foreign [Music] hello and welcome to technically speaking where scientists and Engineers come together to chat about a common interest share knowledge and satisfy some curiosity I'm Laura and this time I'm joined by Ellie to talk about how life evolved in something known as the Cambrian explosion and the animals that were around at the time so Ellie hero zoologist there's an obvious connection to the animals there so tell me about your interest yeah I think it's pretty
exciting the Cambrian explosion is one of those things that think all zoologists is all about the animals that live now but to get to the animals that live now you have to go way back in geological time and the Cambrian explosion is where animals get the good stuff they stop living in the Marine environments and sort of just Milling about and they come on to land and they start developing all different characteristics and that is really the start of where we get animals that lived
500 million years ago those are the ancient ancestral lines that now persist all the way into today okay so I remember vague things about this from my undergraduate degree which involves earth science and looking at the rock records and there were things like a rocks essentially eat each other so the rock record only goes back so far so if the Earth is something like 4.5 billion years old The Rock record is only about 4 billion years so there's a bit of a gap but we're not looking quite that far
back in time are we no our magic uh seeing eye does not quite go back four and a half million billion years it only goes back well today it only goes back about 540 million years-ish oh and is that when all this sort of stuff was taking off yeah so I think there's a little bit of discrepancy because obviously it was so long ago but most people sort of agree that the Cambrian explosion was between 541 and 530 million years ago at the beginning of the Cambrian Period in geological
time and I like the word explosion makes it sound really sudden which I guess in geological time scales it probably is yeah so I think most people think of an explosion as like they've been watching Oppenheimer and it's one massive boom uh but this is much more like comparatively so like Evolution takes millions of years but in the time scale of all Evolution this was the period of the most rapid evolution in Earth's history so all the all the evolutionizing happened a lot quicker in this period
uh than it does then before or after and it was the idea that I think as well that you got this this huge increase in biodiversity essentially I think I read browse through a research paper that was in the period before that there were some animals but they look really weird compared to the ones today which makes them difficult to classify and it kept hammering this point that they were weird they are they are super weird basically before the Cambrian explosion
everything was just sort of floating around in the sea there was a microbial mat uh that like they fed on sort of but they were all very soft and so like not well preserved in the fossil record we don't know largely lots of the stuff that was alive then because to be preserved it helps of you have a hard shell or bones and lots of this stuff was squishy and Squishy doesn't preserve well unfortunately no I was reading up on this um so it's it's certainly the spaces
within the bones that um they get mineralized as groundwater flows through the Rock and they fill those spaces and leave mineral deposits behind and is the organic matter decays away that's what what's left it's the things in the gaps in the bones it's a strange sentence and I think the squishy things are only preserved in areas where there was um iron sulfide I think it said oh it's not necessarily the case that all squishy things are never preserved but yeah just you find a lot more things
that had hard hard Parts yeah it does make me wonder about well what kind of squishy things were around that we just don't know about I mean probably I think I think weird like that's the Cambrian explosion like pre-cambrian explosion there were like many legs and like technically bits and floaty worm things is yeah strange strange suspicious creatures now but then there was something that caused this huge increase in diversity and I think a lot of the reference I saw
said body plans that we recognized today so I guess having like defined like two arms and two legs or spider-like thorax and many legs that sort of thing is that right yeah I think so I think it's sort of like most stuff is a chew s very basic level people you have an in and out and then once you get past this Cambrian Period things get legs things get Vision things get bigger and then it becomes like they get the good stuff they get cool things adaptations to
different niches and they stop being quite so sort of squishy and flubbery no but still squishy inside within and in and out I guess yeah still you've still got the you've got to start with the tube that's what that's what we say and then build upon that and you know things that lived in the sea were a tube that didn't move and then you get tubes that are moving and floating and then they come out of the sea and then the tubes start chasing other tubes there you go that's the
history of entire evolution in another shell so say a physiologists tubes guys uh and you mentioned that it's it's pretty much just what is preserved in the Rock record and I do vaguely remember some of this from my undergrad degree but do you have any more information on how we know what happened and when so lots of uh very clever people that don't describe stuff as just you tube uh we'll look at these animals that have been preserved and so you can see then what arose and how the filer that
