actually been used to grab things like trilobites, bring that up to the mouth and be able to crunch it down. There is a few different kinds there and they seem to have been sort of the quote lions. Another fun oddball is opopenia below that and has a little bit of a similar body plan except that instead of having these two kind of prehensile organs on its front, it has this kind of long proboscis where it has this kind of sort of teeth like projections at the end of a trunk. And that would have been flexible and able to kind of grab stuff so it could have rooted around in sediment, kind of pick up small creatures and eating them directly. And neither one of these really has any close relatives alive today. One of the other fun ones is hallucinogenia up in the top right. This one is kind of a, it's essentially a worm, but had these big long projections off of it and for the longest time they did not have a head. It wasn't until just a few years ago that they finally found one with the head curved and it's this weird kind of like almost cartoonish, just like two little dots there with a mouth and it's kind of a, it looks very docile in a way. It's kind of interesting. But this is essentially such a weird group that has kind of its own line of worm evolution. It's not really getting through segmentations and makes them. And the last one I wanted to call out here was Pacaia. Pacaia is particularly important because it is a very, very early relative of vertebrates. So in a lot of ways, this is our great, great, great, great, great, great, great ancestor going all the way back to this early boom in life at the Cambrian. And this is very, very simple in that you're basically getting the same kinds of segmentations, like an early form of the spinal column. A lot of times this kind of gets folded into the larger grouping for data that we belong to. But before you get to true vertebrates and certainly before you get it to anything having true bones. But that important style of segmentation that we now have in our own backs really has its basis way, way, way, way, way back to this fossil sites in Canada. And there have been a few other kinds of relatives these found in a few other places in the world. So I'd say there's a bunch of stuff here I'm going to try and catch up on some of this. Alex, can I jump in a little bit on the oxygen question that go back? Yes, go for it. What I think is really crucial that people understand is the Earth's atmosphere was pretty much devoid of oxygen when it formed, and that was a good thing. Are people familiar with the Miller Urey experiments that were done in the 50s? Oh, of course, yeah. Miller Urey were two scientists at my alma mater at the University of Chicago. That's why I keep bringing them up about how they had this large glass container and they put pre-cambrian gases like methane, sulfur, ammonia and so on in there. And they ran electric current through them with water and they got some simple organic compounds out of them. And the argument that if there had been oxygen around when these first organic compounds came into the oceans, they would have just been blown to pieces since oxygen is so reactive. So it's probably a good thing that there wasn't much oxygen around. And then through photosynthesis of algae, stromalites and so on, we progressively go towards an oxygen-rich environment. And you didn't talk much about the Vendian organisms. They've been found in Mexico, Russia, Southern Australia. And just fill that out a little bit. Some really bizarre things. In fact, in many cases, we don't have modern analogs to even compare them with. They give them terms like the bilateral, meaning that they have bilateral symmetry or the radiata. Maybe they were like jellyfish or worms. We really don't know because they're so soft-bodied. But there are definitely some kind of weird transition that's going on between very simple cell bacteria and more complex life. The story is I am and me about a question about that I threw into General Tread about whether mitochondrial or DNA could have come from Mars. And it's a little pan-spermia theory. Do you want to say anything about it? I'm a little skeptical about that. About pan-spermia? Yeah, about that. How do you feel about that? Just to give you guys the background on pan-spermia, and you kind of already hinted at this bill. Basically, you've got the idea that life did not actually originate on Earth. It originated elsewhere and basically found its way through space rock, essentially, onto Earth. And then that sparked life here on Earth. It's a really neat idea. It's going to be very difficult to prove anything like that because we're going so far back in time. And really what you would need is something like if there was life on Mars that then sparked life on Earth. Hypothetically, if you could find life on Mars, then you could look at what the levels of similarity between the two are. And if they're highly similar, then that would be a good support for that idea. It still doesn't get you to proof. So it's a cool idea. I don't know that it's necessary or that you'll