The Cambrian Explosion and the evolutionary origin of animals with Professor Paul Smith

Welcome everyone and what I want to talk about tonight is the

origin

of

animals

, this event that we call the Cambrian

explosion

and really look at what we mean by that and then focus on one particular locality that, as Jack says, um , I. I've spent quite a bit of time looking at it as part of my research in Greenland, so you'll be familiar with these references to the first animal exhibition which, sadly, is now behind closed doors at Oxford's natural history museum, but luckily all is well . available online and if you want to explore the fossils that I'm going to talk about and the environments that I'm going to talk about in a little more detail, then go and take a look at that website where it has most of the exhibit. uh content and I'll repeat that URL at the end of the conference so what we're going to talk about tonight is not a new question.

I do not claim that it was, in fact, one that Darwin identified when he published On the Origin. of Species in 1859 in November 1859, just six months before the museum in Oxford opened, he recognized a real difficulty that the fossil record posed with his new theory of evolution by natural selection and that is that, as he said, there are Another allied difficulty that is much more serious, I alluded to the way in which a number of species of the same group suddenly appear in the lowest known phospholitic rocks, so what I was trying to say by that was that strangely there must be some Evolution that missing in the Rock record if Multiple numbers of species from the same group appear at the same time rather than being spaced out over time and across the rock record, so it was a problem that Darwin was never able to solve during his lifetime and within and out of its Sciences busy since 1859, but with a real acceleration in the last few decades and a lot of research effort has been put into this question like the Origin of Species and really only in the last couple of years I think we started to make some real progress in understanding what the questions are and what the different answers to those different questions are, so if we think about a modern marine ecosystem, if we think about a place on the planet with great animal diversity, we might think about something like This, a modern crown with many different species of fish, very visibly vertebrate

animals

, the groups to which we belong, but also corals and lurking in those crevices and crypts, many other species that represent different groups of animals, but if we We go back before the Cambrian, it is very different for the first one.

Three billion years into Earth's history, a photograph equivalent to that would have looked like this. It's a microbial film that grows on a sediment surface and you may be able to see that there are little pustules, these little bumps that are visible and that's where the decay gases are found. of the older mats as they rot are pushing against the bottom surface of the map which is methane, uh bubbling up, but there are other bubbles as well, one here and that is an oxygen bubble that is released through photosynthesis, so These are photosynthesizing microbial masks created by cyanobacteria. or blue-green algae, as we used to call them, and they're forming these films as storms hit that surface, tearing off flakes of sediment and transporting them, so they start to become rockets that start to semilithify, certainly consolidate in such a way that it can be reworked by current action and that was all marine ecosystems were for the better part of three billion years until animals came along and changed things really radically and now these kinds of microbial systems are not very common, are present in only a few places around the world, you might wonder how we get a photograph of a Pre

cambrian

ecosystem.

This is actually a puddle in the Lake District of England, a long-standing puddle that doesn't dry out and just dries up. to mimic those environments so we can understand the processes that happen, yes, but if we go to the Rock log and take a look at what the rocks tell us, we have similar characteristics, so now they are pre-camp rocks. the east coast of Greenland about 74 degrees north on an island called Ella and these are microbial films this time they have actually grown into a reef so we can get quite complex structures developed from microbes and bacteria and if we are getting close to that.

The stick is one meter long. The yellow stick, if we get closer, we can see that in detail what we have is a series of columns of these bacteria that compete with each other and like films and grow towards the sunlight to capture the greatest amount of sunlight. as much as possible for their photosynthesis, so this is typical of rocks from about 800 million years ago and if we zoom out from that scene, what we have here is a fairly complete succession from 800 million years ago to about 450 million years ago of years. what we would call the hearing, so we pass through the late Pre

cambrian

into the Cambrian and those distant hills here are the lower part of the Mineral Division and its tropical limestones almost as far as the eye can see, except for this Cliff here and this Cliff Here and in those two Cliffs something very different happens that is really significant for our history because in those Cliffs we have rocks like these that do not look very Limestone, in reality they are Tilites, they are glacial deposits and the red blocks that you can see are granites, the Gray blocks are limestone, slightly yellowish blocks are sandstone, they have all been picked up by glaciers and deposited, so what we are seeing here is a major glacial event similar to the previous one. that happened in the northern hemisphere until 10,000 years ago, but if we map these localities, they are absolutely global and it is an event that we call, as it says there, Snowball Earth and reconstructions of Snowball Earth events.

It looks something like this, a completely snowy Earth. Planet, there is a bit of debate about how much open water there is; In fact, there's an article published this week that argues that there was probably a lot more open water and less glaciation than many people had thought, but for all intents and purposes, the planet is locked down. for tens of millions of years, it's actually very difficult to unlock when you do that. What you need to do or what the planet needs to do is wait until enough volcanic heat builds up at the mid-ocean ridges and that gradually increases enough temperature. differential because as a frozen planet it bounces off all the sunlight and therefore there is very little heat gain from radiation alone, so if we look at the geological record of these snowball Earth events, We're starting to see an interesting pattern that really ends this for so long. period of microbial dominance that has lasted three billion years there are three main events um at the end of the precamorean uh the sturtium from 720 to about 660 million years ago uh the marinean from 650 to 635 that section of rock that I showed you uh was sturtium with Marino and above and that closeup of The Rock was the Marinoan and its global events, they are genuinely global events, um, there is a third glacial event, the gas gears, which is less global but still a really significant glaciation event, uh. and that's in 5 18. that leaves a gap of only 40 million years between the gas gears and the base of the Cambrian and it's in that interval, as we've heard in previous lectures, that interesting things start to happen, yeah, we started I see fossils like these and these are the first evidence of really abundant multicellular life existing in quite complex ecosystems and we heard Jack Matthews talk about these in the first lecture in the series and then Frankie Dunn talk about them in some lectures.

It's been um and they've been very enigmatic for a long period of time for many decades since their first discovery, but now there's more and more evidence that these are actually primitive animals and one of the lines of evidence comes from the work of Frankie Dunn who she talks. A few weeks ago, by looking at how these organisms grow and then relating that to the growth patterns of animals alive today and using that developmental biology technique, I was frankly able to determine the most overwhelmingly likely position in evolution. tree for these ediacrons as we call them um organisms multicellular organisms from India current time um is that they sit at the base of the animal tree and there are other lines of supporting evidence including preserved organic molecules that are starting to support that hypothesis If we move forward a little else through the media Cara and during that time of postgascular glaciation, then we started to see things like this.