survived uh became Modern Life so it's kind of hotly debated about what happened and when and who was living when and all this sort of thing but grazing organisms were largely present before the Cambrian explosion this is what sort of gets preserved there were microbes all over the sea floor it was extremely low oxygen environment and then you can see in the record what is preserved then after that period is very different there's quite a lot more that's preserved and so then you get
this big explosion that was the Cambrian explosion as it changed over these several million years cool and I think what I remember from my undergrad degree was it was like a combination of figuring out what else you know from The Rock record that's nearby and doing things like um I think it's radiometric dating I think carbon dating is the one people are most aware of because you see it on TV which is looking at different isotopes of carbon in a material but that only
works on things that we're still living at the time so if you've had um a fossil where all the organic matter is then being replaced with minerals instead all that carbon's gone so you can't really tell so you have to use something else hence why you sort of look at things around you and I think carbon dating is only good for sort of things that are less than 500 000 years old so instead you can use the decay of natural uranium it eventually decays to lead so you can
look at the ratios of uranium to lead in your material and use that to figure out how old it is that cool I never would have thought that yeah and it's a bit more sort of longer lived but it's still um a longer lived isotope I should say I think she says not remembering any of the um radiation signs she's done recently but it's still not that straightforward there is like other things take into account so it's like one tool in the paleontologists toolkit for figuring things out along with what
else do we know and a whole load of other things yeah it's also the context as well of like where it was found what the rock type was like that it was found in what things were found near it is often quite a good clue like you can get lots preserved in one area from a certain time there's quite a lot of papers and examples of like the burger Shale is like a super common one where loads of things were preserved all from that one time period And scientists go back there regularly
and dig up more stuff and find more cool animals that lived millions of years ago so tell me more about these animals what's the most interesting one in your opinion now I think I asked you this before actually in a more modern context this is this is mean now um let's trilobites I think you can't mention the cranberry explosion without mentioning trilobites they're cool they preserve well they change as well so before the Cambrian explosion they were quite soft they were swimming around in
the sea doing their own thing and then because of what happened with the changing environmental conditions and the explosion taking place over millions of years they come out and they get harder and they get a bit more sort of I think like horseshoe crab like and they get exoskeletons and they think partly this is because of the change in oxygen so pre-cambian explosion there's not that much oxygen on Earth essentially so everything's living in the sea it's very low oxygen
environment and then this big change takes a place where suddenly well not suddenly several million years but effectively suddenly there's a much more oxygen-rich environment and the levels of CO2 and oxygen are sort of changing quite a lot and they think that allowed organisms to begin to leave the water and develop different ways of of doing things okay because I was under the impression that animals officially left the sea after the Cambrian explosion but
I guess it's open to debate as to what do you mean by that because they were apparently going out likely to be going out the water a little bit initially then going back in and sort of living on that margin and at which point did they then just not turn back I think seems a little bit contentious yeah it is contentious and a lot of people think this like the Cambrian explosion wasn't like single thing like a single it was on this day it's like an evolutionary
period and because it's a time scale it then like bleeds into different like time frame so you couldn't say definitely or it started exactly 541 million years ago and it ended 530 million years ago but you could gauge based on what we've got in the fossil record that it was probably around these times and that the actually the Cambrian and the accordion sort of bleed together and some organisms preclaim green explosion survived into what was then the Cambrian and some didn't and then
some evolved because of what happened that weren't alive before so yes very much fluid it's not a one significant habit on this day for things that lived in the sea that are mainly tubes he said that the oxygen levels Rose and I read it was one research paper I think that said that was partly because there wasn't any free auction around on Earth initially way back though four and a half billion years ago and it was bacteria essentially that started to produce the
oxygen although some of it will have been produced by um ultraviolet rays from the Sun hitting the atmosphere and breaking oxygen molecules off gases but also that there were a lot of rocks that weren't oxidized and they absorbed a lot of the oxygen which didn't leave in a lot in the atmosphere for anything to do anything particularly useful and it was only once the Rocks had become oxidized which I think it sounds a little bit weird and I don't know if it's more than
one research paper that says this but I guess it kind of makes sense that this sudden increase in oxygen content sudden in geological terms might tie in with something becoming fully saturated I think so I think the idea is that oxygen levels sort of function of collagen so this is like you've seen the trilobites they get harder because that uh change in oxygen means that they can make these proteins that make hard structures in the body so it's sort of like all ties in to what you're saying
