Evolution before Darwin

Welcome to the BioAudio Podcast. Today a colleague and I discuss evolutionary thought in the time before Darwin. Hi I'm Mark Vikari and I teach biology at York at several different levels in the ecology and evolution stream. Okay so we're going to start the discussion today almost at the beginning of recorded European history and the idea of this is to discuss what was known about evolution, what was debated about the process of change in lineages before Darwin because lots of students come in with this concept that Darwin invented evolution when in fact he's never been credited with that and it has been talked about before he came along. So let's go way back and start with ancient Greeks because that's mostly this is European history we'll try to talk about some non-European individuals. What were the Greeks debating? The idea of evolution goes back well into ancient Greece and there were a number of different philosophers that speculated about the possibility that life could evolve and other ideas were not particularly influential but they were definitely thinking about evolution long before Darwin. One of the earliest was an axiomander who lived in the sixth century BC. He argued that life originated in the oceans or at least originated in water and that humans were descended from aquatic ancestors and that the land was colonized after the oceans which is essentially correct but his ideas were considered very speculative. He didn't have much evidence to back those up so his ideas were not widely embraced but he was essentially proposing that life evolved from aquatic ancestors as far back as the sixth century BC. A little bit more recently in the fifth century BC and pedocles was another philosopher who speculated about evolution. He argued life forms were originally formed through a sort of a random process where different pieces kind of came together in a kind of experimentation and that the successful forms survived and the ones that were not successful died out which is an idea that's very similar to the mechanism of evolution proposed by Darwin which is evolution by natural selection. The idea that different life forms are created through processes that are random and then that the variation that's generated is edited and the most successful forms are the ones that survive so it was an idea very similar to Darwin theory of natural selection. So even two and a half thousand years ago we have prominent philosophers talking about the natural origin of life evolution that arose in oceans or at least in moisture. Did they debate the other side as well that this was static or was there really a feeling in ancient Greece that things were changing? Yes there was another side and that side was actually much more influential on Western thinking for a very long time. Plato came along about 50 years after him pedocles and he had a theory about the universe had implications for many different disciplines including biology that's his two world theory or theory of forms as it's also known. Plato argued that the world that we see around us is really an illusion. It's a distorted reflection of a more perfect world which we're not able to perceive with our senses. So for instance in nature we see one of the examples of circular shapes and various geometric forms but they're usually not perfect. We don't see perfect circles that are described to buy the mathematical equations of a circle perfectly. Plato argued that this was because what we're seeing is really just a shadow of the real circle which exists in the perfect world which we're not able to perceive directly. We're just seeing kind of a distorted reflection of that perfection in a kind of parallel universe which is sort of casting a shadow into our universe or a shadow that we're able to see. And he used this idea to explain variation in species for instance. If you look at cats obviously cats come in many different shapes and sizes, different colors, different hair lengths and so on. Plato would have argued that this variation is the result of many different distorted shadows being cast by the perfect cat that exists in this imperceptible perfect world that that's the real cat and the different cats that we see are just distorted reflections of that one individual. So although Plato's theory doesn't directly address the idea of evolution, it does imply that perfect creatures already exist. And if that's the case then why would there be a need for anything to evolve? It sort of implies that evolution doesn't exist because things are already perfect. But it also allows for individual variation. It explains why we don't all look identical. He's got a nice little neat way of saying it's just an error of what you are reflected as. You're really all the same but you're seeing these errors. Yes, absolutely. And of course that variation is very important in our current understanding of evolution. But Plato had an alternative explanation for why that variation exists. Now 50 years after that Aristotle had an even more very restricted way of viewing individuals and species with his ladder of nature. Aristotle was a student of Plato's and he kind of expanded on Plato's ideas. He proposed a classification system for living things, which is the ladder of nature that you mentioned. He argued that creatures were deliberately created to fill a specific position in this ladder and that they were sort of perfectly created for different roles, but they weren't all equally perfect. By that he was really referring to their level of complexity. He argued that more complex organisms were more perfect than simpler organisms and that there was a sort of a hierarchy in nature from the least perfect simplest organisms to the most