These are animal burrows and from their pattern we think they must have been created by female-like organisms that have a plane of bilateral symmetry in the middle of the body like us, so that's most animals except jellyfish. and the enemies and things like that and the sponges, so some evidence of slightly more advanced animals starts to appear as we get closer to the end of the So, as we heard in Duncan Murdock's last lecture right at the end of the ideas car , we are starting to see evidence that animals make shells and make what we call biominerals, producing crystalline inorganic minerals as part of their metabolism. whether it's protection or um predation, so if we put all of that together into a single overview of geologic time, this is a pretty old diagram now, but it's still true at its core that immediately after the gaseous glaciation we get the entry of the edocarine . biota the idiocarine fauna and at least some of them are animals, we can be pretty sure of that, then a few million years before the base of the Cambrian we get the first trace fossils that we think were made by animals and then we start to get animals, uh, with skeletons that appeared in the last few million years, right before the Camry, so you might ask if we have good evidence of animals before the base of the Cambrian, what's the big fuss?

Why is it called the Cambrian

explosion

? What is the Cambrian? The explosion is an event that replaces environments like this. This is a reconstruction that was part of Martin Lysac's exhibit of that Newfoundland biota that Frankie and Jack described and here we have these early animals sitting on microbial mats still very. The microbial map dominated in fairly deep waters and they are replaced by really quite dynamic ecosystems at the base of the Cambria, so we can define the Cambrian explosion in several different ways in green. Here we have the EB labeled. We have the occurrence of Ed, the educator and the biota, and they have a reasonable number of attacks from different species, um, uh, particularly towards the end of their time range, but then look at that really abrupt Transit translation transition to the file Cambrian Fila animal that truly reflects the highest level. level of bodily organization they, for example, our own group is the Cordata um, echinoderms include sea urchins and starfish and are unified by um, very similar and anatomies at the next level, classes we're looking at groups still very different organisms, but for example, sea urchins are one class, starfish the first class, vertebrates, our own group is part of a class, so while we can think, I mean, think in the final class numbers and is the number of different body plans that are present and What we can see when we cross over to the Cambian is a sudden explosion in the number of different body plans that are present, so it is a boost in the evolution, is not the

origin

of animals, but the establishment of many of the body plans that we recognize in Nowadays, when we go to the beach or when we go to an aquarium, you will notice that this increase stabilizes a lot as we go through the Cambrian and we went into the audition, and since the audition there have been very few finals or classes added at all to the animal complement, so that's one way of looking at the Cambrian explosion.

Another way is to think about it in terms of ecosystem change, so we talked about that reconstruction by Martin Lysek of the Cara y biota media. on the left, um sitting before the fife from two million years ago, the base of the chamber sitting on top of these microbial mats, a largely passive existence, there were some that could move across that sediment surface, but not many They cross the camera at the boundary and, as they say here, they give it the elegant title of Agronomic Substrate Revolution, which basically means is that animals become much more dynamic and the interactions between animals become much more dynamic.

We have organisms that burrow into the sediments and begin to design the sediment that we have animals swimming in. the water column and these are recently evolved lifestyles that are associated with the Cambrian explosion. Another way to look at it is to focus on those trace fossils, thoseburrows, um, and the way that organisms interact with the sediment, uh, and that's something that Gabriella Mangano, who will talk about later in this lecture series, did in a paper a few weeks ago looking at the number of different traces of fossils that we get as we move from the bottom of the uh The Precambrian crossover into the Cambrian and look at how many different trace fossils are starting to appear and the way they're starting to engineer the substrate, they're starting to do bioengineering. in their own habitats and that allows a number of different processes to interact and increases the diversity of organisms. that they can live in those spaces in a different way.

This is a pretty complex diagram, but I'll just walk you through the essentials. Another way to look at it is in terms of the different ways that animals build their skeletons that we just looked at. I mentioned and this was what Duncan Murdoch talked about in the last lecture, so here we have the geological time from the oldest on the left and the bar at the bottom to the youngest on the left.on the right and we have a

evolutionary

tree of different groups of animals and sitting sideways on top of that and the different colored bars represent different types of minerals that animals use and it's a painstaking assembly of a large data set, but what we can say follows from this that biomineralization, the creation of skeletons occurred several times different Group B different groups chose different minerals in an

evolutionary

sense some chose calcite like starfish some like us we chose calcium phosphate and appetite some like sponges um they chose silica very few groups of Animals Once they have made that evolutionary choice, they redo that choice, it becomes trapped in their developmental biology, and therefore, if organisms begin to make their skeletons from appetite, they continue to make their skeletons from appetite, and in fact , we can break it down further into different ones. types of calcites, as well as different types of calcium carbonate, and one of the other points is that the evidence for the use of hard skeletal tissues for predation appears at more or less exactly the same time as for protection, so it is a co- Evolution is an evolutionary arms race between hard tissues that evolve for predation and hard tissues that evolve for protection, so that's another way of looking at the Cambrian explosion and these are all equally valid ways of defining the Cambrian explosion.

Cambrian. More recently, people have started to think no. in terms of individual aspects, but really looking at a unified interdisciplinary approach and again this is from Rachel Wood who will speak later in the lecture series and what she has done with Phil Donahue and other co-authors is try to bring together different data sets to look at the patterns and processes at the base of the Cambrian, the base of Fanner, Thanos Zoe, because here it says the upper linear protozoan on the left, so what you're trying to do here is put together the evidence that we have for the genes on the left . um inform is about evolutionary trees and um about the time of the origins of the groups with geochemical evidence in the Middle with the sedimentary evidence the excavation evidence um indicated by the bioterbation index with the fossil evidence the largest and exceptionally preserved fossils and if If we start to look at the interaction of all these processes, we will likely understand the dynamics of the Cambrian explosion much better.

This is something that Dave Harper and I have been trying to do for a few years and then in the green boxes we have biological processes in the blue boxes we have geochemical processes and in the red boxes we have geological processes and although it is a very complex diagram what indicates is that all of these processes are interacting and We're interacting through what we call feedback loops where the process goes around and around and starts to amplify the signal, so this is another way of these interaction processes of looking at the chamber explosion, what? How can we get evidence of all this? are the lines of evidence, well, one of the key tools that we have is that we are very fortunate in the Cambrian to have many localities with exceptionally preserved fossils and that is really the theme of the first exhibition of animals, we call them lagostats of the same manner. word that informs lager beer storage and preservation um there are many locations and I just picked out some of the key ones here um we'll hear about Derrick Briggs' hamburger shell in a few weeks and about the Chang Jiang which is also part of the exhibition, also in a few weeks, but what I want to do today is focus on the least known of these larger statins, the passive and severe biota of Greenland.