that more oxygen means like a change in the animals hmm it's got me curious now about how collagen is made but I feel like that's probably no because like instinctively I would assume that they need the harder exoskeletons to emerge from the sea and not just turn into mush because they're not being supported by the water around them but it makes more sense that that adaptation came before they left the sea yes I mean things weren't really living in the deep sea it's not like they were
you know two kilometers down they were sort of in the shallows as it was anyway so they wouldn't have had the sort of you know how things get really weird when you go really deep in the sea but then yeah they would have been like a bit more they would have been shallower anyway so they wouldn't have needed quite so much support I suppose or maybe they would I don't know that's an interesting one hmm it's the first place my mind went to it's probably completely wrong though
just seems logical we've done a collagen episode haven't we we did I don't think we looked at specifically How It's Made initially like what I mean most things have got oxygen in them yeah that's true I can imagine they would probably be in other factors rather than just all the rocks that stopped absorbing the oxygen because as I said the rock record um isn't complete and rocks eat each other there must be more to that and I remember from my um undergrad degree
looking at paleoclimatology and this was 20 years ago by the way and it was sort of like it's climate change really happening because of what people are doing or is it just one of those things that's happening anyway because there's a there are factors like um orbital forcing where the Earth's orbit isn't incredibly stable on geological time scales and it wobbles very slightly so sometimes we're on average slightly further away from the Sun than we were in the previous few million years and
that difference affects how hot it is I mean climate change is happening yes we know that now yes this is like 20 years ago when we were like well people could be having an effect like human activity could be having more of an effect versus what's already happening and we don't have all the data to tell us now we know science has moved on a lot in those two decades but way back when when people weren't doing stuff and it was just the bacteria apparently in the natural
processes things are probably a bit different um I think I read that the oxygen content varied quite a lot from anywhere between like five percent to 35 in the early part of Earth's history whereas now it's pretty much 20 I feel like I should know that I should be more definitive when I say it I think there's always scope to learn new things you have to know all the answers all the time no it just seems like a really obvious one that I should know but I'm a bit ill so facts are not
going to my brain the way they should I'm a bit under the weather I think also what's interesting as well is that there was sort of an ecosystem before what we call the Cambrian explosion period but what happens as well is that like you were saying that the sun and the carbon in all the Rocks nutrients that eroded from the Rocks were then washed into the ocean so that could have also been part of it providing that calcium and phosphorus to help build like skeletons and hard shells
so also around that time like more niches were available for the animals to live in so before they'd all sort of been in the same area but once this happened animals start burrowing like into the sediment of the bottom of the shallows and then they're stirring up the sea floor and stirring up more nutrients so this sort of helps a lot of things happen is suddenly you've got all this availability of different things that you never had before then you can exploit that and animals
will you know adapt and evolve to explore all these different things hmm so I guess there are at least two things going on there there are the chemical changes caused by changing climate or changing environmental conditions the oxygen and the washing away of the nutrients into the sea from the land and there was also a change in animal behavior if they started to dig yeah absolutely so there's also that and then because of this you start getting like the first more complex food webs and like
predators so before that everyone was sort of I guess eating the same things or feeding on microbial life but you get bite marks in the fossil record and I think that's so cool and like some fossils are so well preserved you can see the gut contents so you can see that they were eating each other which I think is amazing wow you've got to wonder at that first animal that thought oh I wonder I wonder what will happen if I just eat this thing sitting next to me
yeah I think that's incredible like how did they go from just sort of eating I guess algae and microorganisms and bacteria to then being like no I'm gonna have a go at you and see if you're tasty yeah I guess there must be something in there about like if you think of like Plankton or whatever else it kind of floats around in the seed it's just whatever happens happens but if you're a predator you're sort of actively going out there and finding food at that point
yeah so you can see how much more complex they got from like relatively simple organisms that were living in the sea and you know not doing perhaps as much complex behavior and then suddenly all these nutrients come in animals are evolving in different ways there's different niches to exploit and suddenly all these complex relationships form between all the animals and they're chasing each other and and eating each other and you know being cooler see this is what I