really be able to definitively show that in my lifetime, anyway. Alex, this is Berrigan. Just to interject, maybe a fun little thing about pan-spermia. At one time, Francis Crick, one of the co-discoverers of DNA, was an advocate of pan-spermia. His reason was the abundance of molybdenum in biological processes on Earth. Sort of a disproportionate requirement for molybdenum compared to its abundance on Earth's rocks and so forth. And so he thought, well, maybe life evolved on a planet that was rich in molybdenum and came here. So just thought I would toss that out as that there is a high-profile scientist who, at least one time, was interested in the pan-spermia idea. Yeah. I mean, the whole kind of tiny subfield of astrobiology is a really fascinating one. And a lot of it ends up stemming from the ideas behind how life would originate. I mean, it had to have started somewhere at some point under some circumstances. So even if you're looking at life originating here or life originating on other planets, how exactly do you do that? And that's where kind of the original puree stuff, how that would physically have happened. But it's definitely an area that has a lot of room to grow on. There's a lot that we don't yet understand how exactly life itself got. Let's see. So I'm finding all kinds of cool comments. A little pre-word. Cool. Mino essence. We're talking early life. I'm trying to catch up. Ah, so there's one comment here on life on Europa. So this is one of those where I think we, you know, whenever we are able to send something to land on Europa and actually starts looking into details. So places like that might actually be really good circumstances for finding life on other places. And see, the big contenders are Europa, Titan, and possibly Mars out there. I do know that they have included a lot of equipment that was designed to detect signs of life on Mars. None of them came definitively to any conclusions on that. And there was enough pushback because they didn't get very solid results on anything that, you know, instead maybe we should try and get when information were a little more likely to find. So kind of the larger pushes that the Mars work has been on different geological factors. And anyway, so there's, there's other cool things to learn about Mars. So that's been kind of a little bit of a pushback on the search for life on Mars specifically. So this is Baragon again, just to kind of refocus us on the Cambrian. One of the things, one of the things that interests me about it is the emergence of predators. It seems to me that the change that the emergence of predators created kind of an arms race where the prey had to adapt to predators. But this was a tremendous engine in the explosion of diversity in the Cambrian. And I kind of like to get both of your thoughts on that. Yeah, so absolutely. So this is part of also kind of why I brought in things like anomalocaris here. So when you're looking at that Edia Karen, Vanna, the one that I was talking about before, you have it's fairly simplistic and you don't have a large. You don't have nearly the complexity of an ecosystem that you see in the Cambrian. And having predators really, really increases your natural selection enormously. So you start seeing all these fun adaptations, not only in predators, but also in these prey forms. You start seeing things like trilobites that have this kind of thickened exoskeletons that are a little bit more armored. You see stuff like this hallucinogenia here that's got kind of these large spikes here. So it's kind of helping avoid sort of predation. And you start seeing things kind of taking on different modes of life entirely. So things are actually free moving and they're not nearly a sessile. So things that are able to move actively in with purpose that you don't really see prior to this. So you have this kind of potential thing that's maybe like a little bit of a jellyfish, but jellyfish are mostly just kind of reactive and a little bit more passively moving around where something like the anomalocaris there on the top left is actively seeking out things. The other interesting thing that that does is then it creates not only this new natural selection of pressure in order to help drive evolution and help kind of push things into new directions, but it also starts bringing in intelligence in a way. So you start seeing things that have to start to think a bit about the environment that they're living in. And so something like a predator has to be able to find stuff. There's at least some kind of function that's happening there that you don't really see prior to this. And that shows up in prey as well that has to avoid predators. So as you're saying that predator really is a major, just the fact that there are predators as a major evolutionary drive that really got kick started in the Cambrian. And basically as soon as that happens, geologically speaking, you have this giant, giant boom in Percy and then you end up establishing a lot of major evolutionary lines that then become successful enough to have modern relatives that are large parts