This is an image of the town. an exquisitely beautiful place right on the north coast of Greenland, discovered at about the same time as the changing biota, but much less known because people have been able to visit it much less frequently and make much less material noise now I want to spend a little time on talk about where Discovery is and how we accumulate knowledge about the aesthetics of serious records. Many people will be familiar with the story of the discovery of uh or at least the apocryphal story of the discovery of the Burgess Shale uh exceptional reserve deposit when the horse of a geologist, Charles Dooley Walcott, stumbled and found the fossils and tracked them up the hill and founded I can't see where they came from, the discovery of the serious state is not that romantic, but it is a story worth seeing here is where the locality is just at the northern tip of Greenland, there is practically no land further north than passages seriously, a little bit of Greenland and, uh, the smallest strip of Canada on the north coast. of Ellesmere Island, um, but the rest is just the frozen Arctic Ocean right on the way to the North Pole, we're approaching that piece of land, the northern tip of Greenland, um, it's hard to grasp the scale, actually , the town is around here. is a serious passerby indicated by the red dot, the closest human habitation is a Nord hideout right on the east coast, which is a weather station and is actually 400 kilometers away, so those are the most human beings. nearby, there is an alert on Ellesmere Island. the same distance and then going north, the North Pole is about twice that distance, going off the top of the diagram, from the Red Dot on the left to the Red Dot on the right, it is about 800 kilometers to the Pole North, the serious passive.

The town is situated in the largest national park in the world and the slide below gives you an idea of ​​the scale of the terrain we are looking at, so Northeast Greenland National Park has a shadow of over 970,000 square kilometers which occupies In the agreement on the red zone it is of course difficult to imagine what 970,000 square kilometers will be like, but if I told you that this red zone is equivalent to the area of ​​France plus Germany plus the Netherlands plus Belgium, that would give you an idea of ​​the scale of the the Northeast Greenland National Park um and it was explored relatively recently the early exploration um was summarized by stronger um in a beautiful series of maps in 1940 and examined the study of northern Greenland and this was his summary of um the knowledge total of On the northern coast of Greenland you will see that the coastlines were beginning to emerge at this point, probably only 10 people had ever been to this locality, studying it and mapping it, of course there were many indigenous peoples who crossed over.

This area in earlier stages, but the map was just beginning to form in 1914. You will see that our Red Dot is located right in the middle of a blank piece of land and it was only with the advent of aerial photography and then satellite imagery that we really started to get detailed maps of this area, these two gentlemen found the serious pass to the fossils and they were found during the systematic geological survey of northern Greenland, um, which I was lucky enough to be a part of right after my PhD, Tony Higgins, a British geologist, but who worked for most of his career at the Greenland Geological Survey in Copenhagen, a structural geologist but with a truly encyclopedic knowledge of geology, equally happy doing basin analysis and sedimentology as he made maps of structural geology and was working with Jack Super, who is so well known in the rock climbing community.

He was basically one of the founders of modern rock climbing, but also in the 1960s he was part of one of the last great heroic sledding surveys, sledding expeditions up the north coast of Greenland, making a geological map as they went and They worked together, and on the radio, one afternoon in July 1984. We listened to them very excited and they told me that they had found fossils. and that they had found a bunch of trilobites and a bunch of grass, we tried to figure out what the bunch of grass could be in fossil terms, it was definitely not a bunch of grass, it actually turned out to be a sponge, um, etc.

Jack came back the next season in 1985 and collected some bulk samples and on the back of those bulk samples sorry, Tony came back in 1995 and on the back of the samples, uh, John Peeling in Copenhagen, one of the paleontologists in the study of the agreement at that time. They recognized soft-bodied fossils with soft tissue preserved in a style similar to the Burgess shale and that led John Peel to raise the money for an expedition to go and collect the serious passage locality for the first time and that expedition took place in 1989. and I was part of that expedition, there was a little logistical challenge: the geological server is mapping a thousand kilometers further south on the east coast, so we were very pressed in terms of logistics.

We knew there was a little. Landing strip here, um, but the location is the same, as you can see from the red dot, it's around here, 25 kilometers away, so if we could only land at the Brainardson airstrip, we would have to carry the whole team 25 kilometers through what was known as serious passes, it had no name at the time and then all the fossils back, so we were very interested in finding an alternative solution and that's where the Icelandic pilots The twin Otter plane took off briefly and landing really came to the fore because we took off all our gear in the brain fire and then we went looking for a location where we could get the twin otter down with the gear and we went around, around, around, we went around. uh, the pilot would come onto a runway that looked likely and hit the wheels to see if they would support the weight of the plane as it was landing, put the engines back into spiral, spin, spin, hit, one of the most nauseating experiences of my life. and in the end they told us to wait and they landed the plane and it stopped literally in 50 meters.

Now normally if we are working in these remote areas the ideal solution we had last summer was to work with Helicopters but this time we only had the Twin Otter aircraft to support us which meant we had to get in and out using the Twinata aircraft and The place where the Icelandic pilots managed to land it was right on the edge of what these things can land on now, you might think this is a cleverly posed photograph, like holding the camera at a tricky angle, but if you look, the pilot is perfectly upright. and it is the plane that is tilted slightly to the right.

Uphill landing angle, um. They managed to get us down, but made it clear to us that there was no way they could land there again and take us with all the rock, so one of the next challenges was that not only did we have to find the town, but we had to build a landing strip before being able to return. Also, the local menu was somewhere in those hills in the distance, but these were pre-GPS days and we didn't have an extremely precise location of where it was, so the plane dropped us off with all of our gear, about a Ton of gear, and here's John Peel, who raised the money and led the expedition with a fun farewell, um, and then we had to take all our gear to a camp where we could build a landing strip yeah, this was the photo of the equipment and equipment for this first exploration um there was John Peel on the left then of the Geological Survey of Greenland but um later Uppsala University in the white coat Simon Conway Morris University of Cambridge um in the middle, next to Simon Paul Schiller um who at the time was also with the Geological Survey of Greenland, but then he went to work for the Geological Survey of New Zealand and then I right and that's about a ton of equipment around us that we had to cross to the locality before they could be collected, so this is an indication of the terrain, the locality is very easy to spot in aerial photographs, um, it's This white, black and white stripe on the right side, um, that you can see there and the plane that left him, it doesn't seem veryaway, it's only five or six kilometers away, uh, but you'll notice that there's a substantial river that runs down between the two and builds this big Delta here and quite a bit of water spills out and melts the ice in the field, so then we had to navigate so that the river is not insubstantial, especially in the middle of the day, when the thaw This is at its highest and that is a very perplexed Hands In Pockets, I wonder how the hell we were going to cross.