said this is Cameron experience where you get the good stuff suddenly you get much more complex relationships much more complex body plans like the animals are changing themselves and it all happens in a relatively short period of just several million years relatively short this was way before the dinosaurs they were wiped out 65 million years ago I don't know when dinosaurs were first considered to have been when they were first seen in the Rock record it's probably more accurate to say that's
true when did dinosaurs like officially start because also there's a big period like people get confused because of stuff like Jurassic Park and all the rest of it but T-Rex and Triceratops didn't live at the same time like there's a big gap between them and dinosaurs got wiped out 66 million years ago but there was a long time before that where they were living and different species went extinct at different times like they all weren't suddenly wiped out in one go sort of
thing yeah I guess again it's about they were adapted for a particular environmental conditions and then they changed so they know their Niche stopped existing they can't work out if we need to Define what we mean by Niche because we both know what we mean yeah that's true I just Googled it because I was intrigued dinosaurs appeared in the Triassic period sort of 250 200 million years ago so you can see again they've got a long period if they all get wiped
out 66 million years ago they were still alive well not all of them but you know I mean for a big period of time yeah far longer than humans have been recording this information definitely but yes knee say or it's a good definition like a specific habitat in which an animal lives and is evolved to exploit the resources within that habitat so I guess a good example going back to what you're saying about when you get into the deep sea things get weird you'd have things near the surface that like
sunlight and they like it being fairly warm with a particular nutrient oxygen composition yeah high level of oxygen low level of pressure yeah and the further down you go the deeper it gets the darker it gets but then they've evolved to live in that area and do it well like that they've evolved into that niche of being in the very deep sea and then the other animals at the top living in their Niche at the top of the ocean yeah and the two are unlikely to meet but I guess the ones the bit of a
crossover for those intermediate levels yeah also the thing you have to remember is that animals don't read the textbooks like I find this so funny this comes back to me quite a lot because you can say oh I don't know the Dumbo octopus lives between two kilometers and seven kilometers deep in the ocean and then someone would take one of those fancy you know underwater submersibles and they'll see a Dumbo octopus and it'll be only a kilometer in the ocean you know
they're doing their own thing it's just like observation isn't it that's how we learn yeah so sure it's like every time I try and identify birds in the garden it used to be and you'd look at idealized sketch on the rspb website of what one's meant to look like with these very perfect colorings and you go I don't think it's that but I don't know what else it is because there's natural variation so the textbooks can't Encompass at all you're looking at it and you're like is it a dirty Robin or
or is it something else entirely yeah there's a blackbird around here actually that's like brown and black and I keep looking at it and going it's definitely a black bird but it looks so weird but it's probably just you know mutated or it's got one of those color morphs or something like that but yeah it's definitely yeah convinced it's a black bird it just looks the wrong colors it but it moves and acts and has the same shape as blackbird so it must be like nine markers out of ten say it's
a blackbird exactly exactly speaking of birds and dinosaurs I think what's quite funny is that dinosaurs basically evolve into birds like that's what we have left like dinosaurs become birds and then if you go all the way back to the Cambrian explosion like the first chordates the first animals that will eventually become humans evolved during this period and so do loads of other relatives so crabs relative to Crustaceans they all started to evolve starfish sponges worms these
are all like animals that were preserved in the fossil record all these early ancestors and then persisted and changed and evolved but because of what happened then is why we get these Crustaceans and starfish and mollusks and everything else from the Cambrian Period and us which I think is really cool ah of worms really evolved all that much if you have everything was just a tube before the Caribbean explosion I was quite a lot of worms and also you get parasitic worms which I think is
slightly different so there's I think worms get perhaps not as much uh you know trilobites are funky but Charlie bites went extinct like everyone loves a trilobite but worms are still going yeah what's the difference then what is there anything specific that killed off the trilobites in the end because they I seem to remember having quite a few like different there are different classifications of trilobite not all trilobites are equal like same with I did a project in my undergrad and
ammonites you had to classify different swirly shells which was quite difficult yeah when you look at it so they they kind of like you know spiraly shells and they add to their shells and segments so you had to look at the shape of each join and try and figure out does that shape look like the same shape from this one so is that the same ammonite when you you're taking again like these 10 identifying points or whatever they are into account surprisingly hard so what