perfect complex organisms and that creatures were created deliberately to fill a position within this hierarchy. Essentially there were no vacancies within this ladder. Every position was already occupied. So once again, the implication is that there's no evolution because creatures have been deliberately created to fill a specific position or role in nature. Okay, so you've then got this debate amongst prominent Greek philosophers between those that are arguing effectively for a gradual change or an evolution concept and those who are arguing for a static perfect entity concept, which is interestingly the same debate that goes on for the rest of everything we know about European history. We're still having that debate to a certain extent with the creationists versus evolutionists debate. So as far back as the Greek philosophers, we've got to have a debate of essentially going back and forth between these. I've read about a 9th century Iraqi scholar to show that this is not a European debate. He was arguing for effectively the struggle, which sounds a lot like natural selection as well. And this concept that there was a struggle for existence and the winners of the struggle went on to survive. So it's intriguing that we see this same debate being reflected in other cultures. So if we jump ahead many centuries, we end up in Europe in the natural theology, which we talk about a lot. This is sort of sets the stage for where Darwin would have come from. But what was the natural theology of Europe? Yes, so this was an idea that kind of dominated science in general in the 18th and 19th centuries. And it was the notion that by studying the natural world can gain an insight into the mind of God or we can understand God better by looking at the things that God has created. There was a strong tie between science and religion as a result of that sort of overarching view. Many people who were scientists were also clergymen. That was the usual way that you would become a scientist. You would you would become a clergyman and have a specialization like botany or zoology or something like that. So science and religion were closely tied together because of this idea that the reason to pursue science is to better understand the mind of God and to better understand God's thinking. It's quite interesting then that there was this idea that science and religion were almost the same subject at the time, whereas now they're actually viewed quite separately and the biggest debates in the field go on between the religious communities and the scientific communities. So it's intriguing that in a very short space of time they went from being effectively the same discipline to disciplines that are very much at odds. That's right. Science probably wouldn't have developed in the way that it did if it wasn't for that original nurturing through religious bodies and religious. So we have a scenario then where you really can't be a scientist without also being a religious clergyman. That there is an assumption that you are doing science to better understand God or at least biology to better understand God because you're looking at God's creation. And then you get a series of individuals who begin to challenge the orthodoxy or statements of the church in Europe and begin to question some of the things like timelines that the Bible has laid out for the scientists to work with. Let's talk about a few of them. So Georges Cuvier in the 17 1800s, he's a French paleontologist. He has a very significant impact on our understanding of potentially old life. What did he contribute? Yes, he was a professor of paleontology and he made some very important observations about fossils, which of course are a major source of information that we now have about how evolution has occurred and how life has changed over time. So he made some early observations about the way fossils are distributed which are very important. For one thing, he noted that fossils occur in sedimentary rocks, which are rocks that usually form underwater. And that within these rocks, we can see bands produced by different layers of sediment as they're laid down. And these are referred to as a strata. These different bands, we call them strata. So he noted that fossils tend to occur in these strata and that each strata seems to have its own distinct assemblage of fossils. So if we look at the fossils that are found in a particular band, we see that they are distinct, a distinct collection of fossils in that band compared with the bands that are higher or lower in the rock profile. So each stratum seems to have a distinct set of fossils. And furthermore, he noted that the further down you go in a rock profile, so the older the stratum that you're examining, the more different the fossils seem to be from modern day organisms. They start to look more and more different as you go further down and therefore further back in time. So he noticed these patterns about how fossils are distributed, but he did not interpret this, however, as evidence of evolution. Rather, he proposed a theory known as catastrophism in which he argued that natural disasters periodically wipe out species. And then those species are replaced either by immigration from the surroundings, or in some cases new species might be created supernaturally to replace those that are periodically wiped out. That was essentially how we argued that this turnover takes place in fossils. He didn't actually interpret the change through time as evidence of evolution. We have to give him some credit for the fact that he didn't have many fossils to go on at the time. So the detection of a transitional form would have been virtually impossible. It's not a bad assumption to make then that you've got things that simply