John Peale had come up with a fantastic plan to build what he called Tundra buggies, we set them up, uh, broken down and I was able to put them together quickly um and it turned out that they were a good way to cross terrain, they're not ideal for crossing big rivers um, so the only way to do it was basically heavy, we spent a whole day my The notebook says that we spent eight hours of continuous work to move the camp 200 meters and it really was absolutely exhausting work because once we got to the other side of the river we had to climb it up the hill on the left side of Those Carts, once we got to the top there, it was relatively easy and in a few days we were able to find a good horizontal place to camp.

That was the first of the carts that we dragged and then we were able to go and In fact, I look forward to the serious passive locality at the top of the hill. So this is us on the first morning walking up the hill in the vague direction of the town that Tony Higgins described to us not knowing exactly where to look and just combing through. We screws look for any fossil and it turns out that the first fossil we found is one of the most iconic serious fossils while we were walking through a screen, we noticed this particular specimen, um and now we know that it is a very primitive mollusk, but a very unusual mosque , it has a shell on each end and these calcium carbonate spicules covering the body, so it's a slug-like animal, maybe five or six centimeters long, and it was really the sign that we had focused on the town, and this was the town in 1989, a really snowy place, working under this overhanging ledge that kept breaking, and a pretty cold place to work too and you couldn't see it. more different these days um this is us trudging to the town um a little further along in the Expedition and the town is here um on this hill um but you can see that this is not just temporary There is a recent snow storm in this photograph, but most of it is unmelted seasonal snow and now the town looks like this, it is covered with grass, the snow has more or less disappeared, there is practically no permanent snow, you can see, to scale, Jacob Winter of the University. from Bristol are just starting to transport some fossils there, um, so 20 years of rapid polar melting, climate change has really changed a serious cancer beyond all recognition, but it was a pretty cold as snow expedition, um, and that meant a lot of time sitting in the tent um so again the Expedition team pumped the cello John peeled me and Simon Conway Morrison noticed Greenland's old hands at the end of the tent a has the candle B has the bottle of whiskey and then, when the weather improved, there was still the small matter of building a runway so we can get out of there before winter sets in, so one of the most unlikely entries on my CV is Runway construction, Construction of airstrip, but that really opened up the town for future visits because now, um, we had a camp with a good water supply.

We had a landing strip right next to the camp. It was a couple of kilometers on foot and 400 meters of ascent to the next town, the absolute town, and this is the landing strip a few years ago. Ready. to receive a door to door service from twin otter um more or less landing at the top of the store and collecting our Gear Up uh the next time I was able to go up was in 2009 in the interim John Peale and Simon Conway Morris We returned in 1991 and 1994 and then another short trip in 2006 and we went up in 2009 and in 2011 and a team from South Korea with Jacob Winter and the University of Copenhagen went up in 2016-17, but still only eight short trips. to the Sirius passage, as far as we know it, not as well as the other larger Cambrian environment, so some geology goes back to some geology, um we took a systematic approach in 2000, 6 and 2009 that was carried out in subsequent expeditions.

A mythology had emerged that you could only find the fossils on the screen, which is not true, they are just as abundant, but it is a little more difficult to extract them from solid rock, so while Jacob Vincent, on the right, looks to Preserve Exceptionally the fossils Emma Hamalund on the left, our geochemist from the University of London in 2011 is recording a section with me and as we build the sedimentary record, she is collecting geochemical samples that will be critical to our understanding of the environment in which serious animals lived and which we'll get to and then once the section was recorded it was basically rock breaking chain stuff um and so this is the main expedition in 2011 Emma Hamaland on the left Martin Stein in a Toyota Nielsen with his head down in the blue jacket and shouting at Rasmus and Jacob Valor and Dave Harper recording the notes and around the corner sitting on the naughty step uh Jacob came so it was a great team which meant we could make There's a lot of progress and we're really getting started to destroy the serious passive locality both in terms of its fossils and in terms of its paleo and environments.

This just gives you an idea of ​​the legwork, but here we are. able to extract relatively small volumes of rock because we are limited by the octopic twin, so the fossils that occurred in the serious step, this is, in some ways, one of my favorites because it is emblematic of the serious passive helkeria, the fossil that I showed you first it's the poster of the serious personality um but of the soft bodied organisms that have real details in their anatomy uh arthro aspis here with a 20 centimeter notebook for scale um maybe it's really implemented uh and this is just a composite plate of the variety of organisms um this is the trilobite arch and the eye of Ellis Higgins uh named after Tony Higgins who discovered the locality these are the sponges um they were probably a bunch of grass um and what I want to do is just guide you some of the components of the fauna, to give you an idea, it says there are 45 species and counting, but one of the tricks that paleontologists use is to create what's called a collecting curve and see if you're starting to carry, you're still collecting but you're not finding new species. um, and we're still at the point where we're finding new species, so there's more to come from a serious passive.

Sure it's not just that it's a foreign locality, it may not be as diverse as Berger Shell and Xinjiang, but it's certainly more diverse than the fortified species. This is first and foremost a reconstruction of Helkeria just to show you that you know what slugs they are. how it is with this armored upper surface um and this foot on the lower surface mouth to the right um and we'll see where it lived and how it was doing uh uh how we're getting its nutrition in just a moment one of the other common fossils of the fossils with subbodies , when we used to talk about soft-bodied fossils we were referring to those that do not have skeletons, mineralized skeletons, they are what we call logopods, they are more closely related to the periputo.