killed off the different types of trilobites the trial about is down died out at the end of the Permian so 251 million years ago so they were alive for a pretty chunky period of Earth's history uh but they were wiped out by the Permian mass extinction event that I mean to be fair everything was wiped out by that that was like 90 of all species on Earth were killed by that event and it was like a huge environmental change it's not like that it can't all be asteroids right that was
just the one event that probably most likely killed the dinosaurs yeah because there have been things like ice ages haven't they and again the extinction event it's not sudden no exactly there's a thing that happens and then there's a long period of time of Fallout of because of that thing so is there any agreement on the end of that era or period in geological time um sort of the end of well I suppose the end of the Cambrian then continues for quite a long time and then you get the
order vikian which I can never say um I always say it's all division but I don't know why and then you get more corals and you get funky things like nautiloids but then also stuff still dies off right so the world doesn't stop changing after the Cambrian explosion there's still lots of environmental changes there's still lots of things happening but not quite as fast as during the Cambrian but yeah afterwards in the old division I've learned it now lots of marine
species day off and then you get the slurian and then you you know carry on and carry on until you get to the dinosaurs and eventually modern day animal so at some point during all this animals although they might have been emerging from the sea occasionally we'll find like right that is it we are definitely on land now there might have only been bacteria before us but now there are animals and presumably before that there were plants I read one research study that was they were really
interesting how eyes had evolved and why they'd gotten bigger yeah so this is part of the Cambrian it's like suddenly stuff gets really good eyesight yeah and they reckon part of it was like they started to see food on land and they thought oh look there's more stuff over there and no one else is eating it yeah I guess it's part of it like compound eyes become a thing during the Cambrian explosion um yeah so maybe they were literally like hang on a second if we can see it
then we can eat it yeah and apparently that was the main impetus for leaving the Seas as you say there were more niches available and this Niche was not yet filled yeah and also think of the it's like if you can see but the animals around you can't surely you're going to be better adapted to the situation to the conditions to avoiding these predators that are coming in uh and yeah therefore be more likely to survive which is perhaps why like compound eyes now are quite prevalent you can imagine
though so I the food webs that we currently have today it is the napex predator and their population is sort of controlled by the amount of food that they have yeah but back then if there was nothing else it's just you and all these plants I don't know about plants I I can't say for certain one way or the other when the plants came what the plants were doing I have no idea I'll be totally honest and I'm sure I'd read it was before animals definitely were deemed to have
left the Seas permanently but I don't have a notes in front of me to back that off because I was focusing more on the animal side of it it must have been in this huge state of flux right the food webs are usually fairly balanced the ones that we see today unless humans have interfered somehow so there's enough food to sustain that Predator if there are too many predators something has to give in that top part of the food chain but back then if you don't have that like how easy would it have been
for these animals to sort of go nuts and wipe out most of the plant life just have like a massive all you can eat buffet on all the plants that were around and then they've suddenly done themselves in because there's no more food left and they can't they can't get more food I don't think that would ever have happened I think Evolution would have been a bit slower than that I would have thought so I would have thought so it's difficult to know I don't really know what was
around at the time in the Rock record isn't necessarily a complete picture is it no absolutely not yeah no and I can't imagine any scientist would ever publish a research paper saying well I think this happened but I don't have a shred of evidence yeah I think you might get uh pulled out at some point yeah but I can imagine a lot of um paleontologists sit around saying oh well maybe what about this let's throw some ideas around it could lead somewhat yeah well the thing is we don't know
right we can't go back 500 find out when the plants came or what was happening or why this happened for certain we can only make inferences based on what we've got what's in the fossil record what survived so yeah we could be missing a huge piece of the puzzle and we could never know you know we we only get further away from what happened but then I guess techniques that you were talking about earlier how we know the fossils are however old they are those things change
the technology changes to allow us to look back in time maybe a bit more easily but yeah I guess you can never know or say for certain why this one thing happened versus another thing but I'm sure a lot of people have a better idea when the plants came because I have zero idea I think it's something we can probably look up for a future episode it's just not something I focused on when I was researching for this episode no I think the Cambrian explosion deserves to be about the
animals and we will focus on the plants we'll give their plants the due attention when the time comes is there anything else that you know about the Caribbean explosion that we've not really talked about it's worth mentioning oh that's a good question um I think there's more to it than people realize I think it wasn't just five things living in the ocean that then decided that they were going to become hard and live on land like there was a lot going on and then it changed