disappear, not that you're having things change. Absolutely, yes. This is a fairly significant contribution that he made, this idea that things could go extinct. That was a relatively new concept compared to the idea that things were created perfectly and persist unchanged forever by the will of a God. This concept that something could actually be removed from that hierarchy of organisms created is really quite a significant contribution to that field. At the same time as Cuvier, we have someone called James Hutton. He's a geologist. He's active at the same time. What did he contribute to this wealth of knowledge? He proposed that geological processes are very slow and that the features of the landscape that we see around us are created by these slow processes that have a cumulative effect over time. So for instance, if you look at a feature like the Grand Canyon, he argued that the canyon was created by slow erosion from the river that runs through it over a period of millions of years. So we have this slow, constant process creating subtle change that's not very visible from one person's lifetime to another, but over time this change accumulates and ultimately has a very dramatic effect, which is the creation of the the Grand Canyon. So this was an idea that originally he developed for geology, but it was very influential in the thinking of people like Darwin who took this idea of slow gradual change having a dramatic long-term outcome and applied it in their theories of evolution. But I suppose the other thing it does is it provides for more time. If you've got this gradual change and he's arguing it could take very long time stretches to build up some of these formations, then some of the Bible literalism around creation occurring at a given date and time and the entire existence of the world being about 6000 years, he's making an argument for that time scale to be much, much bigger. That's absolutely right and that obviously is important for evolution to work. You need those very long time scales and that was a source of conflict between Hutton and the church, which as you mentioned argued that the world was only about 6000 years old based on the work that biblical scholars had done looking at the generations that had passed since Adam and Eve. Now at the same time as Kuvye and Hutton were active as effectively geologists in a totally unrelated field, we've got Thomas Malthus who's an economist and he has no direct connection to any of these players, but he advanced an idea which we think was probably fundamental to setting Darwin up for some of the things that he began to think about. What was it that Malthus was doing? A Malthus was interested in human population growth and he wrote an essay on the principle of population with Darwin red and had a big impact on Darwin's thinking, but in this essay Malthus argued that the human population was capable of growing much more rapidly than the environment could support. So essentially we could double our numbers every 25 years relatively easily, but there simply isn't enough food and other resources to support that rate of population growth. Therefore we have wars and famine and disease that keep the population in check. Darwin read about this and realized that the argument was even more applicable to the natural world because many species have a much greater capacity for reproduction than we have and therefore there must be even more intense competition for those limited resources among those individuals that are born and only it's a small fraction of those will actually survive to reproduce themselves. So that was an idea that Darwin got from Malthus, this idea that limiting resources ultimately create competition and most individuals that are born don't actually survive to reproduce. And Malthus would have been looking around at a European society where famine was something that people worried about. There were food riots at the time. There was an obvious limited supply of food-based resources and people starved. At the time of Malthus he would have witnessed people starving to death. That's right. The point that he was trying to make with this essay was that governments should not try to help the poor because if you give them more food for instance then the numbers will increase and will be right back where we started with a lack of food once again just because you know you give resources that promotes more population growth and ultimately you're back where you started. That was Malthus's sort of political intention in writing this. But Darwin realized that it had these implications for the natural world that were perhaps more sound than the original purpose of the paper. So he wasn't interested in social welfare? That's right. That's right. Now slightly later than these three is someone who is extraordinarily influential to Darwin and in fact a great friend of Darwin, which is Charles Liel. Liel was even one of the ones who helped Darwin eventually publish a lot of his work. What is it that Liel himself contributed that Darwin found so captivating? Liel's theory was essentially sort of an elaboration of Hutton's earlier theory about gradualism or he kind of built on that and he came up with a theory which we now call uniformitarianism which is the idea that if we want to understand why things are the way they are in the present we should look at the processes that are operating right now and extrapolate those back into the past. The idea that those processes have been uniform through time and we can understand how mountains form and canyons and so on by looking at the processes that are taking place today like erosion and glaciation and just assume that those processes have been the same through time. This was very influential