of the ecosystem. And a lot of that is thanks to the dawn of predators. Bill, did you want to add anything? Yeah, we already talked a little about the role of oxygen and how certainly by the beginning of the Cambrian, we have an oxygen-rich environment which is going to support more advanced life like you're seeing on the slides. Another thing that recently has been discussed that was very important was the snowball earth theory as a way of driving the diversification. Paul Hoffman at Harvard has argued that towards the end of the pre-Cambrian about a billion years ago the whole planet froze over and life was hanging on by a threat. You had very simple organisms that were huddled around hydrothermal vents trying to stay cool, I mean just trying to stay warm. And it wasn't until the planet pulled out from this snowball period that advanced mental life could expand. But I think there's a number of things that we can point to and look at as to why you got more complicated life occurring. And we're still researching it even here in Virginia. The Department of Mines, Murals and Energy, David Spears who's the director of that has asked me, so do we have any pre-Cambrian fossils in Virginia? We don't even know the answer to a basic question like that. We know they're in North Carolina because we found them. I've tried looking in some of the late pre-Cambrian slates around the Virgilina district in the south part of Virginia and haven't found anything because you get into metamorphic rocks. But there's still a lot of basic field work that still needs to be done to answer these questions. We've been making progress but we certainly need more of it. There's a lot of slate in the Virgilina district to look through to see if there's anything there. One of the factors that I've heard about for the Cambrian explosion was as we were transitioning, as the earth was transitioning out of the snowball earth phase and the glaciers began to melt and exposing the rock underneath them that had been trapped by the glaciers. This resulted in lots of erosion which added lots of minerals and nutrients back into the water. So maybe in combination with the oxygen, this new abundance of minerals and nutrients added to the seas as the glaciers melted also contributed to the explosion of life. Well said. That's good. Yeah, I mean there's definitely a consistent tie with climatic shifts particularly when you're going into kind of warming phases. You typically do see higher amounts of diversity at least on kind of geologic time scales. And certainly something like snowball earth, a scenario where you have a very, very cold earth for a very long period of time would have acted counter to something like the Cambrian explosion would not have occurred in that same. So Bill, I think I had at least one more slide. Do you mind going? I think there's one more, right? Yeah. Oh, so this is just kind of more specifically about the Burgess Shale. Oh yeah, we should talk about the Burgess Shale. I'm just going to say, yes, we can't have a discussion of the Cambrian without discussing the Burgess Shale. So I'm glad you brought that up. Yeah, absolutely. So it's just what we would call a Lagerstette, which is actually a German term that's now been kind of incorporated into all of paleontology. Basically, it just means it's a site of incredible preservation. It's from the Middle Cambrian, so it's not quite at the beginning. So it's about 508 million years ago. And because this unit just preserves such immaculate details like this is an early form of worm here that just has this beautiful kind of feathery tendrils off of it. All of it amazingly preserved. Getting these soft tissue organisms from so long ago is just absolutely incredible. So this is a world-class site. I'm pretty sure it actually, no, it's established as a UNESCO World Heritage Site now just because it is so critically important to our understanding of the history of life. So it's one of those that's on my bucket list I hope to get to sometime. It's in a little bit out there. So it's on kind of the eastern side of British Columbia in western. And Bill, was that the last one? I think that might have been the last line. Yep, that's the end of it. Okay. Bill, I just want to make sure I hit everything. The Burgess Shale was the discovery of the Burgess Shale and the antiquity of the fossils, outstanding preservation, and the diversity of life forms found in the Burgess Shale was really the first, that's when sort of my understanding is that that's really when the, how spectacular the Cameron Explosion was really hit people. Like, you know, holy moly, look at all of this amazing life that just, you know, all coming out at the right around the same time. Absolutely. And the previous slide that had Enamelicaris and even the early pre-vertebrate came from specifically the Burgess Shale and some of these have only been recognized at this one place because fossil sites, Cameron fossil sites aren't common and especially Cameron sites that preserve soft tissue like this are very, very, very rare. So a lot of what we know about that Cameron Explosion comes specifically from this one place. And it's, as you say, it kind of really helps visualize the amazingness of what they've got there. And there's a group that's working towards kind of visualizing these often bizarre looking animals there so you can kind of get a greater appreciation for what life was like at this time. So I'm looking through for questions. So one point, I think, Berrigan, you mentioned eyes more or less come in at the Cambrian as well. And this likely also kind of ties into your predation scenario, but maybe not exclusively. So if you're imagining something that has to one has to find something, having eyeballs is a really good way of finding them, right? Even for prey or for things that are not predators, having eyes then becomes a really great way of realizing that you've got something you need to get away from, right? That's helping drive another aspect of evolution. And now eyes, of course, are a fundamental part of most ecosystems where it ends up being very dependent on kind of visual cues are critically important to all kinds of forms of life and fantasy now. A lot of things to innovations that happened during the Cambrian. Yeah. I don't know if there still is, but didn't there at one time, wasn't there sort of a subspecialty in paleontology of fascination with trilobite eyes because they were advanced and complex and each species had its own sort of different type of eye and so forth? Yeah, there is. I don't know that it's necessarily stopped, but yeah, the compound eyes of trilobites are particularly advanced, especially for the time in which they came around. And then you get these really weird forms too where you've got like stocks where the eyes are actually kind of extended out and the idea is that these things were kind of going into the subsurface a bit, but they still need to be able to see things that are going on above. So they have these kind of eyes that on tubes more or less, they could be a little bit safer under the sediment but still be able to see. And there's a whole host of complications genetically that go into forming something. Yeah. And even though you're still looking at a few millions of years for a lot of these things to be popping in during the Cambrian geologically speaking, that's very, very soon. And the fact that you have a lot of these things happening more or less in tandem, just showing that these massive, or massive, yeah, overturn in life and evolution, making the major radiations across this shell marine ecosystem that end up having very, very firm, establishing very, very firm roots for the rest of life. To me, it suggests that even though it seemed that life was relatively static for a long time, sort of underneath the surface, the DNA and our cellular structures were quietly sort of assembling the building blocks for these complex structures to be able to emerge once circumstances were right for them to. And so that, well, one other thought is that all these creatures live in the water. And so, and the development of ice requires light. So are these creatures essentially sort of shallow water creatures that where the light can still penetrate in, you know, deep enough into the water. So in terms of like the Burgess Shale in particular, this is a shallow marine environment where light would have been pretty, it would have been fairly well lit during the day. So you're looking at something where light is having a bound impact on kind of that evolutionary drive. So especially when you're looking at things, but it's also kind of helping form the basic bounding blocks of kind of more photosensitive sizing organisms that are kind of forming that baseline for the ecosystem. And then it kind of scales up to all the way up to predators. So it seems like the, at least in terms of complexity of life, really came in in these light rich marine environments, which is also consistent with the Precambrian, like the Vendian, the rangeomorphs, the early forms of life. So like the Ediacaran fauna, which is one of the best representatives of that is this shallow marine ecosystem from Australia. Even though you've got forms of life kind of from hydrothermal events, that real boom in complexity of life seems to have come in in the shallow marine environment where light was a major factor. So yes, let's talk a little bit about the Ediacaran and the Vendian, sort of the sort of late Precambrian because I think recent discoveries there have shown that maybe the transition to the Cambrian complex animals may not have been as abrupt as originally thought and that there was a population of sort of a little more complex animals prior to the Cambrian explosion. So let's explore that a little bit. It's, I mean, so the idea is that... Excuse me. And the reason I want to jump in on this was because I worked with Jack Sapkowski in Chicago. He was my evaluator. And one of the things that Jack impressed upon me was how crude our understanding of the Cambrian Precambrian boundary was back in the 70s and 80s. I remember as a high school student trying to memorize the geologic timescale, it was so frustrating because they would put the boundary at 600 million years ago that it was 575 million years ago, that it was 545 million years ago, that was 543 million years ago. And I asked Jack about who had done his PhD work on the Cambrian of Canada. And he said, it's just so hard to get good, hard data on the Cambrian, Precambrian boundary. And they're trying to look at a number of different ways of defining the boundary. Like I said, originally it was defined on the first occurrence of Olin Ellis. Everybody agreed that wasn't going to work. So they tried to look at other ways. They looked at isotope ways of defining it, trace fossil ways. Like I said, it took 20, 30 years before we even got, or even close to a consensus of opinion as to where the boundary should be. And like the comment I just made, I think there's more work to be done. I've talked with some of the geologists down in North Carolina that came to visit to the Virginia Museum of Natural History. I told them about what I had found in Virginia. And they said, oh, you're too high in the section. You've got to go lower. You've got to find somewhat older rocks. And then they mentioned to me that some of the, some of this quote, Precambrian fossils that they found were integrated with trilobites, which tells me some of the things from North Carolina aren't even Precambrian. They're Cambrian, but you've got trilobites in them. So there's some serious field work that still, I think, still needs to be done to get the resolution we need to really understand what's going on at this crucial boundary in Earth's history. Agreed. And, you know, it's not an easy scenario to work in because, you know, there are Precambrian outcrops, especially like fossiliferous ones, really aren't that common. And particularly ones are going to have preservation good enough where you're getting a good idea of what an ecosystem is like are even rarer still. So there are opportunities out there, but it's not going to be a simple or easy kind of thing. It would require a good kind of field-intensive area of study to kind of get into this more. There are people who are kind of focusing in on this really fascinating period of life, but as you say, there's quite a bit of room to learn new things about it. I think one of the interesting things about this sort of a late Precambrian is that even though it appears that we have found, you know, fossils of actual animals in the Precambrian, that is, you know, they're not plants and they're not microorganism colonies. They're something else. They're not photosynthesizing. So they must be sort of eating in some way. But I think what's healthy to appreciate is that from the fossil record, it seems like there are relatively few types of animals, maybe a half a dozen types of animals, much, much fewer than we see in the Precambrian. And it's also unclear whether or which ones of them might have left descendants. It appears that really most of the few types of animals we know not leave any descendants. So in terms of kind of the types that we see in the Cambrian, we do see a lot of these things like arthropods that are really establishing themselves around this time. And then they obviously have a very, very profound all the way through the system. There is a little bit of kind of experimentation area where you're getting these kinds of groups that even though they were pervasive for a while, they did not make it through later mass extinctions, they end up with kind of odd balls that don't really have modern relatives. And you got this opening up of opportunities where life is kind of trying out different things in a while. And you see this kind of scenario a couple other times in history. It's often after mass extinction event or major climate climatic events. So I'm thinking particularly like after the Unpermian extinction, which is kind of the biggest of all extinctions, after that time you see these kind of early forms of particularly what would eventually give rise to things like crocodiles and dinosaurs, but you also get a whole host of other kinds of animals in that vein trying out different scenarios and not all of them. So especially when you're kind of getting into a new era of life, you tend to see a lot of different forms coming in and then climb a lot of those die out and end up with a scenario that's distinct, very distinct from the earlier forms after those major evolutionary shifts, which are typically driven by major changes in climates like mass extinction. All right, very good. I'm sorry to say it looks like we have run out of time. It's already past the hour. So I guess we'll have to wrap it up. I'm sure we can keep talking. Let's see. Perhaps maybe if there are any group announcements for Science Circle that Chantal would like to maybe post that. But otherwise, I would like to thank our panelists, Alex and Dave, for really providing us with fantastic expertise about this fascinating topic in life. Thank you. We'll give them a round of applause. And with that, I will bring this session to a close. Thanks again and good night, everyone. Thanks.