very rapidly because of all the environmental conditions and all the things we've made and then it became life on earth like that we know of we can trace stuff back 500 and however many million years to stuff that survives and I think that's the cool part of it and I think well people say that the camera explosion is like the most significant evolutionary event in Earth's history and yeah but then a lot of stuff came after and I'm sure lots of people argue that
other things were more important but I like the Cambrian explosion but you know what you were saying about there is stuff that probably isn't preserved that we don't know about it makes me wonder going on with my weird animals rampaging and eating all the plants theme like what may have existed that we have no way of knowing about oh that's fun I mean even the stuff that did exist that we know about is pretty funky so you can only imagine it was even weirder the classic Canberra an explosion
picture that I have in my head is one of those I don't know if you've ever seen a picture they're called like Amy something these animalocardus and it's sort of like a fan with a long body and then sticky out eyes they look very peculiar but they really lived like we know that that happened but then there must have been so much other funky stuff that was much more like soft and flubbery and maybe more Squiddy things but then squids are quite complex so they probably don't come into it until
much later a simple squid simple squid yeah something like that a simple squid that's just what the squids have brains or is that something else I'm thinking of I thought so something compared on my news feed it might have been yes and then it ended with the we're doing this we can figure out how to put like brains on chips or something like that and I don't know any more than that but it sounds like an intriguing future episode absolutely yeah I want to know where
you're going with that no random tangent it's quite difficult to try and imagine stuff when there's all this like diversity of Life out here already yeah and then like think of something that might have existed a long time ago yeah see I wonder if there might have been something in the atmosphere that obviously can't be preserved in the Rock record that was actually quite large like not bacteria oh that was like floating around up there somehow absorbing stuff out of the atmosphere
which I'm assuming would have had a lot of CO2 yeah and possibly some other carbon containing gases how old is it also then sulfur from volcanoes I'm imagining like flying carpet sort of shape but like really thin and like like sort of like a manta ray but not as cool like just yeah good at absorbing things or weafer thin like almost transparent yeah like ghosts with no eyes or like really simple eye structures yeah or because they're floating around in the atmosphere they're essentially balloon
animals yeah oh my goodness me ah you never know I think before the Cambrian explosion one of the biggest oldest animals is essentially this like floppy bath mat is described as it was in the sea not in the sky yeah these like microbial matte things get mentioned I think people aren't really sure what they were like it's very hard to know like the definitions haven't been developed like we only started naming stuff once we evolved and then you know get to Darwin and all the
rest of it and innate us so all the stuff that lived before we don't necessarily have the categories or The evolutionary trees to know what it was or like where to put it so yeah it could have been literally anything no the floppy bath might have to see whatever its official name is maybe it's got a counterpart in the sky I mean it takes a long time for wings to develop so but it's light enough it just kind of floats around like like a jellyfish but of the air yeah it's like um spiders can
travel using sort of electrostatic currents in the air so when they make their their parachuti web things they're not catching a breeze they're catching a letter static interactions so maybe there's a floaty bath mat thing that was doing that way back when I hope so I hope so uh I feel like we're just making well we are literally making things up now so probably time to call it a day having stopped doing the science yeah so you're essentially saying like we can
chase our ancestry back to around about five and a half million years ago when things started to take off in the biodiversity world and we probably owe a lot to those changing conditions and that there are animals that are somehow survived despite all of these changing conditions since then that we can still recognize in that quite ancient Rock record yeah absolutely cool and there are lots of funky sounding pictures that you can probably look up and I guess we'll share on social media oh yeah
absolutely Google Canberra and explosion animals because that is a wild ride oh there you go something to do on a rainy Sunday afternoon and I guess we'll pick up some of the stuff like paleo botany is that a thing absolutely I'm sure it's a thing yeah people want to know about when plants got good that can be a future episode yeah there you go let us know if you'd like to hear that and stay tuned see what happens next we'll see you then the views expressed in this podcast
belong entirely to the person that said them they do not represent any industry or organization if you enjoyed listening to these views it would really help us out if you could rate US leave a review and tell a friend this podcast was sponsored by no one but if you're interested in funding us to continue to have Frank discussions about science and engineering please get in touch [Music]