in biology, the notion that we can understand how things are the way they are by looking at processes that we can see today in extrapolating backwards. I actually heard a story once that that Liel had written a three-part book series and Darwin had only read the first two when he set off on the Beagle and he was so captivated by them that he arranged for the third one to chase him partway around the world so he could get a copy of it right away. He wasn't willing to wait until he got back to England to get his copy of the third part of this series. It actually was sent to him on the Beagle so he could continue to read Liel while he was traveling. So if we combine the ideas of Hutton and Malthus and Liel, we have the earth must be very old that there have been slow subtle processes occurring over long periods of time which can have dramatic effects at least in geology and then this economic argument that a scarcity of resources will effectively generate competition for those resources and the suggestion that those who survive survive because they have an advantage or a Darwin would say better adapted to that survival. Malthus didn't quite go that far but it's interesting that those ideas were absolutely being discussed before Darwin even left on the Beagle that this is very pre-Darwin discussion. The last player who's usually mentioned in this context is a contemporary of Darwin and someone whom Darwin actually thought had a lot of very good ideas and that's Jean-Baptiste Delamarck. What did he argue in this field? Lamarck, he was a paleontologist like Cuvier. He also noted this pattern through time which Cuvier had noted earlier which was that fossils from more ancient rock stratus seem to be more different from modern day organisms than fossils from more recent stratus. Lamarck interpreted this differently from Cuvier. He saw this as evidence of biological change through time essentially he saw it as evidence of evolution. He proposed that species change by developing adaptations to their environment and that is the reason why we see this change over time. That sounds an awful lot like what Darwin actually advanced. This gradual change in response to an environment and these adaptations could lead to evolution but there's a crucial difference between the two of them and Darwin didn't dismiss Lamarck's ideas. I think he actually wrote in later life that Lamarck's ideas may very well be part of the whole theory but what was it that differentiated Darwin's explanation from Lamarck's explanation? Lamarck did propose that species change over time and he proposed that that change occurred as a result of adaptation to the environment but he got the mechanism of change wrong. He thought that individuals could acquire specific traits during their lifetime and then pass those on to their offspring. For example, Lamarck's theory suggests that if a weightlifter works out in the gym and develops big muscles and then they have a child that they could pass that muscle development on to their child so the child would be born with muscles that were more well developed than your typical baby and of course that's not the case. The child of a bodybuilder might have the same genetic potential to develop large muscles but they're still going to have to go to the gym and work out in order to get them. So the idea that you can acquire a trait in your lifetime and then pass that onto your offspring was an important part of Lamarck's explanation for why evolution occurred and he referred to it as inheritance of acquired characteristics and intuitively it's a very appealing idea that seemed to explain quite a lot but we now know that that's not how inheritance works and in fact there was a scientist Auguste De Weissmann who was a contemporary of Darwin who actually tested Lamarck's theory so it was not immediately dismissed. There were efforts to try and confirm Lamarck's ideas about why evolution occurred but Lamarck does deserve credit for at least acknowledging that evolution is real and for suggesting that evolution results in adaptations. Both of those ideas are things that that he and Darwin would be in complete agreement about. Darwin also didn't really understand how traits were acquired. He didn't have any knowledge about how inheritance works so it really was an active area of research and I think it's also true that both of them effectively got the mechanism of passing information down incorrect because neither of them had any concept of DNA. That was not part of the discussion. They didn't understand it. Nobody had read or met Mendel at that point who was independently coming up with the explanation without the theory behind it. You have to give Lamarck some credit. He could equally have been right. Neither one of them understood why the other was right or wrong. In later life Darwin still didn't understand that and knew that his own explanation for the transmission of information didn't work and argued that Lamarck could very well be correct and some level both seem like plausible explanations. Darwin just happened to latch on to the right one. That's right. It's interesting that you mentioned Mendel because Darwin did several subsequent editions of his book on the origin of species to try and get around this problem of blending inheritance which was the theory about inheritance that was very in the 19th century. The argument sort of goes if you have an individual that's born with a trade which is advantageous even if that trade is favored eventually that individual has to mate with some other individual in the population which is going to result in that trade being diluted out of existence over time. Mendel's experiments showed that that's not how inheritance works. It's unfortunate that Darwin didn't read that paper because he probably could have saved himself a lot of sleepless nights if he had but yes. So Darwin didn't understand how inheritance works but he did observe that that variation exists and that offspring resemble their parents and even without any knowledge of DNA he was still able to put forward an explanation for how evolutionary change occurs and how it creates adaptation that has survived all of the discoveries that we've made since then about DNA and the mechanisms of inheritance. Blending inheritance is often stated as Darwin's biggest blunder this idea and I think the classic sort of metaphor for it is if you're in the Arctic and you have a population whose coat color of is all brown and a single individual is born with a mutation that makes them white and therefore perfectly camouflaged their environment. They do really well but once they breed with one of the dark colored individuals they're offspring are only half as camouflaged and if they breed into the population the next generations even less well adapted for that white environment. And so Darwin couldn't explain how a rare new mutation could persist because his own mechanism suggests that it should be reduced with each generation being rare was not a good thing in his example. We now know of course things like recessive genes can pop up and you can you can just have these traits exist for a long period of time without being blended out of existence but Darwin knew it was wrong a lot of his friends told him it was wrong he just couldn't figure out what was right to replace it with and so he made arguments for a long time for something that he knew fundamentally didn't work but he couldn't figure out solution to it. That's right you'd almost have to argue that lots and lots of these mutations would have to occur simultaneously to avoid being diluted out of existence and since mutations are rare that seems like that in itself would almost require a divine act for all these simultaneous mutations to appear. Mendel had solved it and unfortunately Mendel wrote in German and Darwin never got the paper translated even though apparently he did have a copy of it in his possession. So it sounds like though if we think about the world as it existed basically before Darwin began to publish anything or before he even was interested in the field that we got literally thousands of years of people arguing back and forth between the perfect creation versus slow gradual change even in the immediate years before Darwin became an active member of this research community there were people effectively discussing all of the same things that he would go on to argue it the difference being that he put it all together into one piece of information with evidence and with carefully cataloged observations prior to that the theories were not particularly novel they were out there I think even Darwin's grandfather had written about evolution arasement Darwin had written papers on evolution just without any explanation of how it worked and no evidence maybe Darwin's emergence into this was inevitable or someone like him was going to come out and write about this and in fact multiple people were simultaneously arguing very very similar things the important message for students coming into these courses is that Darwin didn't have some a massive flash of insight and wrote a book about it it was it was in fact a well-known set of theories out there he just came up with evidence for it that's right yes and he he made it understandable to the public as well which I think was an important part of why he's remembered as the main author of the theory of natural selection because he wrote this huge book that was widely read presented an argument that most people could understand relatively relatively clearly whereas others such as Alfred Russell Wallace for example who basically came up with the same theory of natural selection at roughly the same time he he published a short academic paper which was considered very speculative and was not widely read so even though they came up with the idea of the same time Darwin is the one is remembered as as the main author of the theory yes we I we should remember that Darwin was an incredibly popular author that was one of his main sources of income as an adult after he returned from his trip around the world was as a writer so he was very well known as a published author writing work that was read widely within society not just amongst academics or what we would now call academics the the sort of the average person was probably reading Darwin so that gave him a a slight advantage in the publication game that he knew how to pitch and explain ideas to people on mass and he was a popular scientist at that point a popular science writer we would call him now I'd like to thank Mark Fakari for joining me today on bio audio podcast thanks for listening to the bio audio podcast the bio audio project was started to provide a free alternative to textbooks for students and educators to provide a more inclusive resource and one we can add new topics to at any time and modify if you are a student and you have enjoyed this episode send me a note on twitter at doctor underscore bat underscore girl or on maston at professor bat girl at eco evo dot social and follow me to hear when new episodes are posted if you are a university educator when like to use the content please feel free and let me know you're making use of it ask your students to follow the podcast if you would like to suggest a new episode and better yet help me make it send a message on twitter maston or to bio audio one at gmail.com I'm happy to make new content to fit other courses and I'll prioritize a topic if you can help me record it