Modern day velvet worms and on the left and right we have two of the different genera and species of um Lobo pod and we have been able to add more details to um Kerry Michaela from the material we collected on the recent expedition that allowed for a revised anatomical reconstruction which you can see here that we published in Nature Communications a couple of years ago, of course, one of the more figurative organisms that you see both in the shale bird and in Xinjiang. the anomalocarates here illustrated with legania and these were the main predators of the Cambrian seas that grew up to one meter two meters long um with this radial mouth they belong to a group called radiodonts um and these appendages uh putting food in the mouth but but Not all the anomalous codes were ferocious and the one that Jacob and his colleagues from Sirius Passa describe to us is actually very different in terms of its mode of feeding and you'll see on the left that it has these feathery appendages sticking out. uh the main arm of the appendix um and that this appendage could flex and coil uh and the Reconstruction uh Jacob and his colleagues thought that the most appropriate thing was that he is actually using them as a movable sieve and that sieve Caris was actually the Cambrian equivalent to a bailing whale that was floating these giant energies through the water, sifting plankton and putting them back into its mouth and then swimming alongside um, we have some of the other organisms characteristic of a serious person, it was large and was multimeters long . and gigantism is something that we see in the serious past in other Cambrian localities um this is something called cyrilorica uh described by John Peale um they are the closest living relatives that we will be familiar with are things like nematode worms uh it starts to belongs to a group called Lorry Sufriance, um, but the thing about the big difference today is that they are small if you look at this scale bar down here, try again, the scale bar down here is 25 microns, um 25 000. of a millimeter, uh, while cyrilorica is tens of centimeters long, so the Cambrian representative, although anatomically very similar, is orders of magnitude larger, the group that swam alongside timothyocaris is the group in the one I'm perhaps most interested in seriously, the vets, but there's a lot of debate about which is the most closely related here we have on the left, we have a species that Jacob Dave Harper and I described in 2011 and it's a very distinctive vetericolian, we have these gill slits that open downwards.

On the side we have a large oral opening, a large mouth, so we think that the water flowed in through the mouth and then came out through these Guild slots, but on the back of that chamber there is a tail that we can see is segmented and capable of flexing, so we believe it was capable of free swimming, as indicated by the Esmond Horn model in 10 terms on the right and here, for comparison, is an example from Chenjang, so this is where Vegetables were described for the first time. and you can see very clearly here that we're all opening up as these slits have flattened out on the left and here are the gill slits where the water would come out, so this thing was taking in large volumes of water again.

It was a filter feeder and was almost certainly pulling food out of the water on the cilia of the fine hairs lining those gill openings on the side, but it was propelling itself through the water column to get the maximum volume of food. water and food in that. chamber that open chamber um if we reconstruct it and again this is one of Martin Luther's reconstructions of a chenjang fossil uh this is what it would look like as a protection on the opening so that the mouth and the right can close it and protect it uh but to feed it I would open them um and then the gills are cut to the side and the moving tail um the exhibition website also has some lovely animations um especially curling uh and swimming and feeding and these are actually quite plentiful.

They are present in quite large numbers, they have not been found in the early expeditions, but once you get a search pattern in your eye they are often quite broken down, so we now have many hundreds and are in the process of writing them up and describe them, where did all these animals live? What is the environmental setting that we were trying to understand through that sedimentary record and geochemical sampling? This is a simplified geological map of northern Greenland. The serious locality is in JP cop. Fjord which is um is here, you can ignore the red box which has a different purpose, but the key point to take a message from this summarized geological diagram is that we can divide the geology into two parts, we have the pale blue rocks to in the south are now shallow marine deposits of Cambrian and Silurian continental shelf deposits mainly limestone and deposited for the most part in a few tens of meters of water depth, but then we pass along the edge of the continental margin towards the continental slope in much much. deeper waters quite abruptly towards deeper waters and there we have mainly the deposition of fine-grained sediments and some sediments that spill from the edge of the plant make such serious passes that they are practically on the boundary between the continental shelf and the continent. slope or as it says in this diagram, the shelf and trough, if we draw a cross section, roughly parallel to the east side of that red box, it looks like this, so now we have a vertical cross section through the crust and through the sedimentary deposits um and a serious passive is found here, so it's right onthat Fletcher as we go from the horizontal continental margin on the left into the deep waters on the right um and you'll see on the left it's indicated that there are sandstones, there are continental shelf sandstones similar to the depositors in the North Sea and the west of the present-day British Isles, then we enter increasingly finer deposits as we move out of the reach of the sediment.

Supply and down in mud stones and serious passive locality. I actually drew this arrow a little too high and it's just above that boundary, that transition boundary and we can see there, so it's at a transition point, um, and a change point. in sediment supply is the first thing we can conclude if we zoom in and look at the geological map we made. You can see that point emphasized, so in pale blue we have the oldest rocks, the serious passive is that. It is located in the locality of Serious Pin it is actually within a geological unit called The Boon Formation and the bull information itself changes quite radically as it passes over the edge of the continental shelf, so in the south, in yellow, we have the typical platform. sandstones that we saw in the last diagram in the north in the pale green um we have the channel shales um and in the two darker shades of green um we have the transition blessing as it is sometimes called um which is where the locality is located serious passive and everything has been compressed a little bit because it's been destroyed by subsequent geological activity, but we can still untangle, very easily, that original tank replacement relationship, which is much more difficult to do with some other Camry in the counties, so we have a lot more sedimentary information and paleoenvironmental information to play with a little bit overprinted by metamorphism.

These rocks have been heated up to a few hundred degrees so the minerals have started to change but we can still do the sedimentology this is the locality looking east again we have these Bowen platform sandstones in B on the right we have the older Portfield limestones, which is what everything sits in the locality is this black and white stripe here, so we got the platform slope transition rocks.and then we come out to what are called the mud stones of the fjord, which are the canal month stones, if we just zoom in on the locality itself, this is what it looks like, so this is the serious passive locality that you can see here.

Here, the small quarry that was opened to extract the fossils and measure the sedimentary section, these arrows here are actually young arrows and the v in the young direction, so on the white rocks, these are young upwards, that's right how would you do it. We expect the rocks to be the serious passive locality is actually backwards, it has been inverted by this later geological activity, but we can still read the rocks quite easily and this is what the locality looked like on that first trip before we started to dig into them, so We can see the rib of the most fossiliferous material going down the hill towards Simon Conway Morrison in the blue jacket um and if we get closer to that sediment it looks something like this, it's pretty mediocre, depending on the configuration, they're very thin .

Dark gray to black rolled clay stones, but one of the really distinctive things is that they are coated in these yellow powders and these are iron oxides and hydroxides that are the result of the oxidation of pirudas, iron sulfide and that's a really key part of our history, so we've put all that together in a sedimentary record. It looks like this, it's a very thin section and the fossiliferous section is even thinner, so you can see that in the darker browns, those are mud stones, uh, going through the Palace Brown silt Stones through silty mud stones intermediate and muddy silt Stones you have for those of us who do sedimentary records, this is as boring as it gets, frankly, but really informative in terms of the environments, you'll see it on the label I've mentioned that there are abundant microbial mats and that It is a key feature of the town.

In red we have the horizons from which the soft tissues are recovered and in yellow we have where these oxidized sediments are, these yellow powders and on the far right, we have what the sediment looks like as we just saw, but then, in the bottom right, a thin section through one of these individual shale layers and you'll see it has a black and white stripe, but where are they from? my pen has now come this far, it goes from black to a sharp base, gradations from black to white gradually to black and what that tells us geologically is that these are grains of quartz and those grains of quartz are progressively replaced by mud, like this which in other words we would say that this is decreasing upwards and that is indicative for geologists that the currents are slowing down, we interpret it as the result of sediment slurries that are crossing the continental shelf, perhaps raised by storms and depositing these horizons very thin one millimeter thick, but they are transporting animals. with them too, um, that brings us to a distinction in the fossils that we find in serious passives, we can identify, as I mentioned, the microbial mats and these are easily recognized by the fact that we can see Burrows parallel to the map, so the horizontal Burrows that appear and go down through the mats um and if they go under the mats, they open the mat like um uh Jerry Wood in a Tom and Jerry cartoon um but then if they appear on the mat On the surface they make grooves so you can see this is a burrow of positive relief, this is a negative relief, Office, um, and that is, and we can see the transition from one side to the other as we come, so we follow the burial trails, um, this often happens around uh. fossils seem to invade any decaying organic matter that you can see in this image um segmentation this is one of those large osteoarthritis arthropods that I showed you a few slides ago that now live in those microbial mats it is a very distinctive fauna that we Call the Mat Guild microbial, so top right, we have one of these distinctive arthrospices that these Burrows mine for their nutrients, the worms that make these Burrows, um, we have policky worms that live in the Burrows, they don't burrow into them, no.

Brewing vertically here we have one of the arthro aspers in the middle, a halcory almost certainly grazing on that microbial mat at the top left and then a sponge sitting and filter feeding on the mat, bottom left, so that This is what we call the microbial map. gills and are preserved at the base of these small storm layers beneath the sediment course, they suffocate and die from the entry of these columns of storm sediment into the thin layers of sediment transported by the storms. the rest of what we might call the typical Cambrian fauna, we have phenomenal nominal calorie fragments and the Tunisian carus that we mentioned, we have free-swimming policky annelids, we have vegetarian free-swimming professionals, but it's also destroying. burrows um as well and some things that live on the surface, so they are preserved in a much more typical shale bird type way than the things that live on the mats, which tend to be preserved more in three dimensions. preservation in geochemistry and this is quite a complex diagram, but I just want to focus on this column on the left next to the sedimentary record, so by looking at a number of deposits a technique has been developed to calibrate what is called The smaller ratio of highly reactive iron to fet, total iron in sediments occurs in many different forms, but the highly reactive form of iron is the ion found in oxides, hydroxides, and sulfides that is now used as a substitute of the Oxygenation of the water column.

If the fehr fet ratio is greater than 0.38, we can say that that column of water where the sediment is is effectively without oxygen, it is what we would call anoxic between 0.2 and 0.38, it has very low oxygen content, we would say That is hypoxic or dysoxic, you will see both terms on the slides and you will see that the fauna that lives there and is transported a short distance, we do not believe that any of the fallen travel very far, it is quite common. um within that low oxygen interval and the low oxygen intervals are indicated by these horizontal rules, so how does that compare to the distribution of fossils in reality if we open up that diagram and look at the fossil abundance and diversity in red ? this column here the abundance and in red the diversity and also the representation of the most common fossils in terms of the number of specimens we find per unit area of ​​rock and you can see that the maximum abundances of fossils are Coinciding with the anoxic periods now you could say Well, they're just being preserved thanks to that well, that's partly true, but we also have good evidence that they live there, so these organisms live in low oxygen environments, I don't know, that's not the case.

It's a big surprise because Emma Hamilton has also been looking at the Changan deposit in China and the change looks like a beautiful beige limestone, but in reality the boreholes have shown that it is sedimentary almost identical, logically, to the serious facet, are these fine layers of stone, um and the fehr Fe tote fet um the plots seem almost identical to those of a serious person, these organisms live and are preserved in environments with little oxygen, very little oxygen if we look at the modern oceans, that is quite similar to the type of situation that we find in what is called oxygen minimum results.

They also occur at the edge of continental shelves. The oxygen is then transported to the seawater. In the photic zone, it is produced through photosynthesis. It is also hit by wave action, but as we move away from the light, the depth at which the area is found. Where the lines can penetrate through the photic zone photosynthesis stops and that means the animals are simply using oxygen in respiration, no new oxygen is generated and that results in a collapse in oxygen levels, but we still see a very characteristic fauna as it says on the left, they occupy the margins of the minimum oxygen zones, they are often quite dense aggregations, yes, quite abundant organisms, but they have little diversity, so they are opportunists that can survive there when not many other organisms can, but they encompass. a variety of different groups and we think that this is actually not a bad model for comparison with what we are finding as a serious person and that is quite contrary to a lot of previous ideas where people speculated that actually an increase in oxygenation of the oceans was what caused the camera to explode and now we are starting to find evidence that the opposite is actually true: the first animals were preferentially located in terms of their diversity in low oxygen environments and Emma has explained.

In this recent article, that shouldn't be a big surprise to us, we actually look at oxygenation from the perspective of successful oxygen-dependent terrestrial organisms, but in reality a large portion of the Animal Kingdom lives at much lower oxygen levels. oxygenation levels um and as Emma says on the left, she calls this the normal world and actually what's challenging is dealing with oxygen in many ways, so she then refers to the low oxygen world has been an ancestral niche and what we are used to. is actually the conquered niche, so we shouldn't be too surprised that the first animals are found in low oxygen levels.

You know, we know, for example, that tumor cells in cancers can withstand very low levels of oxygen and still thrive. The tools that people have looked at to try to cure cancer are to starve cancer cells of oxygen, but it actually turns out that they can handle very, very low levels of oxygen, so maybe we should reverse our way of thinking about cancer. animals and think more about the norm. Since they evolved with little oxygen, so in the last few slides we can put all of that together in an environment where the severe passive locality is indicated by the red star which is located right on the boundary of where sediment transport would occur in these storms. reach, so we have shelf storms, increased enormously, um exaggerated gradient, um sandy shelf storms kicking up sediment, flows across a very gentle slope below the base of the storm waves into that oxygenated zone, buries our microbial mats, preserve our Serious organisms, um, right on the shelf slope, are strange, so if we look at what drove Cambrian evolution and the Cambrian explosion, we can be more or less sure that it wasn't oxygen because it was oxygen that maintained key control.

It will be on the inner shelf where there was a higher level of oxygen and yet what we have is the sediment in which the organismsThey live here and are transported a short distance to that locality, so they are in it while we are. I've seen a pretty low oxygen environment if they were driven primarily by nutrient supply. Additionally, they will be further inside and show that they will be within the photic zone where the maximum nutrients are found. There are some specialists, some vertical burrowers called living skeletons. In the shallow water zonation in this time interval we have seen what Scotland was, for example, but one of the things that could be controlling where these first organisms live is the mobility of the substrate.

It may be that they really were not very tolerant of mobile substrates that would be moved by currents and that are settled on microbial mats, um like almost the most stable foreign and other Cambrian substrates, the largest of others, exceptionally preserve the Cambrian deposits like organisms that lived in deep darkness and quite smelly water, um, and not the crystal clear tropical waters, um, that you see in some reconstructions and this rather nice diagram by Martin Lysette for the exhibition, I think characterizes this for Chang Jiang, but this is pretty much the environment I also foresee a serious passive and I'll leave it at that.

Thank you very much for listening. Many thanks to Paul for a wonderful and wonderful tour. Please continue to enter the chat and we will try to get as many answers as possible. We can before we continue with that, just a reminder that you can find all of our previous talks and in fact the pulse will increase over the next week on the museum's YouTube channel. I just put a link in the chat, um, right? now and just a reminder that if you enjoyed tonight's talk and then feel free to share it online, share the link with friends and family who you think might be interested too and then at that point we'll quickly switch to This is because we are very pleased to say that we have our agenda sorted for the next few months, so our next talk in two weeks will be by Professor Sarah Gabbert from the University of Leicester, who will talk about some wonderful research that she has finished discussing experimental Decay and what this tells us about fossil preservation and the link to sign up is now live and I just showed it to you and two weeks later we have Professor Shuhai Zhao. from Virginia Tech, two weeks later, Professor Derek Briggs from Yale, we have a parade of

professor

s for you and then, as Paul said, on September 9, Professor Gabriella Mangano from the University of Saskatchewan in Canada will join us and to end.

Everything will be ready on September 23. We have Professor Rachel Wood again from the University of Edinburgh. You have an idea of ​​what you might talk about in one of the slides tonight, but put them in your journal and as If we receive more details from our speakers, we will post some registration details on the website and of course share them in other chats and, just before we answer some of your many questions, we just remind you that we love getting a little feedback and would be especially pleased to hear your thoughts on this question. Did this conference change your opinion about the evolutionary origin of animals or contribute to your understanding of the topic?

If so, how and do you have any ideas about it? Do it in the chat, but At this point, let's move on to some questions and I thought we could start with some interesting questions about your fieldwork because it was a lovely insight into how fieldwork happens in these very challenging areas, so we had some questions let's group them all together. together um or let's do them in two, sorry, first we have a question from Morrison, what has the transition been like from snow to grass due to global warming? May has made it easier or harder to find the fossils you're looking for and Margaret asks a very good question, wondering if any of the indigenous people had stories or understood the locals, um in terms of the ease of finding it, I guess is what we would say, swings and roundabouts, some win, some lose, so my overwhelming memory of the first expedition was and the first expeditions at that time were in slightly cloudy conditions. um really quite cold, couldn't feel my fingers, but when looking for fossils with a serious pattern, good light is really critical. um and on recent expeditions I could Look, but we've had much better light.

The downside is that the increased grass and humidity has resulted in a lot of mosquitoes which we never used to have in that part of northern Greenland and there are days when. it said in an old Arctic exploration story I was reading a few days ago. The only way we could fit more mosquitoes into a cubic meter would be if the mosquitoes were smaller. That can be a bit unpleasant at times, but generally stable sunny weather like this. Photography would be my go-to there every time. I mean, it may still only be four degrees, but it's great weather to sit around and collect fossils all day.

In terms of indigenous peoples, there have been none. indigenous peoples this far north for quite some time there are some archaeological remains of Paleoinuit settlements they were probably transitory settlements um scattered along the coast they probably never got very inland because that's not where the food was um but uh so I don't know of any indigenous accounts about geology or super and I'll stick with field work. Three more questions about the shark. Laura wants to know if you have to worry about polar bears. Morrison wants to know how you control it or protect those specimens. and you have to worry about the cold, you know, and about transportation, and then William asks us about these fossils from this expedition at the Oxford museum, take the last one first, um, yeah, some are being studied, so there's some in my office, The Bachelor Collins that I mentioned and some uh were on display as part of the early animals and you can see them on the exhibition website um the main collections of important fossils um are in Copenhagen um at the national history museum natural there but really they are just kept under management because the ultimate goal is to get them back to a museum in Greenland at the right time, so all the material that we collect belongs to the geological, to Greenland and the people of Greenland in the government um and that's where the material will come back and that's where it should come back remind me of the other questions Jack so the other questions were how do you protect the specimens for transport and do you have to worry about the cold and Laura wants to know if you have to worry about polar bears, yes, in terms of protecting them from the cold, that's not a big problem, more of a problem is the fact that they are reasonably fragile, so we pack them up. very carefully, either wrapping them in cloth and cardboard, John Peeler, the really good system of taking a flat pack, cardboard boxes, and rolls of foam, and then we would just put a layer of foam, a layer of fossils, a layer of foam and then fill the box, pack it well and you can more or less kick them around the track and the fossils will not be disturbed.

In terms of polar bears, polar bears don't bother us, but they live there. I have seen it. them on the ice in JP cockfield that for you uh in the background uh from a helicopter, which is one of the best ways to see polar bears, but we carry big, big, big, high color guns for caliber rifles, uh with us and we keep them in the tents at all times in case they bother us. More recently it has been wolves, in fact wolves have started to become more abundant in northern Greenland and there is a fairly active pack in a serious passive situation, but they are kept out of our way by the way they are quite shy in for the most part and about some questions about some particular specimens and the fossils themselves, we will start with a question, my Jiang, who asks: How curious two shell-shaped segments suggest a close affinity with brachiopods or bivalves?

Or is the resemblance only superficial, so it is largely superficial when Simon first looked at it in that first specimen and came up with the charming hypothesis that it was the missing link between the brachiopod amyloid worms and the mollusks that we now do we know? that sit on very different parts of the animal evolutionary tree, um, but Jacob Winter's work as part of when he was a student, actually a master's student, showed that uh halkira is a primitive mollusk, so the way that grows is its shell is Analogous to the way clams or bivalves make their shell, so the two shells at both ends are more similar to bivalve shells, but then they have all these spicules in the middle that are part of this arm and these sclerites like us.

Call them arm parts and Joe Botting wants to know how similar the sets are from bed to bed. Well, Joe Botting, the Sirius sponge expert, the man who was published in the Sirius passage sponges, uh, so it's not entirely a naïve question. Joe, thanks. A lot, so, um, the general composition of species we sample at 10 centimeter intervals throughout the entire Section just to be able to do that census, um, and it's the same set of species, um, but, but when it is, um, when it's a particularly high diversity interval. only the rarest items come in, so there's not much, there's no particular gradation in the fauna from the bottom up, questions and a nice open question from Marc Jacobs who wants to know what your favorite find was.

I guess it would have to be Halkiria. I didn't say that during the lecture, but I'm sort of tripping over it, so picking up on that and realizing that you know we found the locality and we found a pretty interesting fossil at the same time, but was I? I think it's one of the best fossil discovery moments I've had in my career. In fact, we always like to hear about favorite fossils or favorite areas of geology. Moving on to some questions about trace fossils, I'll put two questions together here. um Frederick would like to know how you can tell that something is bilateral by the shape of its burrow and Denver asks if the evidence of animals through trace fossils in the Ediacran is still valid, since Mariotti et al have shown that the Microbial mats can form such tracts that are supposed to be made by animals, yes, that was a very interesting article, um, I think it's one of those cases where you know exceptional claims require exceptional evidence and it's tempting to JUMP on older deposits in your car and deposits and claiming that things are made by animals I think there are undoubtable um horizontal Burrows in Karen's latest idea that we would all be very happy with um and if Frankie were talking now she would say I think there are some evidence that um at least some of that idiot car and the biota were also able to move and disturb the substrate, um, yes, there is definitive evidence, I think from my perspective it is definitely good, um evidence for Burrows, there is good evidence for the districts with the best education, um, in terms of bilateral symmetry. the sinuosity pattern and the fact that the city can divert it um that type of excavation really depends on the peristalsis of the swallowing actions that we push a bolus of food down our throat that is peristalsis um and it is peristalsis that only bilaterally symmetrical organisms possess that allows for excavations of that type too is for what it's worth, probably allowing for that primitive swimming that we also see in some groups, um, so the evolution of peristaltic muscle movements is actually a key innovation in animals and Sid off asks a question which is how can we calculate the age of the fossil so I'm going to be a little more specific about how we know the age of the fossils in the Cirrus passage oh, that's a very, very good question, very good and It's taken us a long time, it's much easier to describe a good soft-bodied fossil than it is to try to estimate the age, biostratigraphy is difficult, that's partly because we can't use precise arcs, these little spores, which we use frequently at this time.

Horizon due to metamorphism the rocks have been heated to a point where they have burned up they are just carbon the only thing we can use is the trilobite that Ellis Higgins Army makes um but it is only known from Passage serious um so Then we have to take a series of steps to correlate Boone Ellis and his relatives to more complete sections in central North America, where we have more complete stratigraphy, so that's one way to do it, but we can. we can verify that because what we can do is use sequence stratigraphy, which is the record of sea level rise that is in the sediment and there is a serious liability, and I didn't particularly talk about that, it is located right at the base of a major sea level rise and that is a major sea level rise that we can take immediately across the entire North American continent and on the way across other continentsIt's also a very distinctive time that fits Horizon um and they both give the same answer that It's essentially a serious person is the same age as the chain change and is sitting at the base of the Cambrian series three.

Okay, there are a few questions left, I think, and then we'll wrap it up, but great one from Sarah, why do you think the Cambrian? The explosion happened when she did, so I think it was going to happen regardless, you know, everything was in place. My instinct is that what acts as a trigger for that real acceleration that we saw in the histograms is the sea level rise that I have been talking about for many tens or hundreds of millions of years that the internal parts of the continents have not been flooded. and sea level was at or below the edge of the continental margin, but for a variety of geological reasons, one of which is an increase in plate tectonic activity that raises global sea level and floods the interior of continents for the first time increasing the area in which organisms can live within a given depth of water on a slope that you're going to fit in a small area, if you spill all that water across continental shelves of low gradient, you will have a much larger habitable area and what ecologists know is that species diversity is closely linked to habitable area, so sea level rises. it increases the habitable area which then provides the evolutionary drive to produce the exploding chamber in my opinion and let's ask a question from William: do you think we will ever have a snowball Earth again?

Yes, but not for a while and so, in closing, Go to Eleanor Straw's final question, who asks if she had unlimited funds what would be the ideal place or thing to investigate to help her understand the Cambrian explosion. I think what everyone would answer to that question is that we need more seats. We need them in other places, we need them, so we have them in Australia, we have them in China, we have them in North America, we have some in Russia, but what we need are more locations now. given my predilection for arctic things and with my unlimited funding I would take a helicopter and jump along the Bowen Formation in northern Greenland and because severe passive locality must occur elsewhere and although we have searched that small area around from the town and found some fragments of that outcrop belt as we call it, that band of rock extends for about 300 kilometers, so that's my fantasy helicopter trip.

Thank you very much for the last question. We look forward to your donations. towards the back of Paul's field, sorry for all the questions, we couldn't answer, there were so many, but we hope to see you here in two weeks for our conference with Professor Sarah Gabbert from the University of Leicester, who is I'm going to talk about the experimental decay and the wonderful world of rotting fish and what that tells us about fossils and preservation should be really exciting so join us in two weeks and the link for that is in the chat but um and do it . put your answer to the questions on the screen now in the chat, but from me at MU at the Museum and from Paul, thank you once again Paul for a wonderful lecture and we hope to see you again in two weeks, thank